postgres_indexes_cache_hit_ratio.sql

--
--  Author: Hari Sekhon
--  Date: 2020-08-05 15:28:12 +0100 (Wed, 05 Aug 2020)
--
--  vim:ts=4:sts=4:sw=4:et:filetype=sql
--
--  https://github.com/HariSekhon/SQL-scripts
--
--  License: see accompanying Hari Sekhon LICENSE file
--
--  If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback to help steer this or other code I publish
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--  https://www.linkedin.com/in/HariSekhon
--

-- PostgreSQL Indexes Cache-hit Ratio
--
-- should be closer to 1, eg. 0.99
--
-- Tested on PostgreSQL 8.4, 9.x, 10.x, 11.x, 12.x, 13.0

SELECT
    SUM(idx_blks_read) AS idx_blks_read,
    SUM(idx_blks_hit)  AS idx_blks_hit,
             SUM(idx_blks_hit) /
    GREATEST(SUM(idx_blks_hit) + SUM(idx_blks_read), 1)::float
                AS ratio
FROM
    pg_statio_user_indexes;