Thanks for the excellent extension. I want to add 5 more fields to satisfy the following requirements.
int subplan; /* No. of subplan in this query */ int subquery; /* No. of subquery */ int joincnt; /* How many relations are joined */ bool hasagg; /* if we have agg function in this query */ bool hasgroup; /* has group clause */ 1. Usually I want to check total_exec_time / rows to see if the query is missing index, however aggregation/groupby case makes this rule doesn't work. so hasagg/hasgroup should be a good rule to filter out these queries. 2. subplan is also a important clue to find out the query to turning. when we check the slow queries with pg_stat_statements, such information maybe helpful as well. 3. As for subquery / joincnt, actually it is just helpful for optimizer developer to understand the query character is running most, it doesn't help much for user. The attached is a PoC, that is far from perfect since 1). It maintain a per-backend global variable query_character which is only used in pg_stat_statements extension. 2). The 5 fields is impossible to change no matter how many times it runs, so it can't be treat as Counter in nature. However I don't think the above 2 will cause big issues. I added the columns to V1_8 rather than adding a new version. this can be changed at final patch. Any suggestions? Best Regards Andy Fan
v1-0001-Add-query-characters-information-to-pg_stat_state.patch
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