Re: hist boundary duplicates bug in head and 8.3 - Mailing list pgsql-hackers

From Tom Lane
Subject Re: hist boundary duplicates bug in head and 8.3
Date
Msg-id 13427.1231285209@sss.pgh.pa.us
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In response to Re: hist boundary duplicates bug in head and 8.3  ("Nathan Boley" <npboley@gmail.com>)
Responses Re: hist boundary duplicates bug in head and 8.3  (Simon Riggs <simon@2ndQuadrant.com>)
List pgsql-hackers
"Nathan Boley" <npboley@gmail.com> writes:
>> I don't think this is a bug.

> hmmm... Well, I assumed it was a bug from a comment in analyze.

> From ( near ) line 2130 in analyze.c

>  * least 2 instances in the sample.  Also, we won't suppress values
>  * that have a frequency of at least 1/K where K is the intended
>  * number of histogram bins; such values might otherwise cause us to
>  * emit duplicate histogram bin boundaries.

That's talking about a case where we have a choice whether to include a
value in the MCV list or not.  Once the MCV list is maxed out, we can't
do anything to avoid duplicates.
        regards, tom lane


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