added postgres_blocked_queries.sql

sql/postgres_blocked_queries.sql

@@ -0,0 +1,30 @@
+--
+--  Author: Hari Sekhon
+--  Date: 2020-08-05 18:53:54 +0100 (Wed, 05 Aug 2020)
+--
+--  vim:ts=2:sts=2:sw=2:et:filetype=sql
+--
+--  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
+--
+
+-- Lists PostgreSQL queries blocked along with the pids of those holding the locks blocking them
+--
+-- Requires PostgreSQL >= 9.6
+--
+-- Tested on PostgreSQL 12.3
+
+SELECT
+  pid,
+  user,
+  pg_blocking_pids(pid) AS blocked_by_pids,
+  query AS blocked_query
+FROM
+  pg_stat_activity
+WHERE
+  cardinality(pg_blocking_pids(pid)) > 0;