Horton

Re: longfin and tamandua aren't too happy but I'm not sure why

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Justin Pryzby <pryzby@telsasoft.com>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2022-09-28T13:16:19Z
Lists: pgsql-hackers 
On Tue, Sep 27, 2022 at 5:50 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Maybe it wouldn't have any great impact.  I don't know, but I don't
> think it's incumbent on me to measure that.  You or the patch author
> should have had a handle on that question *before* committing.

I agree. I should have gone through and checked that every place where
RelFileLocator got embedded in some larger struct, there was no
problem with making it bigger and increasing the alignment
requirement. I'll go back and do that as soon as the immediate
problems are fixed. This case would have stood out as something
needing attention.

Some of the cases are pretty subtle, though. tamandua is still unhappy
even after pushing that fix, because xl_xact_relfilelocators embeds a
RelFileLocator which now requires 8-byte alignment, and
ParseCommitRecord has an undocumented assumption that none of the
things embedded in a commit record require more than 4-byte alignment.
Really, if it's critical for a struct to never require more than
4-byte alignment, there ought to be a comment about that *on the
struct itself*. Having a comment on a function that does something
with that struct is probably not really good enough, and we don't even
have that.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. meson: Split 'main' suite into 'regress' and 'isolation'

  2. ci: Add 32bit build and test

  3. Fix InitializeRelfilenumberMap for 05d4cbf9b6ba708858984b01ca0fc56d59d4ec7c

  4. Fix alignment problems with SharedInvalSmgrMsg.

  5. In BufTagGetForkNum, cast to the correct type.

  6. Increase width of RelFileNumbers from 32 bits to 56 bits.

  7. Harden pg_filenode_relation test against concurrent DROP TABLE.