before send to remote

env/lib/python3.8/site-packages/django/db/backends/sqlite3/_functions.py

@@ -0,0 +1,512 @@
+"""
+Implementations of SQL functions for SQLite.
+"""
+import functools
+import random
+import statistics
+from datetime import timedelta
+from hashlib import sha1, sha224, sha256, sha384, sha512
+from math import (
+    acos,
+    asin,
+    atan,
+    atan2,
+    ceil,
+    cos,
+    degrees,
+    exp,
+    floor,
+    fmod,
+    log,
+    pi,
+    radians,
+    sin,
+    sqrt,
+    tan,
+)
+from re import search as re_search
+
+from django.db.backends.base.base import timezone_constructor
+from django.db.backends.utils import (
+    split_tzname_delta,
+    typecast_time,
+    typecast_timestamp,
+)
+from django.utils import timezone
+from django.utils.crypto import md5
+from django.utils.duration import duration_microseconds
+
+
+def register(connection):
+    create_deterministic_function = functools.partial(
+        connection.create_function,
+        deterministic=True,
+    )
+    create_deterministic_function("django_date_extract", 2, _sqlite_datetime_extract)
+    create_deterministic_function("django_date_trunc", 4, _sqlite_date_trunc)
+    create_deterministic_function(
+        "django_datetime_cast_date", 3, _sqlite_datetime_cast_date
+    )
+    create_deterministic_function(
+        "django_datetime_cast_time", 3, _sqlite_datetime_cast_time
+    )
+    create_deterministic_function(
+        "django_datetime_extract", 4, _sqlite_datetime_extract
+    )
+    create_deterministic_function("django_datetime_trunc", 4, _sqlite_datetime_trunc)
+    create_deterministic_function("django_time_extract", 2, _sqlite_time_extract)
+    create_deterministic_function("django_time_trunc", 4, _sqlite_time_trunc)
+    create_deterministic_function("django_time_diff", 2, _sqlite_time_diff)
+    create_deterministic_function("django_timestamp_diff", 2, _sqlite_timestamp_diff)
+    create_deterministic_function("django_format_dtdelta", 3, _sqlite_format_dtdelta)
+    create_deterministic_function("regexp", 2, _sqlite_regexp)
+    create_deterministic_function("BITXOR", 2, _sqlite_bitxor)
+    create_deterministic_function("COT", 1, _sqlite_cot)
+    create_deterministic_function("LPAD", 3, _sqlite_lpad)
+    create_deterministic_function("MD5", 1, _sqlite_md5)
+    create_deterministic_function("REPEAT", 2, _sqlite_repeat)
+    create_deterministic_function("REVERSE", 1, _sqlite_reverse)
+    create_deterministic_function("RPAD", 3, _sqlite_rpad)
+    create_deterministic_function("SHA1", 1, _sqlite_sha1)
+    create_deterministic_function("SHA224", 1, _sqlite_sha224)
+    create_deterministic_function("SHA256", 1, _sqlite_sha256)
+    create_deterministic_function("SHA384", 1, _sqlite_sha384)
+    create_deterministic_function("SHA512", 1, _sqlite_sha512)
+    create_deterministic_function("SIGN", 1, _sqlite_sign)
+    # Don't use the built-in RANDOM() function because it returns a value
+    # in the range [-1 * 2^63, 2^63 - 1] instead of [0, 1).
+    connection.create_function("RAND", 0, random.random)
+    connection.create_aggregate("STDDEV_POP", 1, StdDevPop)
+    connection.create_aggregate("STDDEV_SAMP", 1, StdDevSamp)
+    connection.create_aggregate("VAR_POP", 1, VarPop)
+    connection.create_aggregate("VAR_SAMP", 1, VarSamp)
+    # Some math functions are enabled by default in SQLite 3.35+.
+    sql = "select sqlite_compileoption_used('ENABLE_MATH_FUNCTIONS')"
+    if not connection.execute(sql).fetchone()[0]:
+        create_deterministic_function("ACOS", 1, _sqlite_acos)
+        create_deterministic_function("ASIN", 1, _sqlite_asin)
+        create_deterministic_function("ATAN", 1, _sqlite_atan)
+        create_deterministic_function("ATAN2", 2, _sqlite_atan2)
+        create_deterministic_function("CEILING", 1, _sqlite_ceiling)
+        create_deterministic_function("COS", 1, _sqlite_cos)
+        create_deterministic_function("DEGREES", 1, _sqlite_degrees)
+        create_deterministic_function("EXP", 1, _sqlite_exp)
+        create_deterministic_function("FLOOR", 1, _sqlite_floor)
+        create_deterministic_function("LN", 1, _sqlite_ln)
+        create_deterministic_function("LOG", 2, _sqlite_log)
+        create_deterministic_function("MOD", 2, _sqlite_mod)
+        create_deterministic_function("PI", 0, _sqlite_pi)
+        create_deterministic_function("POWER", 2, _sqlite_power)
+        create_deterministic_function("RADIANS", 1, _sqlite_radians)
+        create_deterministic_function("SIN", 1, _sqlite_sin)
+        create_deterministic_function("SQRT", 1, _sqlite_sqrt)
+        create_deterministic_function("TAN", 1, _sqlite_tan)
+
+
+def _sqlite_datetime_parse(dt, tzname=None, conn_tzname=None):
+    if dt is None:
+        return None
+    try:
+        dt = typecast_timestamp(dt)
+    except (TypeError, ValueError):
+        return None
+    if conn_tzname:
+        dt = dt.replace(tzinfo=timezone_constructor(conn_tzname))
+    if tzname is not None and tzname != conn_tzname:
+        tzname, sign, offset = split_tzname_delta(tzname)
+        if offset:
+            hours, minutes = offset.split(":")
+            offset_delta = timedelta(hours=int(hours), minutes=int(minutes))
+            dt += offset_delta if sign == "+" else -offset_delta
+        dt = timezone.localtime(dt, timezone_constructor(tzname))
+    return dt
+
+
+def _sqlite_date_trunc(lookup_type, dt, tzname, conn_tzname):
+    dt = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt is None:
+        return None
+    if lookup_type == "year":
+        return f"{dt.year:04d}-01-01"
+    elif lookup_type == "quarter":
+        month_in_quarter = dt.month - (dt.month - 1) % 3
+        return f"{dt.year:04d}-{month_in_quarter:02d}-01"
+    elif lookup_type == "month":
+        return f"{dt.year:04d}-{dt.month:02d}-01"
+    elif lookup_type == "week":
+        dt = dt - timedelta(days=dt.weekday())
+        return f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d}"
+    elif lookup_type == "day":
+        return f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d}"
+    raise ValueError(f"Unsupported lookup type: {lookup_type!r}")
+
+
+def _sqlite_time_trunc(lookup_type, dt, tzname, conn_tzname):
+    if dt is None:
+        return None
+    dt_parsed = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt_parsed is None:
+        try:
+            dt = typecast_time(dt)
+        except (ValueError, TypeError):
+            return None
+    else:
+        dt = dt_parsed
+    if lookup_type == "hour":
+        return f"{dt.hour:02d}:00:00"
+    elif lookup_type == "minute":
+        return f"{dt.hour:02d}:{dt.minute:02d}:00"
+    elif lookup_type == "second":
+        return f"{dt.hour:02d}:{dt.minute:02d}:{dt.second:02d}"
+    raise ValueError(f"Unsupported lookup type: {lookup_type!r}")
+
+
+def _sqlite_datetime_cast_date(dt, tzname, conn_tzname):
+    dt = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt is None:
+        return None
+    return dt.date().isoformat()
+
+
+def _sqlite_datetime_cast_time(dt, tzname, conn_tzname):
+    dt = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt is None:
+        return None
+    return dt.time().isoformat()
+
+
+def _sqlite_datetime_extract(lookup_type, dt, tzname=None, conn_tzname=None):
+    dt = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt is None:
+        return None
+    if lookup_type == "week_day":
+        return (dt.isoweekday() % 7) + 1
+    elif lookup_type == "iso_week_day":
+        return dt.isoweekday()
+    elif lookup_type == "week":
+        return dt.isocalendar()[1]
+    elif lookup_type == "quarter":
+        return ceil(dt.month / 3)
+    elif lookup_type == "iso_year":
+        return dt.isocalendar()[0]
+    else:
+        return getattr(dt, lookup_type)
+
+
+def _sqlite_datetime_trunc(lookup_type, dt, tzname, conn_tzname):
+    dt = _sqlite_datetime_parse(dt, tzname, conn_tzname)
+    if dt is None:
+        return None
+    if lookup_type == "year":
+        return f"{dt.year:04d}-01-01 00:00:00"
+    elif lookup_type == "quarter":
+        month_in_quarter = dt.month - (dt.month - 1) % 3
+        return f"{dt.year:04d}-{month_in_quarter:02d}-01 00:00:00"
+    elif lookup_type == "month":
+        return f"{dt.year:04d}-{dt.month:02d}-01 00:00:00"
+    elif lookup_type == "week":
+        dt = dt - timedelta(days=dt.weekday())
+        return f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d} 00:00:00"
+    elif lookup_type == "day":
+        return f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d} 00:00:00"
+    elif lookup_type == "hour":
+        return f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d} {dt.hour:02d}:00:00"
+    elif lookup_type == "minute":
+        return (
+            f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d} "
+            f"{dt.hour:02d}:{dt.minute:02d}:00"
+        )
+    elif lookup_type == "second":
+        return (
+            f"{dt.year:04d}-{dt.month:02d}-{dt.day:02d} "
+            f"{dt.hour:02d}:{dt.minute:02d}:{dt.second:02d}"
+        )
+    raise ValueError(f"Unsupported lookup type: {lookup_type!r}")
+
+
+def _sqlite_time_extract(lookup_type, dt):
+    if dt is None:
+        return None
+    try:
+        dt = typecast_time(dt)
+    except (ValueError, TypeError):
+        return None
+    return getattr(dt, lookup_type)
+
+
+def _sqlite_prepare_dtdelta_param(conn, param):
+    if conn in ["+", "-"]:
+        if isinstance(param, int):
+            return timedelta(0, 0, param)
+        else:
+            return typecast_timestamp(param)
+    return param
+
+
+def _sqlite_format_dtdelta(connector, lhs, rhs):
+    """
+    LHS and RHS can be either:
+    - An integer number of microseconds
+    - A string representing a datetime
+    - A scalar value, e.g. float
+    """
+    if connector is None or lhs is None or rhs is None:
+        return None
+    connector = connector.strip()
+    try:
+        real_lhs = _sqlite_prepare_dtdelta_param(connector, lhs)
+        real_rhs = _sqlite_prepare_dtdelta_param(connector, rhs)
+    except (ValueError, TypeError):
+        return None
+    if connector == "+":
+        # typecast_timestamp() returns a date or a datetime without timezone.
+        # It will be formatted as "%Y-%m-%d" or "%Y-%m-%d %H:%M:%S[.%f]"
+        out = str(real_lhs + real_rhs)
+    elif connector == "-":
+        out = str(real_lhs - real_rhs)
+    elif connector == "*":
+        out = real_lhs * real_rhs
+    else:
+        out = real_lhs / real_rhs
+    return out
+
+
+def _sqlite_time_diff(lhs, rhs):
+    if lhs is None or rhs is None:
+        return None
+    left = typecast_time(lhs)
+    right = typecast_time(rhs)
+    return (
+        (left.hour * 60 * 60 * 1000000)
+        + (left.minute * 60 * 1000000)
+        + (left.second * 1000000)
+        + (left.microsecond)
+        - (right.hour * 60 * 60 * 1000000)
+        - (right.minute * 60 * 1000000)
+        - (right.second * 1000000)
+        - (right.microsecond)
+    )
+
+
+def _sqlite_timestamp_diff(lhs, rhs):
+    if lhs is None or rhs is None:
+        return None
+    left = typecast_timestamp(lhs)
+    right = typecast_timestamp(rhs)
+    return duration_microseconds(left - right)
+
+
+def _sqlite_regexp(pattern, string):
+    if pattern is None or string is None:
+        return None
+    if not isinstance(string, str):
+        string = str(string)
+    return bool(re_search(pattern, string))
+
+
+def _sqlite_acos(x):
+    if x is None:
+        return None
+    return acos(x)
+
+
+def _sqlite_asin(x):
+    if x is None:
+        return None
+    return asin(x)
+
+
+def _sqlite_atan(x):
+    if x is None:
+        return None
+    return atan(x)
+
+
+def _sqlite_atan2(y, x):
+    if y is None or x is None:
+        return None
+    return atan2(y, x)
+
+
+def _sqlite_bitxor(x, y):
+    if x is None or y is None:
+        return None
+    return x ^ y
+
+
+def _sqlite_ceiling(x):
+    if x is None:
+        return None
+    return ceil(x)
+
+
+def _sqlite_cos(x):
+    if x is None:
+        return None
+    return cos(x)
+
+
+def _sqlite_cot(x):
+    if x is None:
+        return None
+    return 1 / tan(x)
+
+
+def _sqlite_degrees(x):
+    if x is None:
+        return None
+    return degrees(x)
+
+
+def _sqlite_exp(x):
+    if x is None:
+        return None
+    return exp(x)
+
+
+def _sqlite_floor(x):
+    if x is None:
+        return None
+    return floor(x)
+
+
+def _sqlite_ln(x):
+    if x is None:
+        return None
+    return log(x)
+
+
+def _sqlite_log(base, x):
+    if base is None or x is None:
+        return None
+    # Arguments reversed to match SQL standard.
+    return log(x, base)
+
+
+def _sqlite_lpad(text, length, fill_text):
+    if text is None or length is None or fill_text is None:
+        return None
+    delta = length - len(text)
+    if delta <= 0:
+        return text[:length]
+    return (fill_text * length)[:delta] + text
+
+
+def _sqlite_md5(text):
+    if text is None:
+        return None
+    return md5(text.encode()).hexdigest()
+
+
+def _sqlite_mod(x, y):
+    if x is None or y is None:
+        return None
+    return fmod(x, y)
+
+
+def _sqlite_pi():
+    return pi
+
+
+def _sqlite_power(x, y):
+    if x is None or y is None:
+        return None
+    return x**y
+
+
+def _sqlite_radians(x):
+    if x is None:
+        return None
+    return radians(x)
+
+
+def _sqlite_repeat(text, count):
+    if text is None or count is None:
+        return None
+    return text * count
+
+
+def _sqlite_reverse(text):
+    if text is None:
+        return None
+    return text[::-1]
+
+
+def _sqlite_rpad(text, length, fill_text):
+    if text is None or length is None or fill_text is None:
+        return None
+    return (text + fill_text * length)[:length]
+
+
+def _sqlite_sha1(text):
+    if text is None:
+        return None
+    return sha1(text.encode()).hexdigest()
+
+
+def _sqlite_sha224(text):
+    if text is None:
+        return None
+    return sha224(text.encode()).hexdigest()
+
+
+def _sqlite_sha256(text):
+    if text is None:
+        return None
+    return sha256(text.encode()).hexdigest()
+
+
+def _sqlite_sha384(text):
+    if text is None:
+        return None
+    return sha384(text.encode()).hexdigest()
+
+
+def _sqlite_sha512(text):
+    if text is None:
+        return None
+    return sha512(text.encode()).hexdigest()
+
+
+def _sqlite_sign(x):
+    if x is None:
+        return None
+    return (x > 0) - (x < 0)
+
+
+def _sqlite_sin(x):
+    if x is None:
+        return None
+    return sin(x)
+
+
+def _sqlite_sqrt(x):
+    if x is None:
+        return None
+    return sqrt(x)
+
+
+def _sqlite_tan(x):
+    if x is None:
+        return None
+    return tan(x)
+
+
+class ListAggregate(list):
+    step = list.append
+
+
+class StdDevPop(ListAggregate):
+    finalize = statistics.pstdev
+
+
+class StdDevSamp(ListAggregate):
+    finalize = statistics.stdev
+
+
+class VarPop(ListAggregate):
+    finalize = statistics.pvariance
+
+
+class VarSamp(ListAggregate):
+    finalize = statistics.variance

env/lib/python3.8/site-packages/django/db/backends/sqlite3/base.py

@@ -0,0 +1,364 @@
+"""
+SQLite backend for the sqlite3 module in the standard library.
+"""
+import decimal
+import warnings
+from itertools import chain
+from sqlite3 import dbapi2 as Database
+
+from django.core.exceptions import ImproperlyConfigured
+from django.db import IntegrityError
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.utils.asyncio import async_unsafe
+from django.utils.dateparse import parse_datetime, parse_time
+from django.utils.regex_helper import _lazy_re_compile
+
+from ._functions import register as register_functions
+from .client import DatabaseClient
+from .creation import DatabaseCreation
+from .features import DatabaseFeatures
+from .introspection import DatabaseIntrospection
+from .operations import DatabaseOperations
+from .schema import DatabaseSchemaEditor
+
+
+def decoder(conv_func):
+    """
+    Convert bytestrings from Python's sqlite3 interface to a regular string.
+    """
+    return lambda s: conv_func(s.decode())
+
+
+Database.register_converter("bool", b"1".__eq__)
+Database.register_converter("time", decoder(parse_time))
+Database.register_converter("datetime", decoder(parse_datetime))
+Database.register_converter("timestamp", decoder(parse_datetime))
+
+Database.register_adapter(decimal.Decimal, str)
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    vendor = "sqlite"
+    display_name = "SQLite"
+    # SQLite doesn't actually support most of these types, but it "does the right
+    # thing" given more verbose field definitions, so leave them as is so that
+    # schema inspection is more useful.
+    data_types = {
+        "AutoField": "integer",
+        "BigAutoField": "integer",
+        "BinaryField": "BLOB",
+        "BooleanField": "bool",
+        "CharField": "varchar(%(max_length)s)",
+        "DateField": "date",
+        "DateTimeField": "datetime",
+        "DecimalField": "decimal",
+        "DurationField": "bigint",
+        "FileField": "varchar(%(max_length)s)",
+        "FilePathField": "varchar(%(max_length)s)",
+        "FloatField": "real",
+        "IntegerField": "integer",
+        "BigIntegerField": "bigint",
+        "IPAddressField": "char(15)",
+        "GenericIPAddressField": "char(39)",
+        "JSONField": "text",
+        "OneToOneField": "integer",
+        "PositiveBigIntegerField": "bigint unsigned",
+        "PositiveIntegerField": "integer unsigned",
+        "PositiveSmallIntegerField": "smallint unsigned",
+        "SlugField": "varchar(%(max_length)s)",
+        "SmallAutoField": "integer",
+        "SmallIntegerField": "smallint",
+        "TextField": "text",
+        "TimeField": "time",
+        "UUIDField": "char(32)",
+    }
+    data_type_check_constraints = {
+        "PositiveBigIntegerField": '"%(column)s" >= 0',
+        "JSONField": '(JSON_VALID("%(column)s") OR "%(column)s" IS NULL)',
+        "PositiveIntegerField": '"%(column)s" >= 0',
+        "PositiveSmallIntegerField": '"%(column)s" >= 0',
+    }
+    data_types_suffix = {
+        "AutoField": "AUTOINCREMENT",
+        "BigAutoField": "AUTOINCREMENT",
+        "SmallAutoField": "AUTOINCREMENT",
+    }
+    # SQLite requires LIKE statements to include an ESCAPE clause if the value
+    # being escaped has a percent or underscore in it.
+    # See https://www.sqlite.org/lang_expr.html for an explanation.
+    operators = {
+        "exact": "= %s",
+        "iexact": "LIKE %s ESCAPE '\\'",
+        "contains": "LIKE %s ESCAPE '\\'",
+        "icontains": "LIKE %s ESCAPE '\\'",
+        "regex": "REGEXP %s",
+        "iregex": "REGEXP '(?i)' || %s",
+        "gt": "> %s",
+        "gte": ">= %s",
+        "lt": "< %s",
+        "lte": "<= %s",
+        "startswith": "LIKE %s ESCAPE '\\'",
+        "endswith": "LIKE %s ESCAPE '\\'",
+        "istartswith": "LIKE %s ESCAPE '\\'",
+        "iendswith": "LIKE %s ESCAPE '\\'",
+    }
+
+    # The patterns below are used to generate SQL pattern lookup clauses when
+    # the right-hand side of the lookup isn't a raw string (it might be an expression
+    # or the result of a bilateral transformation).
+    # In those cases, special characters for LIKE operators (e.g. \, *, _) should be
+    # escaped on database side.
+    #
+    # Note: we use str.format() here for readability as '%' is used as a wildcard for
+    # the LIKE operator.
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
+    pattern_ops = {
+        "contains": r"LIKE '%%' || {} || '%%' ESCAPE '\'",
+        "icontains": r"LIKE '%%' || UPPER({}) || '%%' ESCAPE '\'",
+        "startswith": r"LIKE {} || '%%' ESCAPE '\'",
+        "istartswith": r"LIKE UPPER({}) || '%%' ESCAPE '\'",
+        "endswith": r"LIKE '%%' || {} ESCAPE '\'",
+        "iendswith": r"LIKE '%%' || UPPER({}) ESCAPE '\'",
+    }
+
+    Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+
+    def get_connection_params(self):
+        settings_dict = self.settings_dict
+        if not settings_dict["NAME"]:
+            raise ImproperlyConfigured(
+                "settings.DATABASES is improperly configured. "
+                "Please supply the NAME value."
+            )
+        kwargs = {
+            "database": settings_dict["NAME"],
+            "detect_types": Database.PARSE_DECLTYPES | Database.PARSE_COLNAMES,
+            **settings_dict["OPTIONS"],
+        }
+        # Always allow the underlying SQLite connection to be shareable
+        # between multiple threads. The safe-guarding will be handled at a
+        # higher level by the `BaseDatabaseWrapper.allow_thread_sharing`
+        # property. This is necessary as the shareability is disabled by
+        # default in pysqlite and it cannot be changed once a connection is
+        # opened.
+        if "check_same_thread" in kwargs and kwargs["check_same_thread"]:
+            warnings.warn(
+                "The `check_same_thread` option was provided and set to "
+                "True. It will be overridden with False. Use the "
+                "`DatabaseWrapper.allow_thread_sharing` property instead "
+                "for controlling thread shareability.",
+                RuntimeWarning,
+            )
+        kwargs.update({"check_same_thread": False, "uri": True})
+        return kwargs
+
+    def get_database_version(self):
+        return self.Database.sqlite_version_info
+
+    @async_unsafe
+    def get_new_connection(self, conn_params):
+        conn = Database.connect(**conn_params)
+        register_functions(conn)
+
+        conn.execute("PRAGMA foreign_keys = ON")
+        # The macOS bundled SQLite defaults legacy_alter_table ON, which
+        # prevents atomic table renames (feature supports_atomic_references_rename)
+        conn.execute("PRAGMA legacy_alter_table = OFF")
+        return conn
+
+    def create_cursor(self, name=None):
+        return self.connection.cursor(factory=SQLiteCursorWrapper)
+
+    @async_unsafe
+    def close(self):
+        self.validate_thread_sharing()
+        # If database is in memory, closing the connection destroys the
+        # database. To prevent accidental data loss, ignore close requests on
+        # an in-memory db.
+        if not self.is_in_memory_db():
+            BaseDatabaseWrapper.close(self)
+
+    def _savepoint_allowed(self):
+        # When 'isolation_level' is not None, sqlite3 commits before each
+        # savepoint; it's a bug. When it is None, savepoints don't make sense
+        # because autocommit is enabled. The only exception is inside 'atomic'
+        # blocks. To work around that bug, on SQLite, 'atomic' starts a
+        # transaction explicitly rather than simply disable autocommit.
+        return self.in_atomic_block
+
+    def _set_autocommit(self, autocommit):
+        if autocommit:
+            level = None
+        else:
+            # sqlite3's internal default is ''. It's different from None.
+            # See Modules/_sqlite/connection.c.
+            level = ""
+        # 'isolation_level' is a misleading API.
+        # SQLite always runs at the SERIALIZABLE isolation level.
+        with self.wrap_database_errors:
+            self.connection.isolation_level = level
+
+    def disable_constraint_checking(self):
+        with self.cursor() as cursor:
+            cursor.execute("PRAGMA foreign_keys = OFF")
+            # Foreign key constraints cannot be turned off while in a multi-
+            # statement transaction. Fetch the current state of the pragma
+            # to determine if constraints are effectively disabled.
+            enabled = cursor.execute("PRAGMA foreign_keys").fetchone()[0]
+        return not bool(enabled)
+
+    def enable_constraint_checking(self):
+        with self.cursor() as cursor:
+            cursor.execute("PRAGMA foreign_keys = ON")
+
+    def check_constraints(self, table_names=None):
+        """
+        Check each table name in `table_names` for rows with invalid foreign
+        key references. This method is intended to be used in conjunction with
+        `disable_constraint_checking()` and `enable_constraint_checking()`, to
+        determine if rows with invalid references were entered while constraint
+        checks were off.
+        """
+        if self.features.supports_pragma_foreign_key_check:
+            with self.cursor() as cursor:
+                if table_names is None:
+                    violations = cursor.execute("PRAGMA foreign_key_check").fetchall()
+                else:
+                    violations = chain.from_iterable(
+                        cursor.execute(
+                            "PRAGMA foreign_key_check(%s)"
+                            % self.ops.quote_name(table_name)
+                        ).fetchall()
+                        for table_name in table_names
+                    )
+                # See https://www.sqlite.org/pragma.html#pragma_foreign_key_check
+                for (
+                    table_name,
+                    rowid,
+                    referenced_table_name,
+                    foreign_key_index,
+                ) in violations:
+                    foreign_key = cursor.execute(
+                        "PRAGMA foreign_key_list(%s)" % self.ops.quote_name(table_name)
+                    ).fetchall()[foreign_key_index]
+                    column_name, referenced_column_name = foreign_key[3:5]
+                    primary_key_column_name = self.introspection.get_primary_key_column(
+                        cursor, table_name
+                    )
+                    primary_key_value, bad_value = cursor.execute(
+                        "SELECT %s, %s FROM %s WHERE rowid = %%s"
+                        % (
+                            self.ops.quote_name(primary_key_column_name),
+                            self.ops.quote_name(column_name),
+                            self.ops.quote_name(table_name),
+                        ),
+                        (rowid,),
+                    ).fetchone()
+                    raise IntegrityError(
+                        "The row in table '%s' with primary key '%s' has an "
+                        "invalid foreign key: %s.%s contains a value '%s' that "
+                        "does not have a corresponding value in %s.%s."
+                        % (
+                            table_name,
+                            primary_key_value,
+                            table_name,
+                            column_name,
+                            bad_value,
+                            referenced_table_name,
+                            referenced_column_name,
+                        )
+                    )
+        else:
+            with self.cursor() as cursor:
+                if table_names is None:
+                    table_names = self.introspection.table_names(cursor)
+                for table_name in table_names:
+                    primary_key_column_name = self.introspection.get_primary_key_column(
+                        cursor, table_name
+                    )
+                    if not primary_key_column_name:
+                        continue
+                    relations = self.introspection.get_relations(cursor, table_name)
+                    for column_name, (
+                        referenced_column_name,
+                        referenced_table_name,
+                    ) in relations:
+                        cursor.execute(
+                            """
+                            SELECT REFERRING.`%s`, REFERRING.`%s` FROM `%s` as REFERRING
+                            LEFT JOIN `%s` as REFERRED
+                            ON (REFERRING.`%s` = REFERRED.`%s`)
+                            WHERE REFERRING.`%s` IS NOT NULL AND REFERRED.`%s` IS NULL
+                            """
+                            % (
+                                primary_key_column_name,
+                                column_name,
+                                table_name,
+                                referenced_table_name,
+                                column_name,
+                                referenced_column_name,
+                                column_name,
+                                referenced_column_name,
+                            )
+                        )
+                        for bad_row in cursor.fetchall():
+                            raise IntegrityError(
+                                "The row in table '%s' with primary key '%s' has an "
+                                "invalid foreign key: %s.%s contains a value '%s' that "
+                                "does not have a corresponding value in %s.%s."
+                                % (
+                                    table_name,
+                                    bad_row[0],
+                                    table_name,
+                                    column_name,
+                                    bad_row[1],
+                                    referenced_table_name,
+                                    referenced_column_name,
+                                )
+                            )
+
+    def is_usable(self):
+        return True
+
+    def _start_transaction_under_autocommit(self):
+        """
+        Start a transaction explicitly in autocommit mode.
+
+        Staying in autocommit mode works around a bug of sqlite3 that breaks
+        savepoints when autocommit is disabled.
+        """
+        self.cursor().execute("BEGIN")
+
+    def is_in_memory_db(self):
+        return self.creation.is_in_memory_db(self.settings_dict["NAME"])
+
+
+FORMAT_QMARK_REGEX = _lazy_re_compile(r"(?<!%)%s")
+
+
+class SQLiteCursorWrapper(Database.Cursor):
+    """
+    Django uses "format" style placeholders, but pysqlite2 uses "qmark" style.
+    This fixes it -- but note that if you want to use a literal "%s" in a query,
+    you'll need to use "%%s".
+    """
+
+    def execute(self, query, params=None):
+        if params is None:
+            return Database.Cursor.execute(self, query)
+        query = self.convert_query(query)
+        return Database.Cursor.execute(self, query, params)
+
+    def executemany(self, query, param_list):
+        query = self.convert_query(query)
+        return Database.Cursor.executemany(self, query, param_list)
+
+    def convert_query(self, query):
+        return FORMAT_QMARK_REGEX.sub("?", query).replace("%%", "%")

env/lib/python3.8/site-packages/django/db/backends/sqlite3/client.py

@@ -0,0 +1,10 @@
+from django.db.backends.base.client import BaseDatabaseClient
+
+
+class DatabaseClient(BaseDatabaseClient):
+    executable_name = "sqlite3"
+
+    @classmethod
+    def settings_to_cmd_args_env(cls, settings_dict, parameters):
+        args = [cls.executable_name, settings_dict["NAME"], *parameters]
+        return args, None

env/lib/python3.8/site-packages/django/db/backends/sqlite3/creation.py

@@ -0,0 +1,158 @@
+import multiprocessing
+import os
+import shutil
+import sqlite3
+import sys
+from pathlib import Path
+
+from django.db import NotSupportedError
+from django.db.backends.base.creation import BaseDatabaseCreation
+
+
+class DatabaseCreation(BaseDatabaseCreation):
+    @staticmethod
+    def is_in_memory_db(database_name):
+        return not isinstance(database_name, Path) and (
+            database_name == ":memory:" or "mode=memory" in database_name
+        )
+
+    def _get_test_db_name(self):
+        test_database_name = self.connection.settings_dict["TEST"]["NAME"] or ":memory:"
+        if test_database_name == ":memory:":
+            return "file:memorydb_%s?mode=memory&cache=shared" % self.connection.alias
+        return test_database_name
+
+    def _create_test_db(self, verbosity, autoclobber, keepdb=False):
+        test_database_name = self._get_test_db_name()
+
+        if keepdb:
+            return test_database_name
+        if not self.is_in_memory_db(test_database_name):
+            # Erase the old test database
+            if verbosity >= 1:
+                self.log(
+                    "Destroying old test database for alias %s..."
+                    % (self._get_database_display_str(verbosity, test_database_name),)
+                )
+            if os.access(test_database_name, os.F_OK):
+                if not autoclobber:
+                    confirm = input(
+                        "Type 'yes' if you would like to try deleting the test "
+                        "database '%s', or 'no' to cancel: " % test_database_name
+                    )
+                if autoclobber or confirm == "yes":
+                    try:
+                        os.remove(test_database_name)
+                    except Exception as e:
+                        self.log("Got an error deleting the old test database: %s" % e)
+                        sys.exit(2)
+                else:
+                    self.log("Tests cancelled.")
+                    sys.exit(1)
+        return test_database_name
+
+    def get_test_db_clone_settings(self, suffix):
+        orig_settings_dict = self.connection.settings_dict
+        source_database_name = orig_settings_dict["NAME"]
+
+        if not self.is_in_memory_db(source_database_name):
+            root, ext = os.path.splitext(source_database_name)
+            return {**orig_settings_dict, "NAME": f"{root}_{suffix}{ext}"}
+
+        start_method = multiprocessing.get_start_method()
+        if start_method == "fork":
+            return orig_settings_dict
+        if start_method == "spawn":
+            return {
+                **orig_settings_dict,
+                "NAME": f"{self.connection.alias}_{suffix}.sqlite3",
+            }
+        raise NotSupportedError(
+            f"Cloning with start method {start_method!r} is not supported."
+        )
+
+    def _clone_test_db(self, suffix, verbosity, keepdb=False):
+        source_database_name = self.connection.settings_dict["NAME"]
+        target_database_name = self.get_test_db_clone_settings(suffix)["NAME"]
+        if not self.is_in_memory_db(source_database_name):
+            # Erase the old test database
+            if os.access(target_database_name, os.F_OK):
+                if keepdb:
+                    return
+                if verbosity >= 1:
+                    self.log(
+                        "Destroying old test database for alias %s..."
+                        % (
+                            self._get_database_display_str(
+                                verbosity, target_database_name
+                            ),
+                        )
+                    )
+                try:
+                    os.remove(target_database_name)
+                except Exception as e:
+                    self.log("Got an error deleting the old test database: %s" % e)
+                    sys.exit(2)
+            try:
+                shutil.copy(source_database_name, target_database_name)
+            except Exception as e:
+                self.log("Got an error cloning the test database: %s" % e)
+                sys.exit(2)
+        # Forking automatically makes a copy of an in-memory database.
+        # Spawn requires migrating to disk which will be re-opened in
+        # setup_worker_connection.
+        elif multiprocessing.get_start_method() == "spawn":
+            ondisk_db = sqlite3.connect(target_database_name, uri=True)
+            self.connection.connection.backup(ondisk_db)
+
+    def _destroy_test_db(self, test_database_name, verbosity):
+        if test_database_name and not self.is_in_memory_db(test_database_name):
+            # Remove the SQLite database file
+            os.remove(test_database_name)
+
+    def test_db_signature(self):
+        """
+        Return a tuple that uniquely identifies a test database.
+
+        This takes into account the special cases of ":memory:" and "" for
+        SQLite since the databases will be distinct despite having the same
+        TEST NAME. See https://www.sqlite.org/inmemorydb.html
+        """
+        test_database_name = self._get_test_db_name()
+        sig = [self.connection.settings_dict["NAME"]]
+        if self.is_in_memory_db(test_database_name):
+            sig.append(self.connection.alias)
+        else:
+            sig.append(test_database_name)
+        return tuple(sig)
+
+    def setup_worker_connection(self, _worker_id):
+        settings_dict = self.get_test_db_clone_settings(_worker_id)
+        # connection.settings_dict must be updated in place for changes to be
+        # reflected in django.db.connections. Otherwise new threads would
+        # connect to the default database instead of the appropriate clone.
+        start_method = multiprocessing.get_start_method()
+        if start_method == "fork":
+            # Update settings_dict in place.
+            self.connection.settings_dict.update(settings_dict)
+            self.connection.close()
+        elif start_method == "spawn":
+            alias = self.connection.alias
+            connection_str = (
+                f"file:memorydb_{alias}_{_worker_id}?mode=memory&cache=shared"
+            )
+            source_db = self.connection.Database.connect(
+                f"file:{alias}_{_worker_id}.sqlite3", uri=True
+            )
+            target_db = sqlite3.connect(connection_str, uri=True)
+            source_db.backup(target_db)
+            source_db.close()
+            # Update settings_dict in place.
+            self.connection.settings_dict.update(settings_dict)
+            self.connection.settings_dict["NAME"] = connection_str
+            # Re-open connection to in-memory database before closing copy
+            # connection.
+            self.connection.connect()
+            target_db.close()
+            if os.environ.get("RUNNING_DJANGOS_TEST_SUITE") == "true":
+                self.mark_expected_failures_and_skips()

env/lib/python3.8/site-packages/django/db/backends/sqlite3/features.py

@@ -0,0 +1,141 @@
+import operator
+
+from django.db import transaction
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.utils import OperationalError
+from django.utils.functional import cached_property
+
+from .base import Database
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    minimum_database_version = (3, 9)
+    test_db_allows_multiple_connections = False
+    supports_unspecified_pk = True
+    supports_timezones = False
+    max_query_params = 999
+    supports_transactions = True
+    atomic_transactions = False
+    can_rollback_ddl = True
+    can_create_inline_fk = False
+    supports_paramstyle_pyformat = False
+    requires_literal_defaults = True
+    can_clone_databases = True
+    supports_temporal_subtraction = True
+    ignores_table_name_case = True
+    supports_cast_with_precision = False
+    time_cast_precision = 3
+    can_release_savepoints = True
+    has_case_insensitive_like = True
+    # Is "ALTER TABLE ... RENAME COLUMN" supported?
+    can_alter_table_rename_column = Database.sqlite_version_info >= (3, 25, 0)
+    # Is "ALTER TABLE ... DROP COLUMN" supported?
+    can_alter_table_drop_column = Database.sqlite_version_info >= (3, 35, 5)
+    supports_parentheses_in_compound = False
+    # Deferred constraint checks can be emulated on SQLite < 3.20 but not in a
+    # reasonably performant way.
+    supports_pragma_foreign_key_check = Database.sqlite_version_info >= (3, 20, 0)
+    can_defer_constraint_checks = supports_pragma_foreign_key_check
+    supports_functions_in_partial_indexes = Database.sqlite_version_info >= (3, 15, 0)
+    supports_over_clause = Database.sqlite_version_info >= (3, 25, 0)
+    supports_frame_range_fixed_distance = Database.sqlite_version_info >= (3, 28, 0)
+    supports_aggregate_filter_clause = Database.sqlite_version_info >= (3, 30, 1)
+    supports_order_by_nulls_modifier = Database.sqlite_version_info >= (3, 30, 0)
+    order_by_nulls_first = True
+    supports_json_field_contains = False
+    supports_update_conflicts = Database.sqlite_version_info >= (3, 24, 0)
+    supports_update_conflicts_with_target = supports_update_conflicts
+    test_collations = {
+        "ci": "nocase",
+        "cs": "binary",
+        "non_default": "nocase",
+    }
+    django_test_expected_failures = {
+        # The django_format_dtdelta() function doesn't properly handle mixed
+        # Date/DateTime fields and timedeltas.
+        "expressions.tests.FTimeDeltaTests.test_mixed_comparisons1",
+    }
+
+    @cached_property
+    def django_test_skips(self):
+        skips = {
+            "SQLite stores values rounded to 15 significant digits.": {
+                "model_fields.test_decimalfield.DecimalFieldTests."
+                "test_fetch_from_db_without_float_rounding",
+            },
+            "SQLite naively remakes the table on field alteration.": {
+                "schema.tests.SchemaTests.test_unique_no_unnecessary_fk_drops",
+                "schema.tests.SchemaTests.test_unique_and_reverse_m2m",
+                "schema.tests.SchemaTests."
+                "test_alter_field_default_doesnt_perform_queries",
+                "schema.tests.SchemaTests."
+                "test_rename_column_renames_deferred_sql_references",
+            },
+            "SQLite doesn't support negative precision for ROUND().": {
+                "db_functions.math.test_round.RoundTests."
+                "test_null_with_negative_precision",
+                "db_functions.math.test_round.RoundTests."
+                "test_decimal_with_negative_precision",
+                "db_functions.math.test_round.RoundTests."
+                "test_float_with_negative_precision",
+                "db_functions.math.test_round.RoundTests."
+                "test_integer_with_negative_precision",
+            },
+        }
+        if Database.sqlite_version_info < (3, 27):
+            skips.update(
+                {
+                    "Nondeterministic failure on SQLite < 3.27.": {
+                        "expressions_window.tests.WindowFunctionTests."
+                        "test_subquery_row_range_rank",
+                    },
+                }
+            )
+        if self.connection.is_in_memory_db():
+            skips.update(
+                {
+                    "the sqlite backend's close() method is a no-op when using an "
+                    "in-memory database": {
+                        "servers.test_liveserverthread.LiveServerThreadTest."
+                        "test_closes_connections",
+                        "servers.tests.LiveServerTestCloseConnectionTest."
+                        "test_closes_connections",
+                    },
+                }
+            )
+        return skips
+
+    @cached_property
+    def supports_atomic_references_rename(self):
+        return Database.sqlite_version_info >= (3, 26, 0)
+
+    @cached_property
+    def introspected_field_types(self):
+        return {
+            **super().introspected_field_types,
+            "BigAutoField": "AutoField",
+            "DurationField": "BigIntegerField",
+            "GenericIPAddressField": "CharField",
+            "SmallAutoField": "AutoField",
+        }
+
+    @cached_property
+    def supports_json_field(self):
+        with self.connection.cursor() as cursor:
+            try:
+                with transaction.atomic(self.connection.alias):
+                    cursor.execute('SELECT JSON(\'{"a": "b"}\')')
+            except OperationalError:
+                return False
+        return True
+
+    can_introspect_json_field = property(operator.attrgetter("supports_json_field"))
+    has_json_object_function = property(operator.attrgetter("supports_json_field"))
+
+    @cached_property
+    def can_return_columns_from_insert(self):
+        return Database.sqlite_version_info >= (3, 35)
+
+    can_return_rows_from_bulk_insert = property(
+        operator.attrgetter("can_return_columns_from_insert")
+    )

env/lib/python3.8/site-packages/django/db/backends/sqlite3/introspection.py

@@ -0,0 +1,438 @@
+from collections import namedtuple
+
+import sqlparse
+
+from django.db import DatabaseError
+from django.db.backends.base.introspection import BaseDatabaseIntrospection
+from django.db.backends.base.introspection import FieldInfo as BaseFieldInfo
+from django.db.backends.base.introspection import TableInfo
+from django.db.models import Index
+from django.utils.regex_helper import _lazy_re_compile
+
+FieldInfo = namedtuple(
+    "FieldInfo", BaseFieldInfo._fields + ("pk", "has_json_constraint")
+)
+
+field_size_re = _lazy_re_compile(r"^\s*(?:var)?char\s*\(\s*(\d+)\s*\)\s*$")
+
+
+def get_field_size(name):
+    """Extract the size number from a "varchar(11)" type name"""
+    m = field_size_re.search(name)
+    return int(m[1]) if m else None
+
+
+# This light wrapper "fakes" a dictionary interface, because some SQLite data
+# types include variables in them -- e.g. "varchar(30)" -- and can't be matched
+# as a simple dictionary lookup.
+class FlexibleFieldLookupDict:
+    # Maps SQL types to Django Field types. Some of the SQL types have multiple
+    # entries here because SQLite allows for anything and doesn't normalize the
+    # field type; it uses whatever was given.
+    base_data_types_reverse = {
+        "bool": "BooleanField",
+        "boolean": "BooleanField",
+        "smallint": "SmallIntegerField",
+        "smallint unsigned": "PositiveSmallIntegerField",
+        "smallinteger": "SmallIntegerField",
+        "int": "IntegerField",
+        "integer": "IntegerField",
+        "bigint": "BigIntegerField",
+        "integer unsigned": "PositiveIntegerField",
+        "bigint unsigned": "PositiveBigIntegerField",
+        "decimal": "DecimalField",
+        "real": "FloatField",
+        "text": "TextField",
+        "char": "CharField",
+        "varchar": "CharField",
+        "blob": "BinaryField",
+        "date": "DateField",
+        "datetime": "DateTimeField",
+        "time": "TimeField",
+    }
+
+    def __getitem__(self, key):
+        key = key.lower().split("(", 1)[0].strip()
+        return self.base_data_types_reverse[key]
+
+
+class DatabaseIntrospection(BaseDatabaseIntrospection):
+    data_types_reverse = FlexibleFieldLookupDict()
+
+    def get_field_type(self, data_type, description):
+        field_type = super().get_field_type(data_type, description)
+        if description.pk and field_type in {
+            "BigIntegerField",
+            "IntegerField",
+            "SmallIntegerField",
+        }:
+            # No support for BigAutoField or SmallAutoField as SQLite treats
+            # all integer primary keys as signed 64-bit integers.
+            return "AutoField"
+        if description.has_json_constraint:
+            return "JSONField"
+        return field_type
+
+    def get_table_list(self, cursor):
+        """Return a list of table and view names in the current database."""
+        # Skip the sqlite_sequence system table used for autoincrement key
+        # generation.
+        cursor.execute(
+            """
+            SELECT name, type FROM sqlite_master
+            WHERE type in ('table', 'view') AND NOT name='sqlite_sequence'
+            ORDER BY name"""
+        )
+        return [TableInfo(row[0], row[1][0]) for row in cursor.fetchall()]
+
+    def get_table_description(self, cursor, table_name):
+        """
+        Return a description of the table with the DB-API cursor.description
+        interface.
+        """
+        cursor.execute(
+            "PRAGMA table_info(%s)" % self.connection.ops.quote_name(table_name)
+        )
+        table_info = cursor.fetchall()
+        if not table_info:
+            raise DatabaseError(f"Table {table_name} does not exist (empty pragma).")
+        collations = self._get_column_collations(cursor, table_name)
+        json_columns = set()
+        if self.connection.features.can_introspect_json_field:
+            for line in table_info:
+                column = line[1]
+                json_constraint_sql = '%%json_valid("%s")%%' % column
+                has_json_constraint = cursor.execute(
+                    """
+                    SELECT sql
+                    FROM sqlite_master
+                    WHERE
+                        type = 'table' AND
+                        name = %s AND
+                        sql LIKE %s
+                """,
+                    [table_name, json_constraint_sql],
+                ).fetchone()
+                if has_json_constraint:
+                    json_columns.add(column)
+        return [
+            FieldInfo(
+                name,
+                data_type,
+                None,
+                get_field_size(data_type),
+                None,
+                None,
+                not notnull,
+                default,
+                collations.get(name),
+                pk == 1,
+                name in json_columns,
+            )
+            for cid, name, data_type, notnull, default, pk in table_info
+        ]
+
+    def get_sequences(self, cursor, table_name, table_fields=()):
+        pk_col = self.get_primary_key_column(cursor, table_name)
+        return [{"table": table_name, "column": pk_col}]
+
+    def get_relations(self, cursor, table_name):
+        """
+        Return a dictionary of {column_name: (ref_column_name, ref_table_name)}
+        representing all foreign keys in the given table.
+        """
+        cursor.execute(
+            "PRAGMA foreign_key_list(%s)" % self.connection.ops.quote_name(table_name)
+        )
+        return {
+            column_name: (ref_column_name, ref_table_name)
+            for (
+                _,
+                _,
+                ref_table_name,
+                column_name,
+                ref_column_name,
+                *_,
+            ) in cursor.fetchall()
+        }
+
+    def get_primary_key_column(self, cursor, table_name):
+        """Return the column name of the primary key for the given table."""
+        cursor.execute(
+            "PRAGMA table_info(%s)" % self.connection.ops.quote_name(table_name)
+        )
+        for _, name, *_, pk in cursor.fetchall():
+            if pk:
+                return name
+        return None
+
+    def _parse_column_or_constraint_definition(self, tokens, columns):
+        token = None
+        is_constraint_definition = None
+        field_name = None
+        constraint_name = None
+        unique = False
+        unique_columns = []
+        check = False
+        check_columns = []
+        braces_deep = 0
+        for token in tokens:
+            if token.match(sqlparse.tokens.Punctuation, "("):
+                braces_deep += 1
+            elif token.match(sqlparse.tokens.Punctuation, ")"):
+                braces_deep -= 1
+                if braces_deep < 0:
+                    # End of columns and constraints for table definition.
+                    break
+            elif braces_deep == 0 and token.match(sqlparse.tokens.Punctuation, ","):
+                # End of current column or constraint definition.
+                break
+            # Detect column or constraint definition by first token.
+            if is_constraint_definition is None:
+                is_constraint_definition = token.match(
+                    sqlparse.tokens.Keyword, "CONSTRAINT"
+                )
+                if is_constraint_definition:
+                    continue
+            if is_constraint_definition:
+                # Detect constraint name by second token.
+                if constraint_name is None:
+                    if token.ttype in (sqlparse.tokens.Name, sqlparse.tokens.Keyword):
+                        constraint_name = token.value
+                    elif token.ttype == sqlparse.tokens.Literal.String.Symbol:
+                        constraint_name = token.value[1:-1]
+                # Start constraint columns parsing after UNIQUE keyword.
+                if token.match(sqlparse.tokens.Keyword, "UNIQUE"):
+                    unique = True
+                    unique_braces_deep = braces_deep
+                elif unique:
+                    if unique_braces_deep == braces_deep:
+                        if unique_columns:
+                            # Stop constraint parsing.
+                            unique = False
+                        continue
+                    if token.ttype in (sqlparse.tokens.Name, sqlparse.tokens.Keyword):
+                        unique_columns.append(token.value)
+                    elif token.ttype == sqlparse.tokens.Literal.String.Symbol:
+                        unique_columns.append(token.value[1:-1])
+            else:
+                # Detect field name by first token.
+                if field_name is None:
+                    if token.ttype in (sqlparse.tokens.Name, sqlparse.tokens.Keyword):
+                        field_name = token.value
+                    elif token.ttype == sqlparse.tokens.Literal.String.Symbol:
+                        field_name = token.value[1:-1]
+                if token.match(sqlparse.tokens.Keyword, "UNIQUE"):
+                    unique_columns = [field_name]
+            # Start constraint columns parsing after CHECK keyword.
+            if token.match(sqlparse.tokens.Keyword, "CHECK"):
+                check = True
+                check_braces_deep = braces_deep
+            elif check:
+                if check_braces_deep == braces_deep:
+                    if check_columns:
+                        # Stop constraint parsing.
+                        check = False
+                    continue
+                if token.ttype in (sqlparse.tokens.Name, sqlparse.tokens.Keyword):
+                    if token.value in columns:
+                        check_columns.append(token.value)
+                elif token.ttype == sqlparse.tokens.Literal.String.Symbol:
+                    if token.value[1:-1] in columns:
+                        check_columns.append(token.value[1:-1])
+        unique_constraint = (
+            {
+                "unique": True,
+                "columns": unique_columns,
+                "primary_key": False,
+                "foreign_key": None,
+                "check": False,
+                "index": False,
+            }
+            if unique_columns
+            else None
+        )
+        check_constraint = (
+            {
+                "check": True,
+                "columns": check_columns,
+                "primary_key": False,
+                "unique": False,
+                "foreign_key": None,
+                "index": False,
+            }
+            if check_columns
+            else None
+        )
+        return constraint_name, unique_constraint, check_constraint, token
+
+    def _parse_table_constraints(self, sql, columns):
+        # Check constraint parsing is based of SQLite syntax diagram.
+        # https://www.sqlite.org/syntaxdiagrams.html#table-constraint
+        statement = sqlparse.parse(sql)[0]
+        constraints = {}
+        unnamed_constrains_index = 0
+        tokens = (token for token in statement.flatten() if not token.is_whitespace)
+        # Go to columns and constraint definition
+        for token in tokens:
+            if token.match(sqlparse.tokens.Punctuation, "("):
+                break
+        # Parse columns and constraint definition
+        while True:
+            (
+                constraint_name,
+                unique,
+                check,
+                end_token,
+            ) = self._parse_column_or_constraint_definition(tokens, columns)
+            if unique:
+                if constraint_name:
+                    constraints[constraint_name] = unique
+                else:
+                    unnamed_constrains_index += 1
+                    constraints[
+                        "__unnamed_constraint_%s__" % unnamed_constrains_index
+                    ] = unique
+            if check:
+                if constraint_name:
+                    constraints[constraint_name] = check
+                else:
+                    unnamed_constrains_index += 1
+                    constraints[
+                        "__unnamed_constraint_%s__" % unnamed_constrains_index
+                    ] = check
+            if end_token.match(sqlparse.tokens.Punctuation, ")"):
+                break
+        return constraints
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieve any constraints or keys (unique, pk, fk, check, index) across
+        one or more columns.
+        """
+        constraints = {}
+        # Find inline check constraints.
+        try:
+            table_schema = cursor.execute(
+                "SELECT sql FROM sqlite_master WHERE type='table' and name=%s"
+                % (self.connection.ops.quote_name(table_name),)
+            ).fetchone()[0]
+        except TypeError:
+            # table_name is a view.
+            pass
+        else:
+            columns = {
+                info.name for info in self.get_table_description(cursor, table_name)
+            }
+            constraints.update(self._parse_table_constraints(table_schema, columns))
+
+        # Get the index info
+        cursor.execute(
+            "PRAGMA index_list(%s)" % self.connection.ops.quote_name(table_name)
+        )
+        for row in cursor.fetchall():
+            # SQLite 3.8.9+ has 5 columns, however older versions only give 3
+            # columns. Discard last 2 columns if there.
+            number, index, unique = row[:3]
+            cursor.execute(
+                "SELECT sql FROM sqlite_master "
+                "WHERE type='index' AND name=%s" % self.connection.ops.quote_name(index)
+            )
+            # There's at most one row.
+            (sql,) = cursor.fetchone() or (None,)
+            # Inline constraints are already detected in
+            # _parse_table_constraints(). The reasons to avoid fetching inline
+            # constraints from `PRAGMA index_list` are:
+            # - Inline constraints can have a different name and information
+            #   than what `PRAGMA index_list` gives.
+            # - Not all inline constraints may appear in `PRAGMA index_list`.
+            if not sql:
+                # An inline constraint
+                continue
+            # Get the index info for that index
+            cursor.execute(
+                "PRAGMA index_info(%s)" % self.connection.ops.quote_name(index)
+            )
+            for index_rank, column_rank, column in cursor.fetchall():
+                if index not in constraints:
+                    constraints[index] = {
+                        "columns": [],
+                        "primary_key": False,
+                        "unique": bool(unique),
+                        "foreign_key": None,
+                        "check": False,
+                        "index": True,
+                    }
+                constraints[index]["columns"].append(column)
+            # Add type and column orders for indexes
+            if constraints[index]["index"]:
+                # SQLite doesn't support any index type other than b-tree
+                constraints[index]["type"] = Index.suffix
+                orders = self._get_index_columns_orders(sql)
+                if orders is not None:
+                    constraints[index]["orders"] = orders
+        # Get the PK
+        pk_column = self.get_primary_key_column(cursor, table_name)
+        if pk_column:
+            # SQLite doesn't actually give a name to the PK constraint,
+            # so we invent one. This is fine, as the SQLite backend never
+            # deletes PK constraints by name, as you can't delete constraints
+            # in SQLite; we remake the table with a new PK instead.
+            constraints["__primary__"] = {
+                "columns": [pk_column],
+                "primary_key": True,
+                "unique": False,  # It's not actually a unique constraint.
+                "foreign_key": None,
+                "check": False,
+                "index": False,
+            }
+        relations = enumerate(self.get_relations(cursor, table_name).items())
+        constraints.update(
+            {
+                f"fk_{index}": {
+                    "columns": [column_name],
+                    "primary_key": False,
+                    "unique": False,
+                    "foreign_key": (ref_table_name, ref_column_name),
+                    "check": False,
+                    "index": False,
+                }
+                for index, (column_name, (ref_column_name, ref_table_name)) in relations
+            }
+        )
+        return constraints
+
+    def _get_index_columns_orders(self, sql):
+        tokens = sqlparse.parse(sql)[0]
+        for token in tokens:
+            if isinstance(token, sqlparse.sql.Parenthesis):
+                columns = str(token).strip("()").split(", ")
+                return ["DESC" if info.endswith("DESC") else "ASC" for info in columns]
+        return None
+
+    def _get_column_collations(self, cursor, table_name):
+        row = cursor.execute(
+            """
+            SELECT sql
+            FROM sqlite_master
+            WHERE type = 'table' AND name = %s
+        """,
+            [table_name],
+        ).fetchone()
+        if not row:
+            return {}
+
+        sql = row[0]
+        columns = str(sqlparse.parse(sql)[0][-1]).strip("()").split(", ")
+        collations = {}
+        for column in columns:
+            tokens = column[1:].split()
+            column_name = tokens[0].strip('"')
+            for index, token in enumerate(tokens):
+                if token == "COLLATE":
+                    collation = tokens[index + 1]
+                    break
+            else:
+                collation = None
+            collations[column_name] = collation
+        return collations

env/lib/python3.8/site-packages/django/db/backends/sqlite3/operations.py

@@ -0,0 +1,436 @@
+import datetime
+import decimal
+import uuid
+from functools import lru_cache
+from itertools import chain
+
+from django.conf import settings
+from django.core.exceptions import FieldError
+from django.db import DatabaseError, NotSupportedError, models
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.models.constants import OnConflict
+from django.db.models.expressions import Col
+from django.utils import timezone
+from django.utils.dateparse import parse_date, parse_datetime, parse_time
+from django.utils.functional import cached_property
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    cast_char_field_without_max_length = "text"
+    cast_data_types = {
+        "DateField": "TEXT",
+        "DateTimeField": "TEXT",
+    }
+    explain_prefix = "EXPLAIN QUERY PLAN"
+    # List of datatypes to that cannot be extracted with JSON_EXTRACT() on
+    # SQLite. Use JSON_TYPE() instead.
+    jsonfield_datatype_values = frozenset(["null", "false", "true"])
+
+    def bulk_batch_size(self, fields, objs):
+        """
+        SQLite has a compile-time default (SQLITE_LIMIT_VARIABLE_NUMBER) of
+        999 variables per query.
+
+        If there's only a single field to insert, the limit is 500
+        (SQLITE_MAX_COMPOUND_SELECT).
+        """
+        if len(fields) == 1:
+            return 500
+        elif len(fields) > 1:
+            return self.connection.features.max_query_params // len(fields)
+        else:
+            return len(objs)
+
+    def check_expression_support(self, expression):
+        bad_fields = (models.DateField, models.DateTimeField, models.TimeField)
+        bad_aggregates = (models.Sum, models.Avg, models.Variance, models.StdDev)
+        if isinstance(expression, bad_aggregates):
+            for expr in expression.get_source_expressions():
+                try:
+                    output_field = expr.output_field
+                except (AttributeError, FieldError):
+                    # Not every subexpression has an output_field which is fine
+                    # to ignore.
+                    pass
+                else:
+                    if isinstance(output_field, bad_fields):
+                        raise NotSupportedError(
+                            "You cannot use Sum, Avg, StdDev, and Variance "
+                            "aggregations on date/time fields in sqlite3 "
+                            "since date/time is saved as text."
+                        )
+        if (
+            isinstance(expression, models.Aggregate)
+            and expression.distinct
+            and len(expression.source_expressions) > 1
+        ):
+            raise NotSupportedError(
+                "SQLite doesn't support DISTINCT on aggregate functions "
+                "accepting multiple arguments."
+            )
+
+    def date_extract_sql(self, lookup_type, sql, params):
+        """
+        Support EXTRACT with a user-defined function django_date_extract()
+        that's registered in connect(). Use single quotes because this is a
+        string and could otherwise cause a collision with a field name.
+        """
+        return f"django_date_extract(%s, {sql})", (lookup_type.lower(), *params)
+
+    def fetch_returned_insert_rows(self, cursor):
+        """
+        Given a cursor object that has just performed an INSERT...RETURNING
+        statement into a table, return the list of returned data.
+        """
+        return cursor.fetchall()
+
+    def format_for_duration_arithmetic(self, sql):
+        """Do nothing since formatting is handled in the custom function."""
+        return sql
+
+    def date_trunc_sql(self, lookup_type, sql, params, tzname=None):
+        return f"django_date_trunc(%s, {sql}, %s, %s)", (
+            lookup_type.lower(),
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def time_trunc_sql(self, lookup_type, sql, params, tzname=None):
+        return f"django_time_trunc(%s, {sql}, %s, %s)", (
+            lookup_type.lower(),
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def _convert_tznames_to_sql(self, tzname):
+        if tzname and settings.USE_TZ:
+            return tzname, self.connection.timezone_name
+        return None, None
+
+    def datetime_cast_date_sql(self, sql, params, tzname):
+        return f"django_datetime_cast_date({sql}, %s, %s)", (
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def datetime_cast_time_sql(self, sql, params, tzname):
+        return f"django_datetime_cast_time({sql}, %s, %s)", (
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def datetime_extract_sql(self, lookup_type, sql, params, tzname):
+        return f"django_datetime_extract(%s, {sql}, %s, %s)", (
+            lookup_type.lower(),
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def datetime_trunc_sql(self, lookup_type, sql, params, tzname):
+        return f"django_datetime_trunc(%s, {sql}, %s, %s)", (
+            lookup_type.lower(),
+            *params,
+            *self._convert_tznames_to_sql(tzname),
+        )
+
+    def time_extract_sql(self, lookup_type, sql, params):
+        return f"django_time_extract(%s, {sql})", (lookup_type.lower(), *params)
+
+    def pk_default_value(self):
+        return "NULL"
+
+    def _quote_params_for_last_executed_query(self, params):
+        """
+        Only for last_executed_query! Don't use this to execute SQL queries!
+        """
+        # This function is limited both by SQLITE_LIMIT_VARIABLE_NUMBER (the
+        # number of parameters, default = 999) and SQLITE_MAX_COLUMN (the
+        # number of return values, default = 2000). Since Python's sqlite3
+        # module doesn't expose the get_limit() C API, assume the default
+        # limits are in effect and split the work in batches if needed.
+        BATCH_SIZE = 999
+        if len(params) > BATCH_SIZE:
+            results = ()
+            for index in range(0, len(params), BATCH_SIZE):
+                chunk = params[index : index + BATCH_SIZE]
+                results += self._quote_params_for_last_executed_query(chunk)
+            return results
+
+        sql = "SELECT " + ", ".join(["QUOTE(?)"] * len(params))
+        # Bypass Django's wrappers and use the underlying sqlite3 connection
+        # to avoid logging this query - it would trigger infinite recursion.
+        cursor = self.connection.connection.cursor()
+        # Native sqlite3 cursors cannot be used as context managers.
+        try:
+            return cursor.execute(sql, params).fetchone()
+        finally:
+            cursor.close()
+
+    def last_executed_query(self, cursor, sql, params):
+        # Python substitutes parameters in Modules/_sqlite/cursor.c with:
+        # pysqlite_statement_bind_parameters(
+        #   self->statement, parameters, allow_8bit_chars
+        # );
+        # Unfortunately there is no way to reach self->statement from Python,
+        # so we quote and substitute parameters manually.
+        if params:
+            if isinstance(params, (list, tuple)):
+                params = self._quote_params_for_last_executed_query(params)
+            else:
+                values = tuple(params.values())
+                values = self._quote_params_for_last_executed_query(values)
+                params = dict(zip(params, values))
+            return sql % params
+        # For consistency with SQLiteCursorWrapper.execute(), just return sql
+        # when there are no parameters. See #13648 and #17158.
+        else:
+            return sql
+
+    def quote_name(self, name):
+        if name.startswith('"') and name.endswith('"'):
+            return name  # Quoting once is enough.
+        return '"%s"' % name
+
+    def no_limit_value(self):
+        return -1
+
+    def __references_graph(self, table_name):
+        query = """
+        WITH tables AS (
+            SELECT %s name
+            UNION
+            SELECT sqlite_master.name
+            FROM sqlite_master
+            JOIN tables ON (sql REGEXP %s || tables.name || %s)
+        ) SELECT name FROM tables;
+        """
+        params = (
+            table_name,
+            r'(?i)\s+references\s+("|\')?',
+            r'("|\')?\s*\(',
+        )
+        with self.connection.cursor() as cursor:
+            results = cursor.execute(query, params)
+            return [row[0] for row in results.fetchall()]
+
+    @cached_property
+    def _references_graph(self):
+        # 512 is large enough to fit the ~330 tables (as of this writing) in
+        # Django's test suite.
+        return lru_cache(maxsize=512)(self.__references_graph)
+
+    def sql_flush(self, style, tables, *, reset_sequences=False, allow_cascade=False):
+        if tables and allow_cascade:
+            # Simulate TRUNCATE CASCADE by recursively collecting the tables
+            # referencing the tables to be flushed.
+            tables = set(
+                chain.from_iterable(self._references_graph(table) for table in tables)
+            )
+        sql = [
+            "%s %s %s;"
+            % (
+                style.SQL_KEYWORD("DELETE"),
+                style.SQL_KEYWORD("FROM"),
+                style.SQL_FIELD(self.quote_name(table)),
+            )
+            for table in tables
+        ]
+        if reset_sequences:
+            sequences = [{"table": table} for table in tables]
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+        return sql
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        if not sequences:
+            return []
+        return [
+            "%s %s %s %s = 0 %s %s %s (%s);"
+            % (
+                style.SQL_KEYWORD("UPDATE"),
+                style.SQL_TABLE(self.quote_name("sqlite_sequence")),
+                style.SQL_KEYWORD("SET"),
+                style.SQL_FIELD(self.quote_name("seq")),
+                style.SQL_KEYWORD("WHERE"),
+                style.SQL_FIELD(self.quote_name("name")),
+                style.SQL_KEYWORD("IN"),
+                ", ".join(
+                    ["'%s'" % sequence_info["table"] for sequence_info in sequences]
+                ),
+            ),
+        ]
+
+    def adapt_datetimefield_value(self, value):
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, "resolve_expression"):
+            return value
+
+        # SQLite doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = timezone.make_naive(value, self.connection.timezone)
+            else:
+                raise ValueError(
+                    "SQLite backend does not support timezone-aware datetimes when "
+                    "USE_TZ is False."
+                )
+
+        return str(value)
+
+    def adapt_timefield_value(self, value):
+        if value is None:
+            return None
+
+        # Expression values are adapted by the database.
+        if hasattr(value, "resolve_expression"):
+            return value
+
+        # SQLite doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            raise ValueError("SQLite backend does not support timezone-aware times.")
+
+        return str(value)
+
+    def get_db_converters(self, expression):
+        converters = super().get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type == "DateTimeField":
+            converters.append(self.convert_datetimefield_value)
+        elif internal_type == "DateField":
+            converters.append(self.convert_datefield_value)
+        elif internal_type == "TimeField":
+            converters.append(self.convert_timefield_value)
+        elif internal_type == "DecimalField":
+            converters.append(self.get_decimalfield_converter(expression))
+        elif internal_type == "UUIDField":
+            converters.append(self.convert_uuidfield_value)
+        elif internal_type == "BooleanField":
+            converters.append(self.convert_booleanfield_value)
+        return converters
+
+    def convert_datetimefield_value(self, value, expression, connection):
+        if value is not None:
+            if not isinstance(value, datetime.datetime):
+                value = parse_datetime(value)
+            if settings.USE_TZ and not timezone.is_aware(value):
+                value = timezone.make_aware(value, self.connection.timezone)
+        return value
+
+    def convert_datefield_value(self, value, expression, connection):
+        if value is not None:
+            if not isinstance(value, datetime.date):
+                value = parse_date(value)
+        return value
+
+    def convert_timefield_value(self, value, expression, connection):
+        if value is not None:
+            if not isinstance(value, datetime.time):
+                value = parse_time(value)
+        return value
+
+    def get_decimalfield_converter(self, expression):
+        # SQLite stores only 15 significant digits. Digits coming from
+        # float inaccuracy must be removed.
+        create_decimal = decimal.Context(prec=15).create_decimal_from_float
+        if isinstance(expression, Col):
+            quantize_value = decimal.Decimal(1).scaleb(
+                -expression.output_field.decimal_places
+            )
+
+            def converter(value, expression, connection):
+                if value is not None:
+                    return create_decimal(value).quantize(
+                        quantize_value, context=expression.output_field.context
+                    )
+
+        else:
+
+            def converter(value, expression, connection):
+                if value is not None:
+                    return create_decimal(value)
+
+        return converter
+
+    def convert_uuidfield_value(self, value, expression, connection):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    def convert_booleanfield_value(self, value, expression, connection):
+        return bool(value) if value in (1, 0) else value
+
+    def bulk_insert_sql(self, fields, placeholder_rows):
+        placeholder_rows_sql = (", ".join(row) for row in placeholder_rows)
+        values_sql = ", ".join(f"({sql})" for sql in placeholder_rows_sql)
+        return f"VALUES {values_sql}"
+
+    def combine_expression(self, connector, sub_expressions):
+        # SQLite doesn't have a ^ operator, so use the user-defined POWER
+        # function that's registered in connect().
+        if connector == "^":
+            return "POWER(%s)" % ",".join(sub_expressions)
+        elif connector == "#":
+            return "BITXOR(%s)" % ",".join(sub_expressions)
+        return super().combine_expression(connector, sub_expressions)
+
+    def combine_duration_expression(self, connector, sub_expressions):
+        if connector not in ["+", "-", "*", "/"]:
+            raise DatabaseError("Invalid connector for timedelta: %s." % connector)
+        fn_params = ["'%s'" % connector] + sub_expressions
+        if len(fn_params) > 3:
+            raise ValueError("Too many params for timedelta operations.")
+        return "django_format_dtdelta(%s)" % ", ".join(fn_params)
+
+    def integer_field_range(self, internal_type):
+        # SQLite doesn't enforce any integer constraints
+        return (None, None)
+
+    def subtract_temporals(self, internal_type, lhs, rhs):
+        lhs_sql, lhs_params = lhs
+        rhs_sql, rhs_params = rhs
+        params = (*lhs_params, *rhs_params)
+        if internal_type == "TimeField":
+            return "django_time_diff(%s, %s)" % (lhs_sql, rhs_sql), params
+        return "django_timestamp_diff(%s, %s)" % (lhs_sql, rhs_sql), params
+
+    def insert_statement(self, on_conflict=None):
+        if on_conflict == OnConflict.IGNORE:
+            return "INSERT OR IGNORE INTO"
+        return super().insert_statement(on_conflict=on_conflict)
+
+    def return_insert_columns(self, fields):
+        # SQLite < 3.35 doesn't support an INSERT...RETURNING statement.
+        if not fields:
+            return "", ()
+        columns = [
+            "%s.%s"
+            % (
+                self.quote_name(field.model._meta.db_table),
+                self.quote_name(field.column),
+            )
+            for field in fields
+        ]
+        return "RETURNING %s" % ", ".join(columns), ()
+
+    def on_conflict_suffix_sql(self, fields, on_conflict, update_fields, unique_fields):
+        if (
+            on_conflict == OnConflict.UPDATE
+            and self.connection.features.supports_update_conflicts_with_target
+        ):
+            return "ON CONFLICT(%s) DO UPDATE SET %s" % (
+                ", ".join(map(self.quote_name, unique_fields)),
+                ", ".join(
+                    [
+                        f"{field} = EXCLUDED.{field}"
+                        for field in map(self.quote_name, update_fields)
+                    ]
+                ),
+            )
+        return super().on_conflict_suffix_sql(
+            fields,
+            on_conflict,
+            update_fields,
+            unique_fields,
+        )

env/lib/python3.8/site-packages/django/db/backends/sqlite3/schema.py

@@ -0,0 +1,559 @@
+import copy
+from decimal import Decimal
+
+from django.apps.registry import Apps
+from django.db import NotSupportedError
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.backends.ddl_references import Statement
+from django.db.backends.utils import strip_quotes
+from django.db.models import UniqueConstraint
+from django.db.transaction import atomic
+
+
+class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
+
+    sql_delete_table = "DROP TABLE %(table)s"
+    sql_create_fk = None
+    sql_create_inline_fk = (
+        "REFERENCES %(to_table)s (%(to_column)s) DEFERRABLE INITIALLY DEFERRED"
+    )
+    sql_create_column_inline_fk = sql_create_inline_fk
+    sql_delete_column = "ALTER TABLE %(table)s DROP COLUMN %(column)s"
+    sql_create_unique = "CREATE UNIQUE INDEX %(name)s ON %(table)s (%(columns)s)"
+    sql_delete_unique = "DROP INDEX %(name)s"
+
+    def __enter__(self):
+        # Some SQLite schema alterations need foreign key constraints to be
+        # disabled. Enforce it here for the duration of the schema edition.
+        if not self.connection.disable_constraint_checking():
+            raise NotSupportedError(
+                "SQLite schema editor cannot be used while foreign key "
+                "constraint checks are enabled. Make sure to disable them "
+                "before entering a transaction.atomic() context because "
+                "SQLite does not support disabling them in the middle of "
+                "a multi-statement transaction."
+            )
+        return super().__enter__()
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.connection.check_constraints()
+        super().__exit__(exc_type, exc_value, traceback)
+        self.connection.enable_constraint_checking()
+
+    def quote_value(self, value):
+        # The backend "mostly works" without this function and there are use
+        # cases for compiling Python without the sqlite3 libraries (e.g.
+        # security hardening).
+        try:
+            import sqlite3
+
+            value = sqlite3.adapt(value)
+        except ImportError:
+            pass
+        except sqlite3.ProgrammingError:
+            pass
+        # Manual emulation of SQLite parameter quoting
+        if isinstance(value, bool):
+            return str(int(value))
+        elif isinstance(value, (Decimal, float, int)):
+            return str(value)
+        elif isinstance(value, str):
+            return "'%s'" % value.replace("'", "''")
+        elif value is None:
+            return "NULL"
+        elif isinstance(value, (bytes, bytearray, memoryview)):
+            # Bytes are only allowed for BLOB fields, encoded as string
+            # literals containing hexadecimal data and preceded by a single "X"
+            # character.
+            return "X'%s'" % value.hex()
+        else:
+            raise ValueError(
+                "Cannot quote parameter value %r of type %s" % (value, type(value))
+            )
+
+    def prepare_default(self, value):
+        return self.quote_value(value)
+
+    def _is_referenced_by_fk_constraint(
+        self, table_name, column_name=None, ignore_self=False
+    ):
+        """
+        Return whether or not the provided table name is referenced by another
+        one. If `column_name` is specified, only references pointing to that
+        column are considered. If `ignore_self` is True, self-referential
+        constraints are ignored.
+        """
+        with self.connection.cursor() as cursor:
+            for other_table in self.connection.introspection.get_table_list(cursor):
+                if ignore_self and other_table.name == table_name:
+                    continue
+                relations = self.connection.introspection.get_relations(
+                    cursor, other_table.name
+                )
+                for constraint_column, constraint_table in relations.values():
+                    if constraint_table == table_name and (
+                        column_name is None or constraint_column == column_name
+                    ):
+                        return True
+        return False
+
+    def alter_db_table(
+        self, model, old_db_table, new_db_table, disable_constraints=True
+    ):
+        if (
+            not self.connection.features.supports_atomic_references_rename
+            and disable_constraints
+            and self._is_referenced_by_fk_constraint(old_db_table)
+        ):
+            if self.connection.in_atomic_block:
+                raise NotSupportedError(
+                    (
+                        "Renaming the %r table while in a transaction is not "
+                        "supported on SQLite < 3.26 because it would break referential "
+                        "integrity. Try adding `atomic = False` to the Migration class."
+                    )
+                    % old_db_table
+                )
+            self.connection.enable_constraint_checking()
+            super().alter_db_table(model, old_db_table, new_db_table)
+            self.connection.disable_constraint_checking()
+        else:
+            super().alter_db_table(model, old_db_table, new_db_table)
+
+    def alter_field(self, model, old_field, new_field, strict=False):
+        if not self._field_should_be_altered(old_field, new_field):
+            return
+        old_field_name = old_field.name
+        table_name = model._meta.db_table
+        _, old_column_name = old_field.get_attname_column()
+        if (
+            new_field.name != old_field_name
+            and not self.connection.features.supports_atomic_references_rename
+            and self._is_referenced_by_fk_constraint(
+                table_name, old_column_name, ignore_self=True
+            )
+        ):
+            if self.connection.in_atomic_block:
+                raise NotSupportedError(
+                    (
+                        "Renaming the %r.%r column while in a transaction is not "
+                        "supported on SQLite < 3.26 because it would break referential "
+                        "integrity. Try adding `atomic = False` to the Migration class."
+                    )
+                    % (model._meta.db_table, old_field_name)
+                )
+            with atomic(self.connection.alias):
+                super().alter_field(model, old_field, new_field, strict=strict)
+                # Follow SQLite's documented procedure for performing changes
+                # that don't affect the on-disk content.
+                # https://sqlite.org/lang_altertable.html#otheralter
+                with self.connection.cursor() as cursor:
+                    schema_version = cursor.execute("PRAGMA schema_version").fetchone()[
+                        0
+                    ]
+                    cursor.execute("PRAGMA writable_schema = 1")
+                    references_template = ' REFERENCES "%s" ("%%s") ' % table_name
+                    new_column_name = new_field.get_attname_column()[1]
+                    search = references_template % old_column_name
+                    replacement = references_template % new_column_name
+                    cursor.execute(
+                        "UPDATE sqlite_master SET sql = replace(sql, %s, %s)",
+                        (search, replacement),
+                    )
+                    cursor.execute("PRAGMA schema_version = %d" % (schema_version + 1))
+                    cursor.execute("PRAGMA writable_schema = 0")
+                    # The integrity check will raise an exception and rollback
+                    # the transaction if the sqlite_master updates corrupt the
+                    # database.
+                    cursor.execute("PRAGMA integrity_check")
+            # Perform a VACUUM to refresh the database representation from
+            # the sqlite_master table.
+            with self.connection.cursor() as cursor:
+                cursor.execute("VACUUM")
+        else:
+            super().alter_field(model, old_field, new_field, strict=strict)
+
+    def _remake_table(
+        self, model, create_field=None, delete_field=None, alter_field=None
+    ):
+        """
+        Shortcut to transform a model from old_model into new_model
+
+        This follows the correct procedure to perform non-rename or column
+        addition operations based on SQLite's documentation
+
+        https://www.sqlite.org/lang_altertable.html#caution
+
+        The essential steps are:
+          1. Create a table with the updated definition called "new__app_model"
+          2. Copy the data from the existing "app_model" table to the new table
+          3. Drop the "app_model" table
+          4. Rename the "new__app_model" table to "app_model"
+          5. Restore any index of the previous "app_model" table.
+        """
+        # Self-referential fields must be recreated rather than copied from
+        # the old model to ensure their remote_field.field_name doesn't refer
+        # to an altered field.
+        def is_self_referential(f):
+            return f.is_relation and f.remote_field.model is model
+
+        # Work out the new fields dict / mapping
+        body = {
+            f.name: f.clone() if is_self_referential(f) else f
+            for f in model._meta.local_concrete_fields
+        }
+        # Since mapping might mix column names and default values,
+        # its values must be already quoted.
+        mapping = {
+            f.column: self.quote_name(f.column)
+            for f in model._meta.local_concrete_fields
+        }
+        # This maps field names (not columns) for things like unique_together
+        rename_mapping = {}
+        # If any of the new or altered fields is introducing a new PK,
+        # remove the old one
+        restore_pk_field = None
+        if getattr(create_field, "primary_key", False) or (
+            alter_field and getattr(alter_field[1], "primary_key", False)
+        ):
+            for name, field in list(body.items()):
+                if field.primary_key and not (
+                    # Do not remove the old primary key when an altered field
+                    # that introduces a primary key is the same field.
+                    alter_field
+                    and name == alter_field[1].name
+                ):
+                    field.primary_key = False
+                    restore_pk_field = field
+                    if field.auto_created:
+                        del body[name]
+                        del mapping[field.column]
+        # Add in any created fields
+        if create_field:
+            body[create_field.name] = create_field
+            # Choose a default and insert it into the copy map
+            if not create_field.many_to_many and create_field.concrete:
+                mapping[create_field.column] = self.prepare_default(
+                    self.effective_default(create_field),
+                )
+        # Add in any altered fields
+        if alter_field:
+            old_field, new_field = alter_field
+            body.pop(old_field.name, None)
+            mapping.pop(old_field.column, None)
+            body[new_field.name] = new_field
+            if old_field.null and not new_field.null:
+                case_sql = "coalesce(%(col)s, %(default)s)" % {
+                    "col": self.quote_name(old_field.column),
+                    "default": self.prepare_default(self.effective_default(new_field)),
+                }
+                mapping[new_field.column] = case_sql
+            else:
+                mapping[new_field.column] = self.quote_name(old_field.column)
+            rename_mapping[old_field.name] = new_field.name
+        # Remove any deleted fields
+        if delete_field:
+            del body[delete_field.name]
+            del mapping[delete_field.column]
+            # Remove any implicit M2M tables
+            if (
+                delete_field.many_to_many
+                and delete_field.remote_field.through._meta.auto_created
+            ):
+                return self.delete_model(delete_field.remote_field.through)
+        # Work inside a new app registry
+        apps = Apps()
+
+        # Work out the new value of unique_together, taking renames into
+        # account
+        unique_together = [
+            [rename_mapping.get(n, n) for n in unique]
+            for unique in model._meta.unique_together
+        ]
+
+        # Work out the new value for index_together, taking renames into
+        # account
+        index_together = [
+            [rename_mapping.get(n, n) for n in index]
+            for index in model._meta.index_together
+        ]
+
+        indexes = model._meta.indexes
+        if delete_field:
+            indexes = [
+                index for index in indexes if delete_field.name not in index.fields
+            ]
+
+        constraints = list(model._meta.constraints)
+
+        # Provide isolated instances of the fields to the new model body so
+        # that the existing model's internals aren't interfered with when
+        # the dummy model is constructed.
+        body_copy = copy.deepcopy(body)
+
+        # Construct a new model with the new fields to allow self referential
+        # primary key to resolve to. This model won't ever be materialized as a
+        # table and solely exists for foreign key reference resolution purposes.
+        # This wouldn't be required if the schema editor was operating on model
+        # states instead of rendered models.
+        meta_contents = {
+            "app_label": model._meta.app_label,
+            "db_table": model._meta.db_table,
+            "unique_together": unique_together,
+            "index_together": index_together,
+            "indexes": indexes,
+            "constraints": constraints,
+            "apps": apps,
+        }
+        meta = type("Meta", (), meta_contents)
+        body_copy["Meta"] = meta
+        body_copy["__module__"] = model.__module__
+        type(model._meta.object_name, model.__bases__, body_copy)
+
+        # Construct a model with a renamed table name.
+        body_copy = copy.deepcopy(body)
+        meta_contents = {
+            "app_label": model._meta.app_label,
+            "db_table": "new__%s" % strip_quotes(model._meta.db_table),
+            "unique_together": unique_together,
+            "index_together": index_together,
+            "indexes": indexes,
+            "constraints": constraints,
+            "apps": apps,
+        }
+        meta = type("Meta", (), meta_contents)
+        body_copy["Meta"] = meta
+        body_copy["__module__"] = model.__module__
+        new_model = type("New%s" % model._meta.object_name, model.__bases__, body_copy)
+
+        # Create a new table with the updated schema.
+        self.create_model(new_model)
+
+        # Copy data from the old table into the new table
+        self.execute(
+            "INSERT INTO %s (%s) SELECT %s FROM %s"
+            % (
+                self.quote_name(new_model._meta.db_table),
+                ", ".join(self.quote_name(x) for x in mapping),
+                ", ".join(mapping.values()),
+                self.quote_name(model._meta.db_table),
+            )
+        )
+
+        # Delete the old table to make way for the new
+        self.delete_model(model, handle_autom2m=False)
+
+        # Rename the new table to take way for the old
+        self.alter_db_table(
+            new_model,
+            new_model._meta.db_table,
+            model._meta.db_table,
+            disable_constraints=False,
+        )
+
+        # Run deferred SQL on correct table
+        for sql in self.deferred_sql:
+            self.execute(sql)
+        self.deferred_sql = []
+        # Fix any PK-removed field
+        if restore_pk_field:
+            restore_pk_field.primary_key = True
+
+    def delete_model(self, model, handle_autom2m=True):
+        if handle_autom2m:
+            super().delete_model(model)
+        else:
+            # Delete the table (and only that)
+            self.execute(
+                self.sql_delete_table
+                % {
+                    "table": self.quote_name(model._meta.db_table),
+                }
+            )
+            # Remove all deferred statements referencing the deleted table.
+            for sql in list(self.deferred_sql):
+                if isinstance(sql, Statement) and sql.references_table(
+                    model._meta.db_table
+                ):
+                    self.deferred_sql.remove(sql)
+
+    def add_field(self, model, field):
+        """Create a field on a model."""
+        if (
+            # Primary keys and unique fields are not supported in ALTER TABLE
+            # ADD COLUMN.
+            field.primary_key
+            or field.unique
+            or
+            # Fields with default values cannot by handled by ALTER TABLE ADD
+            # COLUMN statement because DROP DEFAULT is not supported in
+            # ALTER TABLE.
+            not field.null
+            or self.effective_default(field) is not None
+        ):
+            self._remake_table(model, create_field=field)
+        else:
+            super().add_field(model, field)
+
+    def remove_field(self, model, field):
+        """
+        Remove a field from a model. Usually involves deleting a column,
+        but for M2Ms may involve deleting a table.
+        """
+        # M2M fields are a special case
+        if field.many_to_many:
+            # For implicit M2M tables, delete the auto-created table
+            if field.remote_field.through._meta.auto_created:
+                self.delete_model(field.remote_field.through)
+            # For explicit "through" M2M fields, do nothing
+        elif (
+            self.connection.features.can_alter_table_drop_column
+            # Primary keys, unique fields, and foreign keys are not
+            # supported in ALTER TABLE DROP COLUMN.
+            and not field.primary_key
+            and not field.unique
+            and not (field.remote_field and field.db_constraint)
+        ):
+            super().remove_field(model, field)
+        # For everything else, remake.
+        else:
+            # It might not actually have a column behind it
+            if field.db_parameters(connection=self.connection)["type"] is None:
+                return
+            self._remake_table(model, delete_field=field)
+
+    def _alter_field(
+        self,
+        model,
+        old_field,
+        new_field,
+        old_type,
+        new_type,
+        old_db_params,
+        new_db_params,
+        strict=False,
+    ):
+        """Perform a "physical" (non-ManyToMany) field update."""
+        # Use "ALTER TABLE ... RENAME COLUMN" if only the column name
+        # changed and there aren't any constraints.
+        if (
+            self.connection.features.can_alter_table_rename_column
+            and old_field.column != new_field.column
+            and self.column_sql(model, old_field) == self.column_sql(model, new_field)
+            and not (
+                old_field.remote_field
+                and old_field.db_constraint
+                or new_field.remote_field
+                and new_field.db_constraint
+            )
+        ):
+            return self.execute(
+                self._rename_field_sql(
+                    model._meta.db_table, old_field, new_field, new_type
+                )
+            )
+        # Alter by remaking table
+        self._remake_table(model, alter_field=(old_field, new_field))
+        # Rebuild tables with FKs pointing to this field.
+        old_collation = old_db_params.get("collation")
+        new_collation = new_db_params.get("collation")
+        if new_field.unique and (
+            old_type != new_type or old_collation != new_collation
+        ):
+            related_models = set()
+            opts = new_field.model._meta
+            for remote_field in opts.related_objects:
+                # Ignore self-relationship since the table was already rebuilt.
+                if remote_field.related_model == model:
+                    continue
+                if not remote_field.many_to_many:
+                    if remote_field.field_name == new_field.name:
+                        related_models.add(remote_field.related_model)
+                elif new_field.primary_key and remote_field.through._meta.auto_created:
+                    related_models.add(remote_field.through)
+            if new_field.primary_key:
+                for many_to_many in opts.many_to_many:
+                    # Ignore self-relationship since the table was already rebuilt.
+                    if many_to_many.related_model == model:
+                        continue
+                    if many_to_many.remote_field.through._meta.auto_created:
+                        related_models.add(many_to_many.remote_field.through)
+            for related_model in related_models:
+                self._remake_table(related_model)
+
+    def _alter_many_to_many(self, model, old_field, new_field, strict):
+        """Alter M2Ms to repoint their to= endpoints."""
+        if (
+            old_field.remote_field.through._meta.db_table
+            == new_field.remote_field.through._meta.db_table
+        ):
+            # The field name didn't change, but some options did, so we have to
+            # propagate this altering.
+            self._remake_table(
+                old_field.remote_field.through,
+                alter_field=(
+                    # The field that points to the target model is needed, so
+                    # we can tell alter_field to change it - this is
+                    # m2m_reverse_field_name() (as opposed to m2m_field_name(),
+                    # which points to our model).
+                    old_field.remote_field.through._meta.get_field(
+                        old_field.m2m_reverse_field_name()
+                    ),
+                    new_field.remote_field.through._meta.get_field(
+                        new_field.m2m_reverse_field_name()
+                    ),
+                ),
+            )
+            return
+
+        # Make a new through table
+        self.create_model(new_field.remote_field.through)
+        # Copy the data across
+        self.execute(
+            "INSERT INTO %s (%s) SELECT %s FROM %s"
+            % (
+                self.quote_name(new_field.remote_field.through._meta.db_table),
+                ", ".join(
+                    [
+                        "id",
+                        new_field.m2m_column_name(),
+                        new_field.m2m_reverse_name(),
+                    ]
+                ),
+                ", ".join(
+                    [
+                        "id",
+                        old_field.m2m_column_name(),
+                        old_field.m2m_reverse_name(),
+                    ]
+                ),
+                self.quote_name(old_field.remote_field.through._meta.db_table),
+            )
+        )
+        # Delete the old through table
+        self.delete_model(old_field.remote_field.through)
+
+    def add_constraint(self, model, constraint):
+        if isinstance(constraint, UniqueConstraint) and (
+            constraint.condition
+            or constraint.contains_expressions
+            or constraint.include
+            or constraint.deferrable
+        ):
+            super().add_constraint(model, constraint)
+        else:
+            self._remake_table(model)
+
+    def remove_constraint(self, model, constraint):
+        if isinstance(constraint, UniqueConstraint) and (
+            constraint.condition
+            or constraint.contains_expressions
+            or constraint.include
+            or constraint.deferrable
+        ):
+            super().remove_constraint(model, constraint)
+        else:
+            self._remake_table(model)
+
+    def _collate_sql(self, collation):
+        return "COLLATE " + collation