Postgres index usage - Mailing list pgsql-performance

From Dirschel, Steve
Subject Postgres index usage
Date
Msg-id BL0PR03MB4001C72C153C481533CBFCDAFAB82@BL0PR03MB4001.namprd03.prod.outlook.com
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In response to Re: "not related" code blocks for removal of dead rows when using vacuum and this kills the performance  (Lars Aksel Opsahl <Lars.Opsahl@nibio.no>)
Responses RE: Postgres index usage
Re: Postgres index usage
Re: Postgres index usage
List pgsql-performance

I’ve found multiple postings out there saying you can query pg_stat_all_indexes and look at idx_scan to know if an index has been used by queries.  I want to be 100% sure I can rely on that table/column to know if an index has never been used.

 

I queried that table for a specific index and idx_scan is 0.  I queried pg_statio_all_indexes and can see idx_blks_read and idx_blks_hit have numbers in there.  If the index is not being used then what it causing idx_blks_read and idx_blks_hit to increase over time?  I’m wondering if those increase due to DML on the table.  Could anyone please confirm I can rely on pg_stat_all_index.idx_scan to know if queries are using an index and the increases over time in idx_blks_read and idx_blks_hit in pg_statio_all_indexes would be from DML (or possibly vacuum or other things)?

 

Thanks in advance.

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