我有一张表上的一个索引,我想暂时禁用它,但是我找不到任何文件说明它是否可能被禁用。
原因:我有一个索引,可能会在与其设计用于加速查询无关的查询中出现问题。这是一个新索引,自从引入它后整个系统似乎变得更慢了。我只想能够可靠地将其排除为罪犯,并且这似乎是最简单的方法,其他解决方案建议以及更好的问题建议也欢迎。
我有一张表上的一个索引,我想暂时禁用它,但是我找不到任何文件说明它是否可能被禁用。
原因:我有一个索引,可能会在与其设计用于加速查询无关的查询中出现问题。这是一个新索引,自从引入它后整个系统似乎变得更慢了。我只想能够可靠地将其排除为罪犯,并且这似乎是最简单的方法,其他解决方案建议以及更好的问题建议也欢迎。
您可以操纵系统目录以禁用索引:
update pg_index set indisvalid = false where indexrelid = 'test_pkey'::regclass
这意味着该索引不会用于查询,但仍将被更新。它是用于并发索引构建的标志之一。请注意,我只进行了快速测试以查看索引是否仍在更新,买方自负。
begin;
drop index foo_ndx;
explain analyze select * from foo;
rollback;
我认为没有办法只禁用其中一个索引,但你可以在事务中执行此操作,以使从中恢复变得非常简单。您还可以禁用 indexscan 以禁用所有索引。
此外,请确保在查询上执行 explain analyze
。
ALTER TABLE foo DROP CONSTRAINT foo_pkey;
而不是 DROP INDEX foo_ndex;
。) - cdhowiefoo_ndx
上获得一个 ACCESS EXCLUSIVE
锁,那么这会对其他并发查询产生什么影响呢?它们会使用或不使用该索引,还是会被阻塞直到该事务完成? - Steve Kehlet我已经创建(并审核)了一个函数,可以应对各种情况。你需要小心使用它,但它确实有效。
CREATE OR REPLACE PROCEDURE global.enable_indexes(
IN schema_name TEXT
, IN table_name TEXT
, IN index_name TEXT
, IN enable_use BOOLEAN
, IN enable_updates BOOLEAN
, IN skip_essentials BOOLEAN DEFAULT TRUE
) AS
$$
DECLARE
each_record RECORD;
BEGIN
/*
USAGE:
schema_name:
- filters down by schema name
- if NULL then does not filter
table_name:
- filters down by table name (careful - not schema qualified)
- if NULL then does not filter
index_name:
- filters down by index name (careful - not schema qualified)
- if NULL then does not filter
enable_use:
- This SETs the index as being available for use.
- If enable_updates is FALSE, then automatically FALSE
enable_updates:
- This SETs the index to be updated (which doesn't imply that it is enabled for use)
- When this was previously FALSE for the given index, then when setting to true will also trigger a rebuild of the index
skip_essentials:
- When this is true, PRIMARY and UNIQUE indexes will not be included in the scope (no changes).
- Optional
*/
IF array_replace(ARRAY[schema_name, table_name, index_name], NULL, '') <@ ARRAY[''] THEN
RAISE EXCEPTION 'Error: Must specify at least one of schema_name | table_name | index_name';
END IF;
IF enable_updates IS FALSE THEN
enable_use := FALSE;
RAISE INFO 'FYI: Because enable_updates is FALSE, then likewise enable_use must be as well';
END IF;
FOR each_record IN
select
indexrelid
, (schemaname||'.'||indexname) as index_name
, indisvalid
, indisready
, (schemaname||'.'||tablename) as table_name
, (CASE WHEN indisready IS FALSE and enable_use IS TRUE AND enable_updates IS TRUE THEN TRUE ELSE FALSE END) as needs_rebuilding
FROM pg_indexes, pg_index
WHERE
indexrelid = (schemaname||'.'||indexname)::regclass
AND case when schema_name <> '' THEN schemaname = schema_name ELSE TRUE END
AND case when table_name <> '' THEN tablename = table_name ELSE TRUE END
AND case when index_name <> '' THEN indexname = index_name ELSE TRUE END
AND case when true THEN least(indisprimary, indisunique) = FALSE ELSE TRUE END
AND case when skip_essentials THEN least(indisprimary, indisunique) = FALSE ELSE TRUE END
LOOP
BEGIN
RAISE INFO 'Set index % to have use % and updates %.'
, each_record.index_name
, (case when each_record.indisvalid AND enable_use THEN 'enabled (not changed)' WHEN NOT each_record.indisvalid AND enable_use THEN 'enabled (changed)' else 'disabled' END)
, (case when each_record.indisready AND enable_updates THEN 'enabled (not changed)' WHEN NOT each_record.indisready AND enable_updates THEN 'enabled (changed)' else 'disabled' END)
;
UPDATE pg_index
SET
indisvalid = enable_use
, indisready = enable_updates
WHERE
indexrelid = each_record.indexrelid
;
IF each_record.needs_rebuilding THEN
RAISE INFO '... Reindexing and Analyzing %', each_record.index_name;
EXECUTE format('REINDEX INDEX %1$s; ANALYZE %2$s;', each_record.index_name, each_record.table_name);
END IF;
COMMIT;
END;
END LOOP;
END
$$
LANGUAGE plpgsql
;
\d tags
没有显示索引(这是在运行call enable_indexes('', 'tags', '', true, true, false);
和call enable_indexes('', 'tags', '', false, false, false);
之前)。我还将pg_catalog.pg_class.relhasindex
的值设置为f
,其中relname ='tags'
。我已经更新了relhasindex ='t'
,但tags
上的索引仍未显示。现在我正在运行reindex table tags
。 - portonANALYZE
而不是每个索引执行一次。 - Sergey Nevmerzhitsky
indisready
设置为false,会禁用更新。详情请参考:http://www.postgresql.org/docs/current/static/catalog-pg-index.html。 - araqnid