| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, jian he <jian(dot)universality(at)gmail(dot)com>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Stephen Frost <sfrost(at)snowman(dot)net>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, alvherre(at)alvh(dot)no-ip(dot)org |
| Subject: | Re: Statistics Import and Export |
| Date: | 2025-02-24 20:03:58 |
| Message-ID: | 1471693.1740427438@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> But you have a point in that float4in() does slightly more work than
> strtof() to handle platform differences about NaN/Inf. I'm not sure how
> much to weigh that concern, but I agree that there is non-zero
> cognitive overhead here.
If we're speaking strictly about the reltuples value, I'm not hugely
concerned about that. reltuples should never be NaN or Inf. There
is a nonzero chance that it will round off to a fractionally
different value if we pass it through strtof/sprintf on the pg_dump
side, but nobody is really going to care about that. (Maybe our
own pg_dump test script would, thanks to its not-too-bright dump
comparison logic. But that script is never going to see reltuples
values that are big enough to be inexact in a float4.)
I do buy the better-preserve-it-exactly argument for other sorts
of statistics, where we don't have such a good sense of what might
matter.
regards, tom lane
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