98 lines
3.4 KiB
Python
98 lines
3.4 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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#
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import operator
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from sqlalchemy import and_
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from sqlalchemy import asc
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from sqlalchemy import desc
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from sqlalchemy import not_
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from sqlalchemy import or_
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class QueryTransformer(object):
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operators = {"=": operator.eq,
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"<": operator.lt,
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">": operator.gt,
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"<=": operator.le,
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"=<": operator.le,
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">=": operator.ge,
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"=>": operator.ge,
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"!=": operator.ne,
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"in": lambda field_name, values: field_name.in_(values),
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"=~": lambda field, value: field.op("regexp")(value)}
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# operators which are differs for different dialects
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dialect_operators = {'postgresql': {'=~': (lambda field, value:
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field.op("~")(value))}}
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complex_operators = {"or": or_,
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"and": and_,
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"not": not_}
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ordering_functions = {"asc": asc,
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"desc": desc}
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def __init__(self, table, query, dialect='mysql'):
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self.table = table
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self.query = query
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self.dialect_name = dialect
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def _get_operator(self, op):
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return (self.dialect_operators.get(self.dialect_name, {}).get(op)
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or self.operators[op])
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def _handle_complex_op(self, complex_op, nodes):
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op = self.complex_operators[complex_op]
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if op == not_:
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nodes = [nodes]
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element_list = []
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for node in nodes:
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element = self._transform(node)
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element_list.append(element)
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return op(*element_list)
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def _handle_simple_op(self, simple_op, nodes):
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op = self._get_operator(simple_op)
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field_name, value = list(nodes.items())[0]
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return op(getattr(self.table, field_name), value)
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def _transform(self, sub_tree):
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operator, nodes = list(sub_tree.items())[0]
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if operator in self.complex_operators:
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return self._handle_complex_op(operator, nodes)
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else:
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return self._handle_simple_op(operator, nodes)
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def apply_filter(self, expression_tree):
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condition = self._transform(expression_tree)
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self.query = self.query.filter(condition)
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def apply_options(self, orderby, limit):
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self._apply_order_by(orderby)
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if limit is not None:
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self.query = self.query.limit(limit)
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def _apply_order_by(self, orderby):
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if orderby is not None:
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for field in orderby:
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attr, order = list(field.items())[0]
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ordering_function = self.ordering_functions[order]
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self.query = self.query.order_by(ordering_function(
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getattr(self.table, attr)))
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else:
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self.query = self.query.order_by(desc(self.table.timestamp))
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def get_query(self):
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return self.query
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