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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2018-10-01 11:39:14 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2018-10-01 11:39:14 -0400 |
| commit | 0031e9d6ab8063f0c7fcf420270bd1e86abd7d18 (patch) | |
| tree | a9e7e6b565fca4f2b0b7395ef89607b5f8528a59 /src/backend/utils/adt/xml.c | |
| parent | 8b36dc588d100d1bc8007f21fd2c2a1504dbc4f7 (diff) | |
| download | postgresql-0031e9d6ab8063f0c7fcf420270bd1e86abd7d18.tar.gz postgresql-0031e9d6ab8063f0c7fcf420270bd1e86abd7d18.zip | |
Fix ALTER COLUMN TYPE to not open a relation without any lock.
If the column being modified is referenced by a foreign key constraint
of another table, ALTER TABLE would open the other table (to re-parse
the constraint's definition) without having first obtained a lock on it.
This was evidently intentional, but that doesn't mean it's really safe.
It's especially not safe in 9.3, which pre-dates use of MVCC scans for
catalog reads, but even in current releases it doesn't seem like a good
idea.
We know we'll need AccessExclusiveLock shortly to drop the obsoleted
constraint, so just get that a little sooner to close the hole.
Per testing with a patch that complains if we open a relation without
holding any lock on it. I don't plan to back-patch that patch, but we
should close the holes it identifies in all supported branches.
Discussion: https://postgr.es/m/2038.1538335244@sss.pgh.pa.us
Diffstat (limited to 'src/backend/utils/adt/xml.c')
0 files changed, 0 insertions, 0 deletions