Depends on a lot of thongs...Visibility map sounds like it's impacted here. Are your inserts towards the index (like a monotonically increasing serial id) or scattered around the index values ? How big is the table index and shared buffers ? An example would really help
On Sat, 21 Dec 2024, 11:51 James Pang, <jamespang...@gmail.com> wrote: > Hi, > we have a simple select .... from table where ... (that mache the > index) , table has 80million rows. when many application sessions run the > query and at the same time some other sessions doing insert into ... this > table. from pg_stat_statements, shared_blks_hit show 31652 / per call. we > see very high cpu almost 100% cpu during application workload test, and > high LWLock BufferMapping waiting for these querys. But manually run the > sql show only 2148 shared_blks_hit/ per call. this is a simple sql, from > pg_profile we did see it use same index scan as manually running. What > could be possible reason leading so big difference with shared_blks_hit ? > PGv14.8 > > Thanks, > > James >
