added postgres_tables_index_usage.sql

sql/postgres_tables_index_usage.sql

@@ -0,0 +1,29 @@
+--
+--  Author: Hari Sekhon
+--  Date: 2020-08-05 15:08:23 +0100 (Wed, 05 Aug 2020)
+--
+--  vim:ts=4:sts=4:sw=4:et
+--
+--  https://github.com/harisekhon/bash-tools
+--
+--  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
+--
+--  https://www.linkedin.com/in/harisekhon
+--
+
+-- PostgreSQL % of times indexes are used on tables by table size descending (might want to tweak to list by % descending)
+
+SELECT
+  relname AS table,
+  idx_scan / (seq_scan + idx_scan) * 100 AS percent_of_times_index_used,
+  n_live_tup AS rows_in_table
+FROM
+  pg_stat_user_tables
+WHERE
+  seq_scan + idx_scan > 0
+ORDER BY
+  n_live_tup,
+  percent_of_times_index_used
+DESC;