We recently upgraded os from rh 7.2 (2.4 kernel) to Suse 9.1 (2.6 kernel), and psql from 7.3.4 to 7.4.2

One of the quirks I've noticed is how the queries don't always have the same explain plans on the new psql... but that's a different email I think.

My main question is I'm trying to convince the powers that be to let me use persistent DB connections (from apache 2 / php), and my research has yielded conflicting documentation about the shared_buffers setting... real shocker there :)

For idle persistent connections, do each of them allocate the memory specified by this setting (shared_buffers * 8k), or is it one pool used by all the connection (which seems the logical conclusion based on the name SHARED_buffers)? Personally I'm more inclined to think the latter choice, but I've seen references that alluded to both cases, but never a definitive answer.

For what its worth, shared_buffers is currently set to 50000 (on a 4G system). Also, effective_cache_size is 125000. max_connections is 256, so I don't want to end up with a possible 100G (50k * 8k * 256) of memory tied up... not that it would be possible, but you never know.

I typically never see more than a dozen or so concurrent connections to the db (serving 3 web servers), so I'm thinking of actually using something like pgpool to keep about 10 per web server, rather than use traditional persistent connections of 1 per Apache child, which would probably average about 50 per web server.


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