I would like to understand how much can partitioning can contribute to memory usage in Postgres backend processes.
My application mainly runs SELECT statements in a partitioned table. The table is partitioned by size (100K rows per partition, 730 partitions in total). However, each Postgres backend process to run these SELECTs takes ~300 MB in memory, which seems a lot compared to what I've seen around.
work_mem is set to 16MB, so nothing too crazy. Also, I am using Pss to measure the memory used by each backend process so that shared_buffers don't mess the whole thing. Here's the output for a couple of them
Pss: 1260383 kB
Pss_Anon: 305501 kB
Pss_File: 199 kB
Pss_Shmem: 954682 kB
Pss: 1247796 kB
Pss_Anon: 293041 kB
Pss_File: 200 kB
Pss_Shmem: 954554 kB
Is this expected? Or the overhead of partitions should be smaller in terms of memory consumption? I'm using Partman to partition the table.
Also, shared_buffers for this instance is 25GB with a total of 60GB memory. I can provide output for explain (analyze, buffers) if needed, but the main index used for queries is fully in memory (it takes around 18GB of space).
