Over a short period of time, this is my incoming federation activity for new comments. pg_stat_statements output being show. It is interesting to note these two INSERT statements on comments differ only in the DEFAULT value of language column. Also note the average execution times is way higher (4.3 vs. 1.28) when the language value is set, I assume due to INDEX updates on the column? Or possibly a TRIGGER?
About half of the comments coming in from other servers have default value.
WRITES are heavy, even if it is an INDEX that has to be revised. So INSERT and UPDATE statements are important to scrutinize.
I got burned by thinking it was seconds weeks back. Documentation:
mean_plan_time double precision
Mean time spent planning the statement, in milliseconds (if pg_stat_statements.track_planning is enabled, otherwise zero)