Question

我在一张桌子上有一个我想要暂时禁用的索引，但是我找不到任何可以证明它有可能的文档。

原因：我有一个索引可能会导致与其设计加速的任何查询无关的查询出现问题。这是一个新的索引，整个系统自推出以来似乎较慢。我只是希望能够可靠地消除它作为罪魁祸首，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，也是受欢迎的。

Answer 1

您可以戳系统目录以禁用索引：

update pg_index set indisvalid = false where indexrelid = 'test_pkey'::regclass

这意味着索引不会用于查询，但仍会更新。它是用于并发索引构建的标志之一。请注意，我只是做了一个快速测试，看看索引是否似乎仍在更新，请注意。

Answer 2

begin;
drop index foo_ndx;
explain analyze select * from foo;
rollback;

我认为没有办法只禁用一个，尽管你可以在一个事务中执行此操作，以便从中恢复简单。您还可以禁用indexscan以禁用所有索引。

另外，请确保您对查询进行explain analyze。

Answer 3

我已经创建（并审查了）一个可以在多种情况下执行此操作的函数。您绝对需要小心，但是它确实可以工作。

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
;

是否有可能暂时禁用Postgres中的索引？

3 个答案: