Cédric Villemain wrote:
AFAIK effective_cache_size is estimation of OS Page Cache + Estimated Cache in shared_buffers.
Yes, the total value you set is used as is, and should include both pieces of memory. The planner doesn't add the shared_buffers value to the total first for you, as some people might guess it would. The only thing effective_cache_size is used for is estimating how expensive an index is likely to be to use, to make decisions like when to do an index-based scan instead of just scanning the table itself.
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