django/db/backends/base/operations.py
import datetime
import decimal
import json
import warnings
from importlib import import_module
import sqlparse
from django.conf import settings
from django.db import NotSupportedError, transaction
from django.db.backends import utils
from django.db.models.expressions import Col
from django.utils import timezone
from django.utils.deprecation import RemovedInDjango60Warning
from django.utils.encoding import force_str
class BaseDatabaseOperations:
"""
Encapsulate backend-specific differences, such as the way a backend
performs ordering or calculates the ID of a recently-inserted row.
"""
compiler_module = "django.db.models.sql.compiler"
# Integer field safe ranges by `internal_type` as documented
# in docs/ref/models/fields.txt.
integer_field_ranges = {
"SmallIntegerField": (-32768, 32767),
"IntegerField": (-2147483648, 2147483647),
"BigIntegerField": (-9223372036854775808, 9223372036854775807),
"PositiveBigIntegerField": (0, 9223372036854775807),
"PositiveSmallIntegerField": (0, 32767),
"PositiveIntegerField": (0, 2147483647),
"SmallAutoField": (-32768, 32767),
"AutoField": (-2147483648, 2147483647),
"BigAutoField": (-9223372036854775808, 9223372036854775807),
}
set_operators = {
"union": "UNION",
"intersection": "INTERSECT",
"difference": "EXCEPT",
}
# Mapping of Field.get_internal_type() (typically the model field's class
# name) to the data type to use for the Cast() function, if different from
# DatabaseWrapper.data_types.
cast_data_types = {}
# CharField data type if the max_length argument isn't provided.
cast_char_field_without_max_length = None
# Start and end points for window expressions.
PRECEDING = "PRECEDING"
FOLLOWING = "FOLLOWING"
UNBOUNDED_PRECEDING = "UNBOUNDED " + PRECEDING
UNBOUNDED_FOLLOWING = "UNBOUNDED " + FOLLOWING
CURRENT_ROW = "CURRENT ROW"
# Prefix for EXPLAIN queries, or None EXPLAIN isn't supported.
explain_prefix = None
def __init__(self, connection):
self.connection = connection
self._cache = None
def autoinc_sql(self, table, column):
"""
Return any SQL needed to support auto-incrementing primary keys, or
None if no SQL is necessary.
This SQL is executed when a table is created.
"""
return None
def bulk_batch_size(self, fields, objs):
"""
Return the maximum allowed batch size for the backend. The fields
are the fields going to be inserted in the batch, the objs contains
all the objects to be inserted.
"""
return len(objs)
def format_for_duration_arithmetic(self, sql):
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a "
"format_for_duration_arithmetic() method."
)
def cache_key_culling_sql(self):
"""
Return an SQL query that retrieves the first cache key greater than the
n smallest.
This is used by the 'db' cache backend to determine where to start
culling.
"""
cache_key = self.quote_name("cache_key")
return f"SELECT {cache_key} FROM %s ORDER BY {cache_key} LIMIT 1 OFFSET %%s"
def unification_cast_sql(self, output_field):
"""
Given a field instance, return the SQL that casts the result of a union
to that type. The resulting string should contain a '%s' placeholder
for the expression being cast.
"""
return "%s"
def date_extract_sql(self, lookup_type, sql, params):
"""
Given a lookup_type of 'year', 'month', or 'day', return the SQL that
extracts a value from the given date field field_name.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a date_extract_sql() "
"method"
)
def date_trunc_sql(self, lookup_type, sql, params, tzname=None):
"""
Given a lookup_type of 'year', 'month', or 'day', return the SQL that
truncates the given date or datetime field field_name to a date object
with only the given specificity.
If `tzname` is provided, the given value is truncated in a specific
timezone.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a date_trunc_sql() "
"method."
)
def datetime_cast_date_sql(self, sql, params, tzname):
"""
Return the SQL to cast a datetime value to date value.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a "
"datetime_cast_date_sql() method."
)
def datetime_cast_time_sql(self, sql, params, tzname):
"""
Return the SQL to cast a datetime value to time value.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a "
"datetime_cast_time_sql() method"
)
def datetime_extract_sql(self, lookup_type, sql, params, tzname):
"""
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute', or
'second', return the SQL that extracts a value from the given
datetime field field_name.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a datetime_extract_sql() "
"method"
)
def datetime_trunc_sql(self, lookup_type, sql, params, tzname):
"""
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute', or
'second', return the SQL that truncates the given datetime field
field_name to a datetime object with only the given specificity.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a datetime_trunc_sql() "
"method"
)
def time_trunc_sql(self, lookup_type, sql, params, tzname=None):
"""
Given a lookup_type of 'hour', 'minute' or 'second', return the SQL
that truncates the given time or datetime field field_name to a time
object with only the given specificity.
If `tzname` is provided, the given value is truncated in a specific
timezone.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a time_trunc_sql() method"
)
def time_extract_sql(self, lookup_type, sql, params):
"""
Given a lookup_type of 'hour', 'minute', or 'second', return the SQL
that extracts a value from the given time field field_name.
"""
return self.date_extract_sql(lookup_type, sql, params)
def deferrable_sql(self):
"""
Return the SQL to make a constraint "initially deferred" during a
CREATE TABLE statement.
"""
return ""
def distinct_sql(self, fields, params):
"""
Return an SQL DISTINCT clause which removes duplicate rows from the
result set. If any fields are given, only check the given fields for
duplicates.
"""
if fields:
raise NotSupportedError(
"DISTINCT ON fields is not supported by this database backend"
)
else:
return ["DISTINCT"], []
def fetch_returned_insert_columns(self, cursor, returning_params):
"""
Given a cursor object that has just performed an INSERT...RETURNING
statement into a table, return the newly created data.
"""
return cursor.fetchone()
def field_cast_sql(self, db_type, internal_type):
"""
Given a column type (e.g. 'BLOB', 'VARCHAR') and an internal type
(e.g. 'GenericIPAddressField'), return the SQL to cast it before using
it in a WHERE statement. The resulting string should contain a '%s'
placeholder for the column being searched against.
"""
warnings.warn(
(
"DatabaseOperations.field_cast_sql() is deprecated use "
"DatabaseOperations.lookup_cast() instead."
),
RemovedInDjango60Warning,
)
return "%s"
def force_group_by(self):
"""
Return a GROUP BY clause to use with a HAVING clause when no grouping
is specified.
"""
return []
def force_no_ordering(self):
"""
Return a list used in the "ORDER BY" clause to force no ordering at
all. Return an empty list to include nothing in the ordering.
"""
return []
def for_update_sql(self, nowait=False, skip_locked=False, of=(), no_key=False):
"""
Return the FOR UPDATE SQL clause to lock rows for an update operation.
"""
return "FOR%s UPDATE%s%s%s" % (
" NO KEY" if no_key else "",
" OF %s" % ", ".join(of) if of else "",
" NOWAIT" if nowait else "",
" SKIP LOCKED" if skip_locked else "",
)
def _get_limit_offset_params(self, low_mark, high_mark):
offset = low_mark or 0
if high_mark is not None:
return (high_mark - offset), offset
elif offset:
return self.connection.ops.no_limit_value(), offset
return None, offset
def limit_offset_sql(self, low_mark, high_mark):
"""Return LIMIT/OFFSET SQL clause."""
limit, offset = self._get_limit_offset_params(low_mark, high_mark)
return " ".join(
sql
for sql in (
("LIMIT %d" % limit) if limit else None,
("OFFSET %d" % offset) if offset else None,
)
if sql
)
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 last_executed_query(self, cursor, sql, params):
"""
Return a string of the query last executed by the given cursor, with
placeholders replaced with actual values.
`sql` is the raw query containing placeholders and `params` is the
sequence of parameters. These are used by default, but this method
exists for database backends to provide a better implementation
according to their own quoting schemes.
"""
# Convert params to contain string values.
def to_string(s):
return force_str(s, strings_only=True, errors="replace")
if isinstance(params, (list, tuple)):
u_params = tuple(to_string(val) for val in params)
elif params is None:
u_params = ()
else:
u_params = {to_string(k): to_string(v) for k, v in params.items()}
return "QUERY = %r - PARAMS = %r" % (sql, u_params)
def last_insert_id(self, cursor, table_name, pk_name):
"""
Given a cursor object that has just performed an INSERT statement into
a table that has an auto-incrementing ID, return the newly created ID.
`pk_name` is the name of the primary-key column.
"""
return cursor.lastrowid
def lookup_cast(self, lookup_type, internal_type=None):
"""
Return the string to use in a query when performing lookups
("contains", "like", etc.). It should contain a '%s' placeholder for
the column being searched against.
"""
return "%s"
def max_in_list_size(self):
"""
Return the maximum number of items that can be passed in a single 'IN'
list condition, or None if the backend does not impose a limit.
"""
return None
def max_name_length(self):
"""
Return the maximum length of table and column names, or None if there
is no limit.
"""
return None
def no_limit_value(self):
"""
Return the value to use for the LIMIT when we are wanting "LIMIT
infinity". Return None if the limit clause can be omitted in this case.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a no_limit_value() method"
)
def pk_default_value(self):
"""
Return the value to use during an INSERT statement to specify that
the field should use its default value.
"""
return "DEFAULT"
def prepare_sql_script(self, sql):
"""
Take an SQL script that may contain multiple lines and return a list
of statements to feed to successive cursor.execute() calls.
Since few databases are able to process raw SQL scripts in a single
cursor.execute() call and PEP 249 doesn't talk about this use case,
the default implementation is conservative.
"""
return [
sqlparse.format(statement, strip_comments=True)
for statement in sqlparse.split(sql)
if statement
]
def process_clob(self, value):
"""
Return the value of a CLOB column, for backends that return a locator
object that requires additional processing.
"""
return value
def return_insert_columns(self, fields):
"""
For backends that support returning columns as part of an insert query,
return the SQL and params to append to the INSERT query. The returned
fragment should contain a format string to hold the appropriate column.
"""
pass
def compiler(self, compiler_name):
"""
Return the SQLCompiler class corresponding to the given name,
in the namespace corresponding to the `compiler_module` attribute
on this backend.
"""
if self._cache is None:
self._cache = import_module(self.compiler_module)
return getattr(self._cache, compiler_name)
def quote_name(self, name):
"""
Return a quoted version of the given table, index, or column name. Do
not quote the given name if it's already been quoted.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a quote_name() method"
)
def regex_lookup(self, lookup_type):
"""
Return the string to use in a query when performing regular expression
lookups (using "regex" or "iregex"). It should contain a '%s'
placeholder for the column being searched against.
If the feature is not supported (or part of it is not supported), raise
NotImplementedError.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations may require a regex_lookup() method"
)
def savepoint_create_sql(self, sid):
"""
Return the SQL for starting a new savepoint. Only required if the
"uses_savepoints" feature is True. The "sid" parameter is a string
for the savepoint id.
"""
return "SAVEPOINT %s" % self.quote_name(sid)
def savepoint_commit_sql(self, sid):
"""
Return the SQL for committing the given savepoint.
"""
return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
def savepoint_rollback_sql(self, sid):
"""
Return the SQL for rolling back the given savepoint.
"""
return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
def set_time_zone_sql(self):
"""
Return the SQL that will set the connection's time zone.
Return '' if the backend doesn't support time zones.
"""
return ""
def sql_flush(self, style, tables, *, reset_sequences=False, allow_cascade=False):
"""
Return a list of SQL statements required to remove all data from
the given database tables (without actually removing the tables
themselves).
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
If `reset_sequences` is True, the list includes SQL statements required
to reset the sequences.
The `allow_cascade` argument determines whether truncation may cascade
to tables with foreign keys pointing the tables being truncated.
PostgreSQL requires a cascade even if these tables are empty.
"""
raise NotImplementedError(
"subclasses of BaseDatabaseOperations must provide an sql_flush() method"
)
def execute_sql_flush(self, sql_list):
"""Execute a list of SQL statements to flush the database."""
with transaction.atomic(
using=self.connection.alias,
savepoint=self.connection.features.can_rollback_ddl,
):
with self.connection.cursor() as cursor:
for sql in sql_list:
cursor.execute(sql)
def sequence_reset_by_name_sql(self, style, sequences):
"""
Return a list of the SQL statements required to reset sequences
passed in `sequences`.
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
"""
return []
def sequence_reset_sql(self, style, model_list):
"""
Return a list of the SQL statements required to reset sequences for
the given models.
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
"""
return [] # No sequence reset required by default.
def start_transaction_sql(self):
"""Return the SQL statement required to start a transaction."""
return "BEGIN;"
def end_transaction_sql(self, success=True):
"""Return the SQL statement required to end a transaction."""
if not success:
return "ROLLBACK;"
return "COMMIT;"
def tablespace_sql(self, tablespace, inline=False):
"""
Return the SQL that will be used in a query to define the tablespace.
Return '' if the backend doesn't support tablespaces.
If `inline` is True, append the SQL to a row; otherwise append it to
the entire CREATE TABLE or CREATE INDEX statement.
"""
return ""
def prep_for_like_query(self, x):
"""Prepare a value for use in a LIKE query."""
return str(x).replace("\\", "\\\\").replace("%", r"\%").replace("_", r"\_")
# Same as prep_for_like_query(), but called for "iexact" matches, which
# need not necessarily be implemented using "LIKE" in the backend.
prep_for_iexact_query = prep_for_like_query
def validate_autopk_value(self, value):
"""
Certain backends do not accept some values for "serial" fields
(for example zero in MySQL). Raise a ValueError if the value is
invalid, otherwise return the validated value.
"""
return value
def adapt_unknown_value(self, value):
"""
Transform a value to something compatible with the backend driver.
This method only depends on the type of the value. It's designed for
cases where the target type isn't known, such as .raw() SQL queries.
As a consequence it may not work perfectly in all circumstances.
"""
if isinstance(value, datetime.datetime): # must be before date
return self.adapt_datetimefield_value(value)
elif isinstance(value, datetime.date):
return self.adapt_datefield_value(value)
elif isinstance(value, datetime.time):
return self.adapt_timefield_value(value)
elif isinstance(value, decimal.Decimal):
return self.adapt_decimalfield_value(value)
else:
return value
def adapt_integerfield_value(self, value, internal_type):
return value
def adapt_datefield_value(self, value):
"""
Transform a date value to an object compatible with what is expected
by the backend driver for date columns.
"""
if value is None:
return None
return str(value)
def adapt_datetimefield_value(self, value):
"""
Transform a datetime value to an object compatible with what is expected
by the backend driver for datetime columns.
"""
if value is None:
return None
return str(value)
def adapt_timefield_value(self, value):
"""
Transform a time value to an object compatible with what is expected
by the backend driver for time columns.
"""
if value is None:
return None
if timezone.is_aware(value):
raise ValueError("Django does not support timezone-aware times.")
return str(value)
def adapt_decimalfield_value(self, value, max_digits=None, decimal_places=None):
"""
Transform a decimal.Decimal value to an object compatible with what is
expected by the backend driver for decimal (numeric) columns.
"""
return utils.format_number(value, max_digits, decimal_places)
def adapt_ipaddressfield_value(self, value):
"""
Transform a string representation of an IP address into the expected
type for the backend driver.
"""
return value or None
def adapt_json_value(self, value, encoder):
return json.dumps(value, cls=encoder)
def year_lookup_bounds_for_date_field(self, value, iso_year=False):
"""
Return a two-elements list with the lower and upper bound to be used
with a BETWEEN operator to query a DateField value using a year
lookup.
`value` is an int, containing the looked-up year.
If `iso_year` is True, return bounds for ISO-8601 week-numbering years.
"""
if iso_year:
first = datetime.date.fromisocalendar(value, 1, 1)
second = datetime.date.fromisocalendar(
value + 1, 1, 1
) - datetime.timedelta(days=1)
else:
first = datetime.date(value, 1, 1)
second = datetime.date(value, 12, 31)
first = self.adapt_datefield_value(first)
second = self.adapt_datefield_value(second)
return [first, second]
def year_lookup_bounds_for_datetime_field(self, value, iso_year=False):
"""
Return a two-elements list with the lower and upper bound to be used
with a BETWEEN operator to query a DateTimeField value using a year
lookup.
`value` is an int, containing the looked-up year.
If `iso_year` is True, return bounds for ISO-8601 week-numbering years.
"""
if iso_year:
first = datetime.datetime.fromisocalendar(value, 1, 1)
second = datetime.datetime.fromisocalendar(
value + 1, 1, 1
) - datetime.timedelta(microseconds=1)
else:
first = datetime.datetime(value, 1, 1)
second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
if settings.USE_TZ:
tz = timezone.get_current_timezone()
first = timezone.make_aware(first, tz)
second = timezone.make_aware(second, tz)
first = self.adapt_datetimefield_value(first)
second = self.adapt_datetimefield_value(second)
return [first, second]
def get_db_converters(self, expression):
"""
Return a list of functions needed to convert field data.
Some field types on some backends do not provide data in the correct
format, this is the hook for converter functions.
"""
return []
def convert_durationfield_value(self, value, expression, connection):
if value is not None:
return datetime.timedelta(0, 0, value)
def check_expression_support(self, expression):
"""
Check that the backend supports the provided expression.
This is used on specific backends to rule out known expressions
that have problematic or nonexistent implementations. If the
expression has a known problem, the backend should raise
NotSupportedError.
"""
pass
def conditional_expression_supported_in_where_clause(self, expression):
"""
Return True, if the conditional expression is supported in the WHERE
clause.
"""
return True
def combine_expression(self, connector, sub_expressions):
"""
Combine a list of subexpressions into a single expression, using
the provided connecting operator. This is required because operators
can vary between backends (e.g., Oracle with %% and &) and between
subexpression types (e.g., date expressions).
"""
conn = " %s " % connector
return conn.join(sub_expressions)
def combine_duration_expression(self, connector, sub_expressions):
return self.combine_expression(connector, sub_expressions)
def binary_placeholder_sql(self, value):
"""
Some backends require special syntax to insert binary content (MySQL
for example uses '_binary %s').
"""
return "%s"
def modify_insert_params(self, placeholder, params):
"""
Allow modification of insert parameters. Needed for Oracle Spatial
backend due to #10888.
"""
return params
def integer_field_range(self, internal_type):
"""
Given an integer field internal type (e.g. 'PositiveIntegerField'),
return a tuple of the (min_value, max_value) form representing the
range of the column type bound to the field.
"""
return self.integer_field_ranges[internal_type]
def subtract_temporals(self, internal_type, lhs, rhs):
if self.connection.features.supports_temporal_subtraction:
lhs_sql, lhs_params = lhs
rhs_sql, rhs_params = rhs
return "(%s - %s)" % (lhs_sql, rhs_sql), (*lhs_params, *rhs_params)
raise NotSupportedError(
"This backend does not support %s subtraction." % internal_type
)
def window_frame_value(self, value):
if isinstance(value, int):
if value == 0:
return self.CURRENT_ROW
elif value < 0:
return "%d %s" % (abs(value), self.PRECEDING)
else:
return "%d %s" % (value, self.FOLLOWING)
def window_frame_rows_start_end(self, start=None, end=None):
"""
Return SQL for start and end points in an OVER clause window frame.
"""
if isinstance(start, int) and isinstance(end, int) and start > end:
raise ValueError("start cannot be greater than end.")
if start is not None and not isinstance(start, int):
raise ValueError(
f"start argument must be an integer, zero, or None, but got '{start}'."
)
if end is not None and not isinstance(end, int):
raise ValueError(
f"end argument must be an integer, zero, or None, but got '{end}'."
)
start_ = self.window_frame_value(start) or self.UNBOUNDED_PRECEDING
end_ = self.window_frame_value(end) or self.UNBOUNDED_FOLLOWING
return start_, end_
def window_frame_range_start_end(self, start=None, end=None):
if (start is not None and not isinstance(start, int)) or (
isinstance(start, int) and start > 0
):
raise ValueError(
"start argument must be a negative integer, zero, or None, "
"but got '%s'." % start
)
if (end is not None and not isinstance(end, int)) or (
isinstance(end, int) and end < 0
):
raise ValueError(
"end argument must be a positive integer, zero, or None, but got '%s'."
% end
)
start_ = self.window_frame_value(start) or self.UNBOUNDED_PRECEDING
end_ = self.window_frame_value(end) or self.UNBOUNDED_FOLLOWING
features = self.connection.features
if features.only_supports_unbounded_with_preceding_and_following and (
(start and start < 0) or (end and end > 0)
):
raise NotSupportedError(
"%s only supports UNBOUNDED together with PRECEDING and "
"FOLLOWING." % self.connection.display_name
)
return start_, end_
def explain_query_prefix(self, format=None, **options):
if not self.connection.features.supports_explaining_query_execution:
raise NotSupportedError(
"This backend does not support explaining query execution."
)
if format:
supported_formats = self.connection.features.supported_explain_formats
normalized_format = format.upper()
if normalized_format not in supported_formats:
msg = "%s is not a recognized format." % normalized_format
if supported_formats:
msg += " Allowed formats: %s" % ", ".join(sorted(supported_formats))
else:
msg += (
f" {self.connection.display_name} does not support any formats."
)
raise ValueError(msg)
if options:
raise ValueError("Unknown options: %s" % ", ".join(sorted(options.keys())))
return self.explain_prefix
def insert_statement(self, on_conflict=None):
return "INSERT INTO"
def on_conflict_suffix_sql(self, fields, on_conflict, update_fields, unique_fields):
return ""
def prepare_join_on_clause(self, lhs_table, lhs_field, rhs_table, rhs_field):
lhs_expr = Col(lhs_table, lhs_field)
rhs_expr = Col(rhs_table, rhs_field)
return lhs_expr, rhs_expr