420 lines
16 KiB
Python
420 lines
16 KiB
Python
"""
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Code to manage the creation and SQL rendering of 'where' constraints.
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"""
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from __future__ import absolute_import
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import datetime
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from itertools import repeat
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from django.conf import settings
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from django.db.models.fields import DateTimeField, Field
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from django.db.models.sql.datastructures import EmptyResultSet, Empty
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from django.db.models.sql.aggregates import Aggregate
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from django.utils.itercompat import is_iterator
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from django.utils.six.moves import xrange
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from django.utils import timezone
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from django.utils import tree
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# Connection types
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AND = 'AND'
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OR = 'OR'
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class EmptyShortCircuit(Exception):
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"""
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Internal exception used to indicate that a "matches nothing" node should be
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added to the where-clause.
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"""
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pass
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class WhereNode(tree.Node):
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"""
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Used to represent the SQL where-clause.
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The class is tied to the Query class that created it (in order to create
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the correct SQL).
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A child is usually a tuple of:
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(Constraint(alias, targetcol, field), lookup_type, value)
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where value can be either raw Python value, or Query, ExpressionNode or
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something else knowing how to turn itself into SQL.
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However, a child could also be any class with as_sql() and either
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relabeled_clone() method or relabel_aliases() and clone() methods. The
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second alternative should be used if the alias is not the only mutable
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variable.
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"""
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default = AND
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def _prepare_data(self, data):
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"""
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Prepare data for addition to the tree. If the data is a list or tuple,
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it is expected to be of the form (obj, lookup_type, value), where obj
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is a Constraint object, and is then slightly munged before being
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stored (to avoid storing any reference to field objects). Otherwise,
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the 'data' is stored unchanged and can be any class with an 'as_sql()'
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method.
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"""
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if not isinstance(data, (list, tuple)):
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return data
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obj, lookup_type, value = data
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if is_iterator(value):
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# Consume any generators immediately, so that we can determine
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# emptiness and transform any non-empty values correctly.
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value = list(value)
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# The "value_annotation" parameter is used to pass auxilliary information
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# about the value(s) to the query construction. Specifically, datetime
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# and empty values need special handling. Other types could be used
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# here in the future (using Python types is suggested for consistency).
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if (isinstance(value, datetime.datetime)
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or (isinstance(obj.field, DateTimeField) and lookup_type != 'isnull')):
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value_annotation = datetime.datetime
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elif hasattr(value, 'value_annotation'):
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value_annotation = value.value_annotation
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else:
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value_annotation = bool(value)
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if hasattr(obj, "prepare"):
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value = obj.prepare(lookup_type, value)
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return (obj, lookup_type, value_annotation, value)
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def as_sql(self, qn, connection):
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"""
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Returns the SQL version of the where clause and the value to be
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substituted in. Returns '', [] if this node matches everything,
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None, [] if this node is empty, and raises EmptyResultSet if this
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node can't match anything.
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"""
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# Note that the logic here is made slightly more complex than
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# necessary because there are two kind of empty nodes: Nodes
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# containing 0 children, and nodes that are known to match everything.
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# A match-everything node is different than empty node (which also
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# technically matches everything) for backwards compatibility reasons.
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# Refs #5261.
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result = []
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result_params = []
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everything_childs, nothing_childs = 0, 0
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non_empty_childs = len(self.children)
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for child in self.children:
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try:
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if hasattr(child, 'as_sql'):
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sql, params = child.as_sql(qn=qn, connection=connection)
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else:
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# A leaf node in the tree.
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sql, params = self.make_atom(child, qn, connection)
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except EmptyResultSet:
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nothing_childs += 1
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else:
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if sql:
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result.append(sql)
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result_params.extend(params)
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else:
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if sql is None:
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# Skip empty childs totally.
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non_empty_childs -= 1
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continue
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everything_childs += 1
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# Check if this node matches nothing or everything.
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# First check the amount of full nodes and empty nodes
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# to make this node empty/full.
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if self.connector == AND:
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full_needed, empty_needed = non_empty_childs, 1
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else:
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full_needed, empty_needed = 1, non_empty_childs
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# Now, check if this node is full/empty using the
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# counts.
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if empty_needed - nothing_childs <= 0:
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if self.negated:
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return '', []
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else:
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raise EmptyResultSet
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if full_needed - everything_childs <= 0:
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if self.negated:
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raise EmptyResultSet
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else:
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return '', []
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if non_empty_childs == 0:
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# All the child nodes were empty, so this one is empty, too.
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return None, []
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conn = ' %s ' % self.connector
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sql_string = conn.join(result)
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if sql_string:
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if self.negated:
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# Some backends (Oracle at least) need parentheses
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# around the inner SQL in the negated case, even if the
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# inner SQL contains just a single expression.
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sql_string = 'NOT (%s)' % sql_string
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elif len(result) > 1:
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sql_string = '(%s)' % sql_string
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return sql_string, result_params
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def get_cols(self):
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cols = []
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for child in self.children:
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if hasattr(child, 'get_cols'):
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cols.extend(child.get_cols())
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else:
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if isinstance(child[0], Constraint):
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cols.append((child[0].alias, child[0].col))
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if hasattr(child[3], 'get_cols'):
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cols.extend(child[3].get_cols())
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return cols
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def make_atom(self, child, qn, connection):
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"""
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Turn a tuple (Constraint(table_alias, column_name, db_type),
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lookup_type, value_annotation, params) into valid SQL.
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The first item of the tuple may also be an Aggregate.
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Returns the string for the SQL fragment and the parameters to use for
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it.
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"""
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lvalue, lookup_type, value_annotation, params_or_value = child
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field_internal_type = lvalue.field.get_internal_type() if lvalue.field else None
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if isinstance(lvalue, Constraint):
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try:
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lvalue, params = lvalue.process(lookup_type, params_or_value, connection)
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except EmptyShortCircuit:
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raise EmptyResultSet
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elif isinstance(lvalue, Aggregate):
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params = lvalue.field.get_db_prep_lookup(lookup_type, params_or_value, connection)
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else:
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raise TypeError("'make_atom' expects a Constraint or an Aggregate "
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"as the first item of its 'child' argument.")
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if isinstance(lvalue, tuple):
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# A direct database column lookup.
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field_sql, field_params = self.sql_for_columns(lvalue, qn, connection, field_internal_type), []
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else:
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# A smart object with an as_sql() method.
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field_sql, field_params = lvalue.as_sql(qn, connection)
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is_datetime_field = value_annotation is datetime.datetime
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cast_sql = connection.ops.datetime_cast_sql() if is_datetime_field else '%s'
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if hasattr(params, 'as_sql'):
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extra, params = params.as_sql(qn, connection)
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cast_sql = ''
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else:
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extra = ''
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params = field_params + params
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if (len(params) == 1 and params[0] == '' and lookup_type == 'exact'
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and connection.features.interprets_empty_strings_as_nulls):
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lookup_type = 'isnull'
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value_annotation = True
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if lookup_type in connection.operators:
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format = "%s %%s %%s" % (connection.ops.lookup_cast(lookup_type),)
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return (format % (field_sql,
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connection.operators[lookup_type] % cast_sql,
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extra), params)
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if lookup_type == 'in':
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if not value_annotation:
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raise EmptyResultSet
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if extra:
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return ('%s IN %s' % (field_sql, extra), params)
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max_in_list_size = connection.ops.max_in_list_size()
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if max_in_list_size and len(params) > max_in_list_size:
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# Break up the params list into an OR of manageable chunks.
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in_clause_elements = ['(']
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for offset in xrange(0, len(params), max_in_list_size):
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if offset > 0:
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in_clause_elements.append(' OR ')
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in_clause_elements.append('%s IN (' % field_sql)
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group_size = min(len(params) - offset, max_in_list_size)
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param_group = ', '.join(repeat('%s', group_size))
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in_clause_elements.append(param_group)
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in_clause_elements.append(')')
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in_clause_elements.append(')')
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return ''.join(in_clause_elements), params
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else:
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return ('%s IN (%s)' % (field_sql,
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', '.join(repeat('%s', len(params)))),
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params)
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elif lookup_type in ('range', 'year'):
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return ('%s BETWEEN %%s and %%s' % field_sql, params)
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elif is_datetime_field and lookup_type in ('month', 'day', 'week_day',
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'hour', 'minute', 'second'):
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tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
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sql, tz_params = connection.ops.datetime_extract_sql(lookup_type, field_sql, tzname)
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return ('%s = %%s' % sql, tz_params + params)
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elif lookup_type in ('month', 'day', 'week_day'):
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return ('%s = %%s'
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% connection.ops.date_extract_sql(lookup_type, field_sql), params)
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elif lookup_type == 'isnull':
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assert value_annotation in (True, False), "Invalid value_annotation for isnull"
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return ('%s IS %sNULL' % (field_sql, ('' if value_annotation else 'NOT ')), ())
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elif lookup_type == 'search':
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return (connection.ops.fulltext_search_sql(field_sql), params)
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elif lookup_type in ('regex', 'iregex'):
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return connection.ops.regex_lookup(lookup_type) % (field_sql, cast_sql), params
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raise TypeError('Invalid lookup_type: %r' % lookup_type)
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def sql_for_columns(self, data, qn, connection, internal_type=None):
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"""
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Returns the SQL fragment used for the left-hand side of a column
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constraint (for example, the "T1.foo" portion in the clause
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"WHERE ... T1.foo = 6") and a list of parameters.
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"""
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table_alias, name, db_type = data
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if table_alias:
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lhs = '%s.%s' % (qn(table_alias), qn(name))
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else:
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lhs = qn(name)
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return connection.ops.field_cast_sql(db_type, internal_type) % lhs
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def relabel_aliases(self, change_map):
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"""
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Relabels the alias values of any children. 'change_map' is a dictionary
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mapping old (current) alias values to the new values.
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"""
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for pos, child in enumerate(self.children):
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if hasattr(child, 'relabel_aliases'):
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# For example another WhereNode
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child.relabel_aliases(change_map)
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elif isinstance(child, (list, tuple)):
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# tuple starting with Constraint
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child = (child[0].relabeled_clone(change_map),) + child[1:]
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if hasattr(child[3], 'relabeled_clone'):
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child = (child[0], child[1], child[2]) + (
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child[3].relabeled_clone(change_map),)
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self.children[pos] = child
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def clone(self):
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"""
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Creates a clone of the tree. Must only be called on root nodes (nodes
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with empty subtree_parents). Childs must be either (Contraint, lookup,
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value) tuples, or objects supporting .clone().
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"""
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clone = self.__class__._new_instance(
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children=[], connector=self.connector, negated=self.negated)
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for child in self.children:
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if hasattr(child, 'clone'):
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clone.children.append(child.clone())
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else:
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clone.children.append(child)
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return clone
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class EmptyWhere(WhereNode):
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def add(self, data, connector):
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return
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def as_sql(self, qn=None, connection=None):
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raise EmptyResultSet
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class EverythingNode(object):
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"""
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A node that matches everything.
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"""
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def as_sql(self, qn=None, connection=None):
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return '', []
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class NothingNode(object):
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"""
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A node that matches nothing.
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"""
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def as_sql(self, qn=None, connection=None):
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raise EmptyResultSet
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class ExtraWhere(object):
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def __init__(self, sqls, params):
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self.sqls = sqls
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self.params = params
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def as_sql(self, qn=None, connection=None):
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sqls = ["(%s)" % sql for sql in self.sqls]
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return " AND ".join(sqls), list(self.params or ())
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class Constraint(object):
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"""
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An object that can be passed to WhereNode.add() and knows how to
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pre-process itself prior to including in the WhereNode.
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"""
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def __init__(self, alias, col, field):
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self.alias, self.col, self.field = alias, col, field
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def prepare(self, lookup_type, value):
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if self.field:
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return self.field.get_prep_lookup(lookup_type, value)
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return value
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def process(self, lookup_type, value, connection):
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"""
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Returns a tuple of data suitable for inclusion in a WhereNode
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instance.
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"""
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# Because of circular imports, we need to import this here.
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from django.db.models.base import ObjectDoesNotExist
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try:
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if self.field:
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params = self.field.get_db_prep_lookup(lookup_type, value,
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connection=connection, prepared=True)
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db_type = self.field.db_type(connection=connection)
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else:
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# This branch is used at times when we add a comparison to NULL
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# (we don't really want to waste time looking up the associated
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# field object at the calling location).
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params = Field().get_db_prep_lookup(lookup_type, value,
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connection=connection, prepared=True)
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db_type = None
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except ObjectDoesNotExist:
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raise EmptyShortCircuit
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return (self.alias, self.col, db_type), params
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def relabeled_clone(self, change_map):
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if self.alias not in change_map:
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return self
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else:
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new = Empty()
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new.__class__ = self.__class__
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new.alias, new.col, new.field = change_map[self.alias], self.col, self.field
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return new
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class SubqueryConstraint(object):
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def __init__(self, alias, columns, targets, query_object):
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self.alias = alias
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self.columns = columns
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self.targets = targets
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self.query_object = query_object
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def as_sql(self, qn, connection):
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query = self.query_object
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# QuerySet was sent
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if hasattr(query, 'values'):
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if query._db and connection.alias != query._db:
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raise ValueError("Can't do subqueries with queries on different DBs.")
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# Do not override already existing values.
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if not hasattr(query, 'field_names'):
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query = query.values(*self.targets)
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else:
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query = query._clone()
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query = query.query
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query.clear_ordering(True)
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query_compiler = query.get_compiler(connection=connection)
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return query_compiler.as_subquery_condition(self.alias, self.columns, qn)
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def relabel_aliases(self, change_map):
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self.alias = change_map.get(self.alias, self.alias)
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def clone(self):
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return self.__class__(
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self.alias, self.columns, self.targets,
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self.query_object)
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