I don't quote know how this data but any constant factor seems like it
would be arbitrary. It sounds like a more principled algorithm would
be to use stats_target^2. But that has the same problem. Even
stats_target^1.5 would be too big for stats_target 10,000.
I think just using 10 is probably the right thing.
--
Greg
On 13 Dec 2008, at 13:02, Tom Lane <t...@sss.pgh.pa.us> wrote:
I started making the changes to increase the default and maximum stats
targets 10X, as I believe was agreed to in this thread:
http://archives.postgresql.org/pgsql-hackers/2008-12/msg00386.php
I came across this bit in ts_typanalyze.c:
/* We want statistic_target * 100 lexemes in the MCELEM array */
num_mcelem = stats->attr->attstattarget * 100;
I wonder whether the multiplier here should be changed? This code is
new for 8.4, so we have zero field experience about what desirable
lexeme counts are; but the prospect of up to a million lexemes in
a pg_statistic entry doesn't seem quite right. I'm tempted to cut the
multiplier to 10 so that the effective range of MCELEM sizes remains
the same as what Jan had in mind when he wrote the code.
regards, tom lane
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