On Mon, 2008-01-28 at 23:13 +0000, Heikki Linnakangas wrote:
> Tables that are seq scanned are typically very small, like a summary
> table with just a few rows, or huge tables in a data warehousing
> system. Between the extremes, I don't think the threshold actually has
> a very big impact.
And if you have a partitioned table with partitions inconveniently
sized? You'd need to *reduce* shared_buffers specifically to get synch
scans and BAS to kick in. Or increase partition size. Both of which
reduce the impact of the benefits we've added.
I don't think the argument that "a table is smaller than shared buffers
therefore it is already in shared buffers" holds true in all cases. I/O
does matter.
-- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com