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# coding: utf-8 |
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from __future__ import unicode_literals |
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import datetime |
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from decimal import Decimal |
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from hashlib import sha1 |
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from time import time |
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from uuid import UUID |
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from django.db import connections |
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from django.db.models.sql import Query |
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from django.db.models.sql.where import ExtraWhere, SubqueryConstraint |
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from django.utils.module_loading import import_string |
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from django.utils.six import text_type, binary_type |
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from .settings import cachalot_settings |
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from .signals import post_invalidation |
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from .transaction import AtomicCache |
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class UncachableQuery(Exception): |
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pass |
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CACHABLE_PARAM_TYPES = { |
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bool, int, float, Decimal, binary_type, text_type, type(None), |
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datetime.date, datetime.time, datetime.datetime, datetime.timedelta, UUID, |
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} |
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try: |
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from psycopg2.extras import ( |
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NumericRange, DateRange, DateTimeRange, DateTimeTZRange, Inet) |
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except ImportError: |
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pass |
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else: |
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CACHABLE_PARAM_TYPES.update(( |
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NumericRange, DateRange, DateTimeRange, DateTimeTZRange, Inet)) |
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def check_parameter_types(params): |
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for p in params: |
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cl = p.__class__ |
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if cl not in CACHABLE_PARAM_TYPES: |
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if cl is list or cl is tuple: |
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check_parameter_types(p) |
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elif cl is dict: |
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check_parameter_types(p.items()) |
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else: |
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raise UncachableQuery |
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def get_query_cache_key(compiler): |
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""" |
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Generates a cache key from a SQLCompiler. |
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This cache key is specific to the SQL query and its context |
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(which database is used). The same query in the same context |
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(= the same database) must generate the same cache key. |
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:arg compiler: A SQLCompiler that will generate the SQL query |
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:type compiler: django.db.models.sql.compiler.SQLCompiler |
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:return: A cache key |
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:rtype: str |
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""" |
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sql, params = compiler.as_sql() |
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check_parameter_types(params) |
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cache_key = '%s:%s:%s' % (compiler.using, sql, params) |
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return sha1(cache_key.encode('utf-8')).hexdigest() |
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def get_table_cache_key(db_alias, table): |
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""" |
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Generates a cache key from a SQL table. |
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:arg db_alias: Alias of the used database |
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:type db_alias: str or unicode |
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:arg table: Name of the SQL table |
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:type table: str or unicode |
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:return: A cache key |
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:rtype: str |
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""" |
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cache_key = '%s:%s' % (db_alias, table) |
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return sha1(cache_key.encode('utf-8')).hexdigest() |
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def _get_query_cache_key(compiler): |
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return import_string(cachalot_settings.CACHALOT_QUERY_KEYGEN)(compiler) |
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def _get_table_cache_key(db_alias, table): |
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return import_string(cachalot_settings.CACHALOT_TABLE_KEYGEN)(db_alias, table) |
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def _get_tables_from_sql(connection, lowercased_sql): |
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return [t for t in connection.introspection.django_table_names() |
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if t in lowercased_sql] |
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def _find_subqueries(children): |
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for child in children: |
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if child.__class__ is SubqueryConstraint: |
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if child.query_object.__class__ is Query: |
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yield child.query_object |
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else: |
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yield child.query_object.query |
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else: |
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rhs = None |
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if hasattr(child, 'rhs'): |
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rhs = child.rhs |
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elif child.__class__ is tuple: |
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rhs = child[-1] |
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if rhs.__class__ is Query: |
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yield rhs |
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elif hasattr(rhs, 'query'): |
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yield rhs.query |
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if hasattr(child, 'children'): |
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for grand_child in _find_subqueries(child.children): |
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yield grand_child |
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def _get_tables(query, db_alias): |
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if '?' in query.order_by and not cachalot_settings.CACHALOT_CACHE_RANDOM: |
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raise UncachableQuery |
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tables = set(query.table_map) |
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tables.add(query.get_meta().db_table) |
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subquery_constraints = _find_subqueries(query.where.children |
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+ query.having.children) |
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for subquery in subquery_constraints: |
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tables.update(_get_tables(subquery, db_alias)) |
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if query.extra_select or hasattr(query, 'subquery') \ |
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or any(c.__class__ is ExtraWhere for c in query.where.children): |
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sql = query.get_compiler(db_alias).as_sql()[0].lower() |
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additional_tables = _get_tables_from_sql(connections[db_alias], sql) |
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tables.update(additional_tables) |
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whitelist = cachalot_settings.CACHALOT_ONLY_CACHABLE_TABLES |
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blacklist = cachalot_settings.CACHALOT_UNCACHABLE_TABLES |
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if (whitelist and not tables.issubset(whitelist)) \ |
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or not tables.isdisjoint(blacklist): |
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raise UncachableQuery |
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return tables |
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def _get_table_cache_keys(compiler): |
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db_alias = compiler.using |
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tables = _get_tables(compiler.query, db_alias) |
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return [_get_table_cache_key(db_alias, t) for t in tables] |
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def _invalidate_tables(cache, db_alias, tables): |
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now = time() |
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d = {} |
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for table in tables: |
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d[_get_table_cache_key(db_alias, table)] = now |
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cache.set_many(d, None) |
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if isinstance(cache, AtomicCache): |
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cache.to_be_invalidated.update(tables) |
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def _invalidate_table(cache, db_alias, table): |
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cache.set(_get_table_cache_key(db_alias, table), time(), None) |
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if isinstance(cache, AtomicCache): |
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cache.to_be_invalidated.add(table) |
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else: |
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post_invalidation.send(table, db_alias=db_alias) |
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noripyt /
django-cachalot
