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It does, but AFAIk only for prepapred queries and cache is local to the backend serving query. See `plan_cache_mode` param.

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Which has very limited usefulness since it only last for the session, so it helps if you are say doing the same query over and over on the same connection like bulk inserts but does not help for say the same select use over different requests where the connection is closed or given back to pool on each request which is far more common and would probably line up with the or/in issue here.

I don't even think PG caches plans for functions/sprocs. Back in the day with MSSQL before it had full plan caching based on statement text you could at least make sprocs for common queries and get plan reuse which had a large impact on perf in many apps.

Typically you try and avoid closing a connection on each request, you hand it back to a connection pool. The underlying session stays open and associated with the connection (if you have your pooler set up right), so subsequent requests still use the cache.

I agree with the original commenter about ANY as well: using IN for dynamic lists of parameters makes viewing useful information in e.g pg_stat_statements impossible, though it's possible there's been some recent work around normalizing these.

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