85 lines
3.2 KiB
Python
85 lines
3.2 KiB
Python
from django.core.exceptions import FieldError
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from django.db.models.fields import FieldDoesNotExist
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from django.db.models.sql.constants import LOOKUP_SEP
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class SQLEvaluator(object):
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def __init__(self, expression, query, allow_joins=True):
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self.expression = expression
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self.opts = query.get_meta()
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self.cols = {}
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self.contains_aggregate = False
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self.expression.prepare(self, query, allow_joins)
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def prepare(self):
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return self
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def as_sql(self, qn, connection):
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return self.expression.evaluate(self, qn, connection)
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def relabel_aliases(self, change_map):
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for node, col in self.cols.items():
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self.cols[node] = (change_map.get(col[0], col[0]), col[1])
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#####################################################
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# Vistor methods for initial expression preparation #
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#####################################################
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def prepare_node(self, node, query, allow_joins):
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for child in node.children:
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if hasattr(child, 'prepare'):
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child.prepare(self, query, allow_joins)
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def prepare_leaf(self, node, query, allow_joins):
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if not allow_joins and LOOKUP_SEP in node.name:
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raise FieldError("Joined field references are not permitted in this query")
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field_list = node.name.split(LOOKUP_SEP)
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if (len(field_list) == 1 and
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node.name in query.aggregate_select.keys()):
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self.contains_aggregate = True
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self.cols[node] = query.aggregate_select[node.name]
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else:
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try:
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field, source, opts, join_list, last, _ = query.setup_joins(
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field_list, query.get_meta(),
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query.get_initial_alias(), False)
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col, _, join_list = query.trim_joins(source, join_list, last, False)
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self.cols[node] = (join_list[-1], col)
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except FieldDoesNotExist:
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raise FieldError("Cannot resolve keyword %r into field. "
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"Choices are: %s" % (self.name,
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[f.name for f in self.opts.fields]))
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##################################################
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# Vistor methods for final expression evaluation #
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##################################################
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def evaluate_node(self, node, qn, connection):
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expressions = []
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expression_params = []
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for child in node.children:
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if hasattr(child, 'evaluate'):
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sql, params = child.evaluate(self, qn, connection)
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else:
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sql, params = '%s', (child,)
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if len(getattr(child, 'children', [])) > 1:
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format = '(%s)'
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else:
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format = '%s'
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if sql:
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expressions.append(format % sql)
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expression_params.extend(params)
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return connection.ops.combine_expression(node.connector, expressions), expression_params
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def evaluate_leaf(self, node, qn, connection):
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col = self.cols[node]
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if hasattr(col, 'as_sql'):
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return col.as_sql(qn, connection), ()
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else:
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return '%s.%s' % (qn(col[0]), qn(col[1])), ()
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