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107 lines
4.2 KiB
Python
107 lines
4.2 KiB
Python
5 years ago
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from django.db.backends.ddl_references import Statement, Table
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from django.db.models import F, Q
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from django.db.models.constraints import BaseConstraint
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from django.db.models.sql import Query
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__all__ = ['ExclusionConstraint']
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class ExclusionConstraint(BaseConstraint):
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template = 'CONSTRAINT %(name)s EXCLUDE USING %(index_type)s (%(expressions)s)%(where)s'
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def __init__(self, *, name, expressions, index_type=None, condition=None):
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if index_type and index_type.lower() not in {'gist', 'spgist'}:
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raise ValueError(
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'Exclusion constraints only support GiST or SP-GiST indexes.'
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)
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if not expressions:
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raise ValueError(
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'At least one expression is required to define an exclusion '
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'constraint.'
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)
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if not all(
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isinstance(expr, (list, tuple)) and len(expr) == 2
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for expr in expressions
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):
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raise ValueError('The expressions must be a list of 2-tuples.')
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if not isinstance(condition, (type(None), Q)):
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raise ValueError(
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'ExclusionConstraint.condition must be a Q instance.'
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)
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self.expressions = expressions
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self.index_type = index_type or 'GIST'
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self.condition = condition
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super().__init__(name=name)
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def _get_expression_sql(self, compiler, connection, query):
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expressions = []
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for expression, operator in self.expressions:
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if isinstance(expression, str):
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expression = F(expression)
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if isinstance(expression, F):
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expression = expression.resolve_expression(query=query, simple_col=True)
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else:
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expression = expression.resolve_expression(query=query)
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sql, params = expression.as_sql(compiler, connection)
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expressions.append('%s WITH %s' % (sql % params, operator))
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return expressions
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def _get_condition_sql(self, compiler, schema_editor, query):
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if self.condition is None:
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return None
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where = query.build_where(self.condition)
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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 constraint_sql(self, model, schema_editor):
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query = Query(model)
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compiler = query.get_compiler(connection=schema_editor.connection)
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expressions = self._get_expression_sql(compiler, schema_editor.connection, query)
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condition = self._get_condition_sql(compiler, schema_editor, query)
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return self.template % {
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'name': schema_editor.quote_name(self.name),
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'index_type': self.index_type,
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'expressions': ', '.join(expressions),
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'where': ' WHERE (%s)' % condition if condition else '',
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}
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def create_sql(self, model, schema_editor):
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return Statement(
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'ALTER TABLE %(table)s ADD %(constraint)s',
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table=Table(model._meta.db_table, schema_editor.quote_name),
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constraint=self.constraint_sql(model, schema_editor),
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)
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def remove_sql(self, model, schema_editor):
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return schema_editor._delete_constraint_sql(
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schema_editor.sql_delete_check,
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model,
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schema_editor.quote_name(self.name),
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)
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def deconstruct(self):
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path, args, kwargs = super().deconstruct()
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kwargs['expressions'] = self.expressions
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if self.condition is not None:
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kwargs['condition'] = self.condition
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if self.index_type.lower() != 'gist':
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kwargs['index_type'] = self.index_type
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return path, args, kwargs
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def __eq__(self, other):
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return (
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isinstance(other, self.__class__) and
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self.name == other.name and
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self.index_type == other.index_type and
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self.expressions == other.expressions and
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self.condition == other.condition
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)
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def __repr__(self):
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return '<%s: index_type=%s, expressions=%s%s>' % (
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self.__class__.__qualname__,
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self.index_type,
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self.expressions,
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'' if self.condition is None else ', condition=%s' % self.condition,
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)
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