Re: shared_buffer=2*max_connections?

> I see in postgresql.conf what seems to be the suggested way to go:
> 
> #shared_buffers = 2*max_connections # min 16
> 
> This seems to imply that every connection is to take 16kb of shmem on average. From my understanding this depends on the size of the query->involved relations, the sort_mem size etc.etc.

It is assuming two 8k buffers per backend.  They are shared.  This is
just an estimate and probably doesn't accurately show how many you will
need for your query load.

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