mirror of
https://github.com/Hopiu/django-cachalot.git
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145 lines
4.4 KiB
Python
145 lines
4.4 KiB
Python
# coding: utf-8
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from __future__ import unicode_literals
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from collections import Iterable
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import re
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from django.core.cache import cache
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from django.db.models.query import EmptyResultSet
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from django.db.models.sql.compiler import (
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SQLCompiler, SQLAggregateCompiler, SQLDateCompiler, SQLDateTimeCompiler,
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SQLInsertCompiler, SQLUpdateCompiler, SQLDeleteCompiler)
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from django.db.models.sql.where import ExtraWhere
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COMPILERS = (SQLCompiler,
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SQLAggregateCompiler, SQLDateCompiler, SQLDateTimeCompiler,
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SQLInsertCompiler, SQLUpdateCompiler, SQLDeleteCompiler)
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WRITE_COMPILERS = (SQLInsertCompiler, SQLUpdateCompiler, SQLDeleteCompiler)
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READ_COMPILERS = [c for c in COMPILERS if c not in WRITE_COMPILERS]
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PATCHED = False
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MISS_VALUE = '[[The cache key was missed]]'
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def _get_tables(query):
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"""
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Returns a ``set`` of all database table names used by ``query``.
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"""
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tables = query.used_aliases.copy()
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tables.add(query.model._meta.db_table)
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tables.update(query.extra_tables)
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return tables
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def _get_tables_cache_keys(query):
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return ['%s_queries' % t for t in _get_tables(query)]
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def _update_tables_queries(query, cache_key):
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tables_cache_keys = _get_tables_cache_keys(query)
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tables_queries = cache.get_many(tables_cache_keys)
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for k in tables_cache_keys:
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queries = tables_queries.get(k, [])
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queries.append(cache_key)
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tables_queries[k] = queries
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cache.set_many(tables_queries)
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def _invalidate_tables(query):
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tables_cache_keys = _get_tables_cache_keys(query)
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tables_queries = cache.get_many(tables_cache_keys)
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queries = []
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for k in tables_cache_keys:
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queries.extend(tables_queries.get(k, []))
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cache.delete_many(queries)
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cache.delete_many(tables_cache_keys)
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COLUMN_RE = re.compile(r'^"(?P<table>[\w_]+)"\."(?P<column>[\w_]+)"$')
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def _has_extra_select_or_where(query):
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"""
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Returns True if ``query`` contains a ``QuerySet.extra`` with ``select``
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or ``where`` arguments.
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We also have to check for ``prefetch_related``, as it internally uses a
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``QuerySet.extra(select={'_prefetch_related_val_…': '"table"."column"'})``.
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For more details on how prefetch_related uses ``QuerySet.extra``, see:
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https://github.com/django/django/blob/1.6.7/django/db/models/fields/related.py#L553-L577
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"""
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# Checks if there’s an extra where
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if any(isinstance(child, ExtraWhere) for child in query.where.children):
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return True
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# Checks if there’s an extra select
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if query.extra_select and query.extra_select_mask is None:
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tables = _get_tables(query)
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# Checks if extra subqueries are something else than one or several
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# ``prefetch_related``.
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for subquery, params in query.extra_select.values():
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match = COLUMN_RE.match(subquery)
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return match is None or match.group('table') not in tables
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return False
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def _monkey_patch_orm_read():
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def patch_execute_sql(method):
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def inner(compiler, *args, **kwargs):
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if isinstance(compiler, WRITE_COMPILERS):
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return method(compiler, *args, **kwargs)
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query = compiler.query
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if _has_extra_select_or_where(query):
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return method(compiler, *args, **kwargs)
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try:
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cache_key = compiler.as_sql()
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except EmptyResultSet:
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return method(compiler, *args, **kwargs)
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result = cache.get(cache_key, MISS_VALUE)
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if result == MISS_VALUE:
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result = method(compiler, *args, **kwargs)
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if isinstance(result, Iterable) \
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and not isinstance(result, (tuple, list)):
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result = list(result)
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_update_tables_queries(query, cache_key)
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cache.set(cache_key, result)
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return result
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return inner
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for compiler in READ_COMPILERS:
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compiler.execute_sql = patch_execute_sql(compiler.execute_sql)
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def _monkey_patch_orm_write():
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def patch_execute_sql(method):
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def inner(compiler, *args, **kwargs):
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_invalidate_tables(compiler.query)
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return method(compiler, *args, **kwargs)
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return inner
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for compiler in WRITE_COMPILERS:
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compiler.execute_sql = patch_execute_sql(compiler.execute_sql)
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def monkey_patch_orm():
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global PATCHED
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_monkey_patch_orm_write()
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_monkey_patch_orm_read()
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PATCHED = True
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def is_patched():
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return PATCHED
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