Source code for django.contrib.postgres.constraints

from django.db import NotSupportedError
from django.db.backends.ddl_references import Statement, Table
from django.db.models import Deferrable, F, Q
from django.db.models.constraints import BaseConstraint
from django.db.models.sql import Query

__all__ = ['ExclusionConstraint']

[docs]class ExclusionConstraint(BaseConstraint): template = 'CONSTRAINT %(name)s EXCLUDE USING %(index_type)s (%(expressions)s)%(include)s%(where)s%(deferrable)s' def __init__( self, *, name, expressions, index_type=None, condition=None, deferrable=None, include=None, opclasses=(), ): if index_type and index_type.lower() not in {'gist', 'spgist'}: raise ValueError( 'Exclusion constraints only support GiST or SP-GiST indexes.' ) if not expressions: raise ValueError( 'At least one expression is required to define an exclusion ' 'constraint.' ) if not all( isinstance(expr, (list, tuple)) and len(expr) == 2 for expr in expressions ): raise ValueError('The expressions must be a list of 2-tuples.') if not isinstance(condition, (type(None), Q)): raise ValueError( 'ExclusionConstraint.condition must be a Q instance.' ) if condition and deferrable: raise ValueError( 'ExclusionConstraint with conditions cannot be deferred.' ) if not isinstance(deferrable, (type(None), Deferrable)): raise ValueError( 'ExclusionConstraint.deferrable must be a Deferrable instance.' ) if not isinstance(include, (type(None), list, tuple)): raise ValueError( 'ExclusionConstraint.include must be a list or tuple.' ) if include and index_type and index_type.lower() != 'gist': raise ValueError( 'Covering exclusion constraints only support GiST indexes.' ) if not isinstance(opclasses, (list, tuple)): raise ValueError( 'ExclusionConstraint.opclasses must be a list or tuple.' ) if opclasses and len(expressions) != len(opclasses): raise ValueError( 'ExclusionConstraint.expressions and ' 'ExclusionConstraint.opclasses must have the same number of ' 'elements.' ) self.expressions = expressions self.index_type = index_type or 'GIST' self.condition = condition self.deferrable = deferrable self.include = tuple(include) if include else () self.opclasses = opclasses super().__init__(name=name) def _get_expression_sql(self, compiler, schema_editor, query): expressions = [] for idx, (expression, operator) in enumerate(self.expressions): if isinstance(expression, str): expression = F(expression) expression = expression.resolve_expression(query=query) sql, params = compiler.compile(expression) try: opclass = self.opclasses[idx] if opclass: sql = '%s %s' % (sql, opclass) except IndexError: pass sql = sql % tuple(schema_editor.quote_value(p) for p in params) expressions.append('%s WITH %s' % (sql, operator)) return expressions def _get_condition_sql(self, compiler, schema_editor, query): if self.condition is None: return None where = query.build_where(self.condition) sql, params = where.as_sql(compiler, schema_editor.connection) return sql % tuple(schema_editor.quote_value(p) for p in params) def constraint_sql(self, model, schema_editor): query = Query(model, alias_cols=False) compiler = query.get_compiler(connection=schema_editor.connection) expressions = self._get_expression_sql(compiler, schema_editor, query) condition = self._get_condition_sql(compiler, schema_editor, query) include = [model._meta.get_field(field_name).column for field_name in self.include] return self.template % { 'name': schema_editor.quote_name(, 'index_type': self.index_type, 'expressions': ', '.join(expressions), 'include': schema_editor._index_include_sql(model, include), 'where': ' WHERE (%s)' % condition if condition else '', 'deferrable': schema_editor._deferrable_constraint_sql(self.deferrable), } def create_sql(self, model, schema_editor): self.check_supported(schema_editor) return Statement( 'ALTER TABLE %(table)s ADD %(constraint)s', table=Table(model._meta.db_table, schema_editor.quote_name), constraint=self.constraint_sql(model, schema_editor), ) def remove_sql(self, model, schema_editor): return schema_editor._delete_constraint_sql( schema_editor.sql_delete_check, model, schema_editor.quote_name(, ) def check_supported(self, schema_editor): if self.include and not schema_editor.connection.features.supports_covering_gist_indexes: raise NotSupportedError( 'Covering exclusion constraints requires PostgreSQL 12+.' ) def deconstruct(self): path, args, kwargs = super().deconstruct() kwargs['expressions'] = self.expressions if self.condition is not None: kwargs['condition'] = self.condition if self.index_type.lower() != 'gist': kwargs['index_type'] = self.index_type if self.deferrable: kwargs['deferrable'] = self.deferrable if self.include: kwargs['include'] = self.include if self.opclasses: kwargs['opclasses'] = self.opclasses return path, args, kwargs def __eq__(self, other): if isinstance(other, self.__class__): return ( == and self.index_type == other.index_type and self.expressions == other.expressions and self.condition == other.condition and self.deferrable == other.deferrable and self.include == other.include and self.opclasses == other.opclasses ) return super().__eq__(other) def __repr__(self): return '<%s: index_type=%s, expressions=%s%s%s%s%s>' % ( self.__class__.__qualname__, self.index_type, self.expressions, '' if self.condition is None else ', condition=%s' % self.condition, '' if self.deferrable is None else ', deferrable=%s' % self.deferrable, '' if not self.include else ', include=%s' % repr(self.include), '' if not self.opclasses else ', opclasses=%s' % repr(self.opclasses), )
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