PostgreSQL查看索引的使用情况

--==========================================
--查看索引的使用情况
--索引在重建或删除新建时sys.dm_db_index_usage_stats中相关的数据会被清除
--索引在重整是不会清除sys.dm_db_index_usage_stats的数据
SELECT  DB_NAME(ixu.database_id) DataBase_Name ,
        OBJECT_NAME(ixu.object_id) Table_Name ,
        ix.name Index_Name ,
        ( SELECT    MAX(s.rows)
          FROM      sysindexes s
          WHERE     s.id = ixu.object_id
        ) AS Table_Rows ,
        STATS_DATE(ixu.object_id, ixu.index_id) AS statistic_time ,
        ixu.user_updates ,
        ixu.last_user_update ,
        ixu.last_user_seek ,
        ixu.user_seeks ,
        ixu.last_user_scan ,
        ixu.user_scans ,
        ixu.last_user_lookup ,
        ixu.user_lookups ,
        ixu.user_updates / ( ISNULL(ixu.user_seeks, 0) + ISNULL(ixu.user_scans,
                                                              0) + 1 ) AS UseRate
FROM    sys.dm_db_index_usage_stats ixu
        INNER JOIN sys.indexes ix
        ON ixu.object_id = ix.object_id
           AND ixu.index_id = ix.index_id
        INNER JOIN sys.objects ob
        ON ixu.object_id = ob.object_id
WHERE   ob.type = 'U'
        AND ob.is_ms_shipped = 0
        AND ixu.database_id = DB_ID()
--AND ix.object_id=OBJECT_ID('TableName')

存放索引详细信息的表

data_name=# \d+ pg_stat_user_indexes;
           View "pg_catalog.pg_stat_user_indexes"
    Column     |  Type  | Modifiers | Storage | Description 
---------------+--------+-----------+---------+-------------
 relid         | oid |           | plain | 
 indexrelid    | oid |           | plain | 
 schemaname    | name |           | plain | 
 relname       | name |           | plain | 
 indexrelname  | name |           | plain | 
 idx_scan      | bigint |           | plain | 
 idx_tup_read  | bigint |           | plain | 
 idx_tup_fetch | bigint |           | plain | 
View definition:
 SELECT pg_stat_all_indexes.relid,
    pg_stat_all_indexes.indexrelid,
    pg_stat_all_indexes.schemaname,
    pg_stat_all_indexes.relname,
    pg_stat_all_indexes.indexrelname,
    pg_stat_all_indexes.idx_scan,
    pg_stat_all_indexes.idx_tup_read,
    pg_stat_all_indexes.idx_tup_fetch
   FROM pg_stat_all_indexes
  WHERE (pg_stat_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND pg_stat_all_indexes.schemaname !~ '^pg_toast'::text;

通过这个表查看某个表的索引使用情况易如反掌了。

示例一、查看所有表的索引的使用情况

select relname, indexrelname, idx_scan, idx_tup_read, idx_tup_fetch from pg_stat_user_indexes order by idx_scan asc, idx_tup_read asc, idx_tup_fetch asc;

示例二、查看某个表的索引使用情况

select relname, indexrelname, idx_scan, idx_tup_read, idx_tup_fetch from pg_stat_user_indexes where relname = table_name order by idx_scan asc, idx_tup_read asc, idx_tup_fetch asc;