| 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 19:34:13 |
| Message-ID: | 1468522.1740425653@sss.pgh.pa.us |
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Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> We certainly want attnames for tables to keep it working reasonably
> well for cases where the user might be doing something more interesting
> than a binary upgrade, as you point out. But attribute numbers for
> indexes seem much more reliable: an index with a different attribute
> order is a fundamentally different index.
Right. We went through pretty much this reasoning, as I recall,
when we invented ALTER INDEX ... SET STATISTICS. The original
version used a column name like ALTER TABLE did, and we ran into
exactly the present problem that the names aren't too stable across
dump/restore, and we decided that index column numbers would do
instead. You can't add or drop a column of an index, nor redefine it
meaningfully, except by dropping the whole index which will make any
associated stats go away.
The draft patch I posted allows callers to use attname or attnum
at their option, because I didn't see a reason to restrict that.
But I envisioned that pg_dump would always use attname for table
columns and attnum for index columns.
regards, tom lane
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