193 lines
6.9 KiB
Python
193 lines
6.9 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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import datetime
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from django.utils import tree
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from django.db import connection
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from django.db.models.fields import Field
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from django.db.models.query_utils import QueryWrapper
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from datastructures import EmptyResultSet, FullResultSet
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# Connection types
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AND = 'AND'
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OR = 'OR'
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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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The children in this tree are usually either Q-like objects or lists of
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[table_alias, field_name, db_type, lookup_type, value_annotation,
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params]. However, a child could also be any class with as_sql() and
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relabel_aliases() methods.
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"""
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default = AND
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def add(self, data, connector):
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"""
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Add a node to the where-tree. If the data is a list or tuple, it is
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expected to be of the form (alias, col_name, field_obj, lookup_type,
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value), which is then slightly munged before being stored (to avoid
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storing any reference to field objects). Otherwise, the 'data' is
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stored unchanged and can be anything with an 'as_sql()' method.
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"""
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if not isinstance(data, (list, tuple)):
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super(WhereNode, self).add(data, connector)
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return
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alias, col, field, lookup_type, value = data
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if field:
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params = field.get_db_prep_lookup(lookup_type, value)
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db_type = field.db_type()
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else:
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# This is possible when we add a comparison to NULL sometimes (we
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# don't really need to waste time looking up the associated field
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# object).
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params = Field().get_db_prep_lookup(lookup_type, value)
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db_type = None
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if isinstance(value, datetime.datetime):
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annotation = datetime.datetime
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else:
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annotation = bool(value)
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super(WhereNode, self).add((alias, col, db_type, lookup_type,
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annotation, params), connector)
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def as_sql(self, qn=None):
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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 None, None if this node is empty.
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If 'node' is provided, that is the root of the SQL generation
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(generally not needed except by the internal implementation for
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recursion).
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"""
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if not qn:
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qn = connection.ops.quote_name
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if not self.children:
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return None, []
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result = []
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result_params = []
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empty = True
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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)
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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)
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except EmptyResultSet:
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if self.connector == AND and not self.negated:
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# We can bail out early in this particular case (only).
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raise
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elif self.negated:
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empty = False
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continue
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except FullResultSet:
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if self.connector == OR:
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if self.negated:
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empty = True
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break
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# We match everything. No need for any constraints.
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return '', []
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if self.negated:
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empty = True
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continue
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empty = False
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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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if empty:
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raise EmptyResultSet
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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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sql_string = 'NOT (%s)' % sql_string
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elif len(self.children) != 1:
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sql_string = '(%s)' % sql_string
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return sql_string, result_params
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def make_atom(self, child, qn):
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"""
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Turn a tuple (table_alias, column_name, db_type, lookup_type,
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value_annot, params) into valid SQL.
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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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table_alias, name, db_type, lookup_type, value_annot, params = child
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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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field_sql = connection.ops.field_cast_sql(db_type) % lhs
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if value_annot is datetime.datetime:
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cast_sql = connection.ops.datetime_cast_sql()
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else:
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cast_sql = '%s'
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if isinstance(params, QueryWrapper):
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extra, params = params.data
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else:
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extra = ''
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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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extra)
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return (format % (field_sql,
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connection.operators[lookup_type] % cast_sql), params)
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if lookup_type == 'in':
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if not value_annot:
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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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return ('%s IN (%s)' % (field_sql, ', '.join(['%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 lookup_type in ('month', 'day'):
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return ('%s = %%s' % connection.ops.date_extract_sql(lookup_type,
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field_sql), params)
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elif lookup_type == 'isnull':
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return ('%s IS %sNULL' % (field_sql,
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(not value_annot and 'NOT ' or '')), ())
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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 relabel_aliases(self, change_map, node=None):
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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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if not node:
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node = self
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for pos, child in enumerate(node.children):
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if hasattr(child, 'relabel_aliases'):
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child.relabel_aliases(change_map)
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elif isinstance(child, tree.Node):
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self.relabel_aliases(change_map, child)
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else:
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if child[0] in change_map:
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node.children[pos] = (change_map[child[0]],) + child[1:]
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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):
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raise FullResultSet
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def relabel_aliases(self, change_map, node=None):
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return
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