What should be checked when changing value of track_activity_query_size parameter?

Question

When using Aurora PostgreSQL, to show the full text of SQL queries on the Performance Insights, a customer plans to change value of track_activity_query_size from 4kb (default) to 20kb. But, the customer is concerned that this change could cause performance issue and they want to know what points they should check after changing this parameter (e.g. CPU usage rate, disk I/O rate, cache hit rate, etc.).
If you have any suggestion or idea, could you advise me?

Accepted Answer

Since the full SQL statements are cached in memory, memory usage may increase and affect the cache hit rate. As documented below, pg_stat_statements.max * track_activity_query_size bytes additional shared memory is required.

https://www.postgresql.jp/document/9.0/html/pgstatstatements.html

You may have to check the  change in cache hit rate of the database and monitor for increasing wait events using RDS Performance  Insights.

What should be checked when changing value of track_activity_query_size parameter?

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