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query.py
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213 lines (177 loc) · 7.34 KB
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# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Helps build SQL for complex Spanner queries."""
import abc
from typing import Any, Dict, Generic, Iterable, List, Sequence, Tuple, Type, TypeVar
from spanner_orm import condition
from spanner_orm import error
ResultType = TypeVar('ResultType')
class SpannerQuery(abc.ABC, Generic[ResultType]):
"""Helps build SQL for complex Spanner queries."""
def __init__(self, model: Type[Any],
conditions: Iterable[condition.Condition]):
self.param_offset = 0
self._model = model
self._conditions = conditions
self._sql = ''
self._parameters = {}
self._types = {}
self._build()
def _next_param_index(self) -> int:
return self.param_offset + len(self._parameters)
def parameters(self) -> Dict[str, Any]:
return self._parameters
def sql(self) -> str:
return self._sql
def types(self) -> Dict[str, Any]:
return self._types
@abc.abstractmethod
def process_results(self, results: List[Sequence[Any]]) -> ResultType:
pass
def _segments(self,
segment_type: condition.Segment) -> List[condition.Condition]:
segments = [
condition for condition in self._conditions
if condition.segment() == segment_type
]
for segment in segments:
segment.bind(self._model)
return segments
def _build(self) -> None:
"""Builds the Spanner query from the given model and conditions."""
segment_builders = [
self._select, self._from, self._where, self._order, self._limit
]
self._sql, self._parameters, self._types = '', {}, {}
for segment_builder in segment_builders:
segment_sql, segment_parameters, segment_types = segment_builder()
self._sql += segment_sql
self._parameters.update(segment_parameters)
self._types.update(segment_types)
@abc.abstractmethod
def _select(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
"""Processes the SELECT segment of the SQL query."""
pass
def _from(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
"""Processes the FROM segment of the SQL query."""
froms = self._segments(condition.Segment.FROM)
index_sql = ''
if froms:
if len(froms) != 1:
raise error.SpannerError('Only one index can be specified')
force_index = froms[0]
index_sql = force_index.sql()
sql = ' FROM {}{}'.format(self._model.table, index_sql)
return (sql, {}, {})
def _where(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
"""Processes the WHERE segment of the SQL query."""
sql, sql_parts, parameters, types = '', [], {}, {}
wheres = self._segments(condition.Segment.WHERE)
for where in wheres:
where.suffix = str(self._next_param_index() + len(parameters))
sql_parts.append(where.sql())
parameters.update(where.params())
types.update(where.types())
if sql_parts:
sql = ' WHERE {}'.format(' AND '.join(sql_parts))
return (sql, parameters, types)
def _order(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
"""Processes the ORDER BY segment of the SQL query."""
sql, parameters, types = '', {}, {}
orders = self._segments(condition.Segment.ORDER_BY)
if orders:
if len(orders) != 1:
raise error.SpannerError('Only one order condition may be specified')
order = orders[0]
order.suffix = str(self._next_param_index())
sql = ' ' + order.sql()
parameters = order.params()
types = order.types()
return (sql, parameters, types)
def _limit(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
"""Processes the LIMIT segment of the SQL query."""
sql, parameters, types = '', {}, {}
limits = self._segments(condition.Segment.LIMIT)
if limits:
if len(limits) != 1:
raise error.SpannerError('Only one limit condition may be specified')
limit = limits[0]
limit.suffix = str(self._next_param_index())
sql = ' ' + limit.sql()
parameters = limit.params()
types = limit.types()
return (sql, parameters, types)
class CountQuery(SpannerQuery[int]):
"""Handles COUNT Spanner queries."""
def __init__(self, model: Type[Any],
conditions: Iterable[condition.Condition]):
super().__init__(model, conditions)
for c in conditions:
if c.segment() not in [condition.Segment.WHERE, condition.Segment.FROM]:
raise error.SpannerError('Only conditions that affect the WHERE or '
'FROM clauses are allowed for count queries')
def _select(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
return ('SELECT COUNT(*)', {}, {})
def process_results(self, results: List[Sequence[Any]]) -> int:
return int(results[0][0])
class SelectQuery(SpannerQuery[List[Type[Any]]]):
"""Handles SELECT Spanner queries."""
def __init__(self, model: Type[Any],
conditions: Iterable[condition.Condition]):
self._model = model
self._conditions = conditions
self._joins = self._segments(condition.Segment.JOIN)
self._subqueries = [
_SelectSubQuery(join.destination, join.conditions)
for join in self._joins
if isinstance(join, condition.IncludesCondition)
]
super().__init__(model, conditions)
def _select_prefix(self) -> str:
return 'SELECT'
def _select(self) -> Tuple[str, Dict[str, Any], Dict[str, Any]]:
parameters, types = {}, {}
columns = [
'{alias}.{column}'.format(
alias=self._model.column_prefix, column=column)
for column in self._model.columns
]
for subquery in self._subqueries:
subquery.param_offset = self._next_param_index()
columns.append('ARRAY({subquery})'.format(subquery=subquery.sql()))
parameters.update(subquery.parameters())
types.update(subquery.types())
return ('{prefix} {columns}'.format(
prefix=self._select_prefix(),
columns=', '.join(columns)), parameters, types)
def process_results(self, results: List[Sequence[Any]]) -> List[Type[Any]]:
return [self._process_row(result) for result in results]
def _process_row(self, row: Sequence[Any]) -> Type[Any]:
"""Parses a row of results from a Spanner query based on the conditions."""
values = dict(zip(self._model.columns, row))
join_values = row[len(self._model.columns):]
for join, subquery, join_value in zip(self._joins, self._subqueries,
join_values):
models = subquery.process_results(join_value)
if join.single:
if len(models) > 1:
raise error.SpannerError(
'Multiple objects returned for relationship marked as single')
values[join.relation_name] = models[0] if models else None
else:
values[join.relation_name] = models
return self._model(values, persisted=True)
class _SelectSubQuery(SelectQuery):
def _select_prefix(self) -> str:
return 'SELECT AS STRUCT'