Re: FSM search modes - Mailing list pgsql-hackers

From Tom Lane
Subject Re: FSM search modes
Date
Msg-id 1412.1254423318@sss.pgh.pa.us
Whole thread Raw
In response to Re: FSM search modes  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
List pgsql-hackers
"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> So for example we might try resetting the search to the start of the
>> relation with probability 0.01.
> If I understand the heuristic you propose, and my math skill haven't
> eroded too badly from lack of use, every 229 spots considered would
> cause a 90% chance of reset.

Sorry, I wasn't clear.  What I was thinking of was that we'd consider
resetting the search position once, upon entry to fsm_search, and then
search normally thereafter.  Some experimentation would be needed to
choose the right probability of course.  A number like 0.01 might seem
too small to affect the behavior at all, but that's what we thought
about the btree case too.  A very light thumb upon the scales may be
sufficient.
        regards, tom lane


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