296 lines
12 KiB
Python
296 lines
12 KiB
Python
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from django.db.backends.utils import names_digest, split_identifier
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from django.db.models.expressions import Col, ExpressionList, F, Func, OrderBy
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from django.db.models.functions import Collate
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from django.db.models.query_utils import Q
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from django.db.models.sql import Query
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from django.utils.functional import partition
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__all__ = ["Index"]
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class Index:
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suffix = "idx"
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# The max length of the name of the index (restricted to 30 for
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# cross-database compatibility with Oracle)
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max_name_length = 30
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def __init__(
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self,
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*expressions,
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fields=(),
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name=None,
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db_tablespace=None,
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opclasses=(),
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condition=None,
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include=None,
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):
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if opclasses and not name:
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raise ValueError("An index must be named to use opclasses.")
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if not isinstance(condition, (type(None), Q)):
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raise ValueError("Index.condition must be a Q instance.")
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if condition and not name:
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raise ValueError("An index must be named to use condition.")
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if not isinstance(fields, (list, tuple)):
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raise ValueError("Index.fields must be a list or tuple.")
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if not isinstance(opclasses, (list, tuple)):
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raise ValueError("Index.opclasses must be a list or tuple.")
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if not expressions and not fields:
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raise ValueError(
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"At least one field or expression is required to define an index."
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)
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if expressions and fields:
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raise ValueError(
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"Index.fields and expressions are mutually exclusive.",
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)
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if expressions and not name:
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raise ValueError("An index must be named to use expressions.")
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if expressions and opclasses:
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raise ValueError(
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"Index.opclasses cannot be used with expressions. Use "
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"django.contrib.postgres.indexes.OpClass() instead."
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)
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if opclasses and len(fields) != len(opclasses):
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raise ValueError(
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"Index.fields and Index.opclasses must have the same number of "
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"elements."
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)
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if fields and not all(isinstance(field, str) for field in fields):
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raise ValueError("Index.fields must contain only strings with field names.")
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if include and not name:
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raise ValueError("A covering index must be named.")
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if not isinstance(include, (type(None), list, tuple)):
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raise ValueError("Index.include must be a list or tuple.")
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self.fields = list(fields)
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# A list of 2-tuple with the field name and ordering ('' or 'DESC').
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self.fields_orders = [
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(field_name[1:], "DESC") if field_name.startswith("-") else (field_name, "")
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for field_name in self.fields
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]
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self.name = name or ""
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self.db_tablespace = db_tablespace
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self.opclasses = opclasses
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self.condition = condition
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self.include = tuple(include) if include else ()
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self.expressions = tuple(
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F(expression) if isinstance(expression, str) else expression
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for expression in expressions
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)
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@property
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def contains_expressions(self):
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return bool(self.expressions)
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def _get_condition_sql(self, model, schema_editor):
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if self.condition is None:
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return None
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query = Query(model=model, alias_cols=False)
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where = query.build_where(self.condition)
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compiler = query.get_compiler(connection=schema_editor.connection)
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sql, params = where.as_sql(compiler, schema_editor.connection)
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return sql % tuple(schema_editor.quote_value(p) for p in params)
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def create_sql(self, model, schema_editor, using="", **kwargs):
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include = [
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model._meta.get_field(field_name).column for field_name in self.include
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]
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condition = self._get_condition_sql(model, schema_editor)
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if self.expressions:
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index_expressions = []
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for expression in self.expressions:
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index_expression = IndexExpression(expression)
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index_expression.set_wrapper_classes(schema_editor.connection)
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index_expressions.append(index_expression)
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expressions = ExpressionList(*index_expressions).resolve_expression(
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Query(model, alias_cols=False),
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)
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fields = None
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col_suffixes = None
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else:
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fields = [
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model._meta.get_field(field_name)
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for field_name, _ in self.fields_orders
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]
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if schema_editor.connection.features.supports_index_column_ordering:
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col_suffixes = [order[1] for order in self.fields_orders]
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else:
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col_suffixes = [""] * len(self.fields_orders)
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expressions = None
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return schema_editor._create_index_sql(
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model,
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fields=fields,
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name=self.name,
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using=using,
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db_tablespace=self.db_tablespace,
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col_suffixes=col_suffixes,
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opclasses=self.opclasses,
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condition=condition,
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include=include,
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expressions=expressions,
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**kwargs,
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)
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def remove_sql(self, model, schema_editor, **kwargs):
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return schema_editor._delete_index_sql(model, self.name, **kwargs)
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def deconstruct(self):
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path = "%s.%s" % (self.__class__.__module__, self.__class__.__name__)
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path = path.replace("django.db.models.indexes", "django.db.models")
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kwargs = {"name": self.name}
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if self.fields:
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kwargs["fields"] = self.fields
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if self.db_tablespace is not None:
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kwargs["db_tablespace"] = self.db_tablespace
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if self.opclasses:
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kwargs["opclasses"] = self.opclasses
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if self.condition:
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kwargs["condition"] = self.condition
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if self.include:
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kwargs["include"] = self.include
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return (path, self.expressions, kwargs)
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def clone(self):
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"""Create a copy of this Index."""
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_, args, kwargs = self.deconstruct()
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return self.__class__(*args, **kwargs)
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def set_name_with_model(self, model):
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"""
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Generate a unique name for the index.
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The name is divided into 3 parts - table name (12 chars), field name
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(8 chars) and unique hash + suffix (10 chars). Each part is made to
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fit its size by truncating the excess length.
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"""
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_, table_name = split_identifier(model._meta.db_table)
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column_names = [
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model._meta.get_field(field_name).column
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for field_name, order in self.fields_orders
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]
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column_names_with_order = [
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(("-%s" if order else "%s") % column_name)
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for column_name, (field_name, order) in zip(
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column_names, self.fields_orders
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)
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]
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# The length of the parts of the name is based on the default max
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# length of 30 characters.
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hash_data = [table_name] + column_names_with_order + [self.suffix]
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self.name = "%s_%s_%s" % (
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table_name[:11],
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column_names[0][:7],
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"%s_%s" % (names_digest(*hash_data, length=6), self.suffix),
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)
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if len(self.name) > self.max_name_length:
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raise ValueError(
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"Index too long for multiple database support. Is self.suffix "
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"longer than 3 characters?"
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)
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if self.name[0] == "_" or self.name[0].isdigit():
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self.name = "D%s" % self.name[1:]
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def __repr__(self):
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return "<%s:%s%s%s%s%s%s%s>" % (
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self.__class__.__qualname__,
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"" if not self.fields else " fields=%s" % repr(self.fields),
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"" if not self.expressions else " expressions=%s" % repr(self.expressions),
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"" if not self.name else " name=%s" % repr(self.name),
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""
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if self.db_tablespace is None
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else " db_tablespace=%s" % repr(self.db_tablespace),
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"" if self.condition is None else " condition=%s" % self.condition,
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"" if not self.include else " include=%s" % repr(self.include),
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"" if not self.opclasses else " opclasses=%s" % repr(self.opclasses),
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)
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def __eq__(self, other):
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if self.__class__ == other.__class__:
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return self.deconstruct() == other.deconstruct()
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return NotImplemented
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class IndexExpression(Func):
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"""Order and wrap expressions for CREATE INDEX statements."""
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template = "%(expressions)s"
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wrapper_classes = (OrderBy, Collate)
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def set_wrapper_classes(self, connection=None):
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# Some databases (e.g. MySQL) treats COLLATE as an indexed expression.
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if connection and connection.features.collate_as_index_expression:
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self.wrapper_classes = tuple(
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[
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wrapper_cls
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for wrapper_cls in self.wrapper_classes
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if wrapper_cls is not Collate
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]
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)
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@classmethod
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def register_wrappers(cls, *wrapper_classes):
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cls.wrapper_classes = wrapper_classes
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def resolve_expression(
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self,
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query=None,
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allow_joins=True,
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reuse=None,
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summarize=False,
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for_save=False,
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):
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expressions = list(self.flatten())
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# Split expressions and wrappers.
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index_expressions, wrappers = partition(
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lambda e: isinstance(e, self.wrapper_classes),
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expressions,
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)
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wrapper_types = [type(wrapper) for wrapper in wrappers]
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if len(wrapper_types) != len(set(wrapper_types)):
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raise ValueError(
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"Multiple references to %s can't be used in an indexed "
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"expression."
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% ", ".join(
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[wrapper_cls.__qualname__ for wrapper_cls in self.wrapper_classes]
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)
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)
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if expressions[1 : len(wrappers) + 1] != wrappers:
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raise ValueError(
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"%s must be topmost expressions in an indexed expression."
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% ", ".join(
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[wrapper_cls.__qualname__ for wrapper_cls in self.wrapper_classes]
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)
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)
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# Wrap expressions in parentheses if they are not column references.
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root_expression = index_expressions[1]
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resolve_root_expression = root_expression.resolve_expression(
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query,
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allow_joins,
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reuse,
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summarize,
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for_save,
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)
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if not isinstance(resolve_root_expression, Col):
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root_expression = Func(root_expression, template="(%(expressions)s)")
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if wrappers:
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# Order wrappers and set their expressions.
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wrappers = sorted(
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wrappers,
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key=lambda w: self.wrapper_classes.index(type(w)),
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)
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wrappers = [wrapper.copy() for wrapper in wrappers]
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for i, wrapper in enumerate(wrappers[:-1]):
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wrapper.set_source_expressions([wrappers[i + 1]])
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# Set the root expression on the deepest wrapper.
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wrappers[-1].set_source_expressions([root_expression])
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self.set_source_expressions([wrappers[0]])
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else:
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# Use the root expression, if there are no wrappers.
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self.set_source_expressions([root_expression])
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return super().resolve_expression(
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query, allow_joins, reuse, summarize, for_save
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)
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def as_sqlite(self, compiler, connection, **extra_context):
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# Casting to numeric is unnecessary.
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return self.as_sql(compiler, connection, **extra_context)
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