On Tue, May 29, 2012 at 11:42 PM, Tom Lane
<tgl@sss.pgh.pa.us> wrote:
While I'm looking at this, is the first test involving
effective_cache_size bulletproof either? In particular, is
avgIndexTuplesPerPage clamped to be strictly greater than 1?
It's based on collected statistics on already inserted tuple sizes. Since tuple sizes are measured after possible toasting, I don't see the way for avgIndexTuplesPerPage to be less than 1.
And for that matter, is either test sane from a units standpoint?
It seems to me that maxIndexTuplesPerPage would have units of
1/blocks, which is pretty dubious to be comparing to a block count
even disregarding the power function.
In this test we use avgIndexTuplesPerPage as estimate for number of child index pages of one page. I think we can assume it to have blocks unit.
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With best regards,
Alexander Korotkov.