Horton

Re: BUG #16045: vacuum_db crash and illegal memory alloc after pg_upgrade from PG11 to PG12

Tom Lane <tgl@sss.pgh.pa.us>

View thread
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>, buschmann@nidsa.net, pgsql-bugs@lists.postgresql.org
Date: 2019-10-14T14:16:40Z
Lists: pgsql-bugs, pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Move into separate file all the SQL queries used in pg_upgrade tests

  2. Add table to regression tests for binary-compatibility checks in pg_upgrade

  3. Fix tests of pg_upgrade across different major versions

  4. Multirange datatypes

  5. Work around cross-version-upgrade issues created by commit 9e38c2bb5.

  6. Declare assorted array functions using anycompatible not anyelement.

  7. Remove factorial operators, leaving only the factorial() function.

  8. Create by default sql/ and expected/ for output directory in pg_regress

  9. Add missing include to pg_upgrade/version.c

  10. Improve the check for pg_catalog.line data type in pg_upgrade

  11. Improve the check for pg_catalog.unknown data type in pg_upgrade

  12. Check for tables with sql_identifier during pg_upgrade

  13. pg_upgrade: clarify the database names in error files

  14. In the pg_upgrade test suite, don't write to src/test/regress.

  15. Allow group access on PGDATA

  16. Refactor dir/file permissions

  17. Remove unused functions in regress.c.

  18. Make WAL segment size configurable at initdb time.

  19. Fix bit-rot in pg_upgrade's test.sh, and improve documentation.

Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On Sun, Oct 13, 2019 at 02:26:48PM -0400, Tom Lane wrote:
>> Might be a good idea to exclude attisdropped columns in the part of the
>> recursive query that's looking for sql_identifier columns of composite
>> types.  I'm not sure if composites can have dropped columns today,

[ I checked this, they can ]

>> but even if they can't it seems like a wise bit of future-proofing.
>> (We'll no doubt have occasion to use this logic again...)

> Hmm? How could that be safe? Let's say we have a composite type with a
> sql_identifier column, it's used in a table with data, and we drop the
> column. We need the pg_type information to parse the existing, so how
> could we skip attisdropped columns?

It works exactly like it does for table rowtypes.

regression=# create type cfoo as (f1 int, f2 int, f3 int);
CREATE TYPE
regression=# alter type cfoo drop attribute f2;
ALTER TYPE
regression=# select attname,atttypid,attisdropped,attlen,attalign from pg_attribute where attrelid = 'cfoo'::regclass;
           attname            | atttypid | attisdropped | attlen | attalign 
------------------------------+----------+--------------+--------+----------
 f1                           |       23 | f            |      4 | i
 ........pg.dropped.2........ |        0 | t            |      4 | i
 f3                           |       23 | f            |      4 | i
(3 rows)

All we need to skip over the dead data is attlen/attalign, which are
preserved in pg_attribute even if the pg_type row is gone.

As this example shows, you don't really *have* to check attisdropped
because atttypid will be set to zero.  But the latter is just a
defense measure in case somebody forgets to check attisdropped;
you're not supposed to forget that.

			regards, tom lane