RE: Postgres index usage - Mailing list pgsql-performance

From Dirschel, Steve
Subject RE: Postgres index usage
Date
Msg-id BL0PR03MB4001D1B44A9585FD68C252F0FAB82@BL0PR03MB4001.namprd03.prod.outlook.com
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In response to Postgres index usage  ("Dirschel, Steve" <steve.dirschel@thomsonreuters.com>)
List pgsql-performance

Didn’t mention-  this is Aurora Postgres version 14.6 if that matters for my question.  Thanks

 

From: Dirschel, Steve <steve.dirschel@thomsonreuters.com>
Sent: Wednesday, August 7, 2024 12:06 PM
To: pgsql-performance@lists.postgresql.org
Subject: Postgres index usage

 

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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