database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Introduce GUC_NO_RESET flag.

Browse Source 
Previously, the transaction-property GUCs such as transaction_isolation
could be reset after starting a transaction, because we marked them
as GUC_NO_RESET_ALL but still allowed a targeted RESET.  That leads to
assertion failures or worse, because those properties aren't supposed
to change after we've acquired a transaction snapshot.

There are some NO_RESET_ALL variables for which RESET is okay, so
we can't just redefine the semantics of that flag.  Instead introduce
a separate GUC_NO_RESET flag.  Mark "seed", as well as the transaction
property GUCs, as GUC_NO_RESET.

We have to disallow GUC_ACTION_SAVE as well as straight RESET, because
otherwise a function having a "SET transaction_isolation" clause can
still break things: the end-of-function restore action is equivalent
to a RESET.

No back-patch, as it's conceivable that someone is doing something
this patch will forbid (like resetting one of these GUCs at transaction
start, or "CREATE FUNCTION ... SET transaction_read_only = 1") and not
running into problems with it today.  Given how long we've had this
issue and not noticed, the side effects in non-assert builds can't be
too serious.

Per bug #17385 from Andrew Bille.

Masahiko Sawada

Discussion: https://postgr.es/m/17385-9ee529fb091f0ce5@postgresql.org
This commit is contained in:
Tom Lane
2022-09-27 11:47:12 -04:00
parent 4148c8b3da
commit 3853664265
11 changed files with 103 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
src/backend/utils/misc/guc.c
View File

@ -3243,6 +3243,26 @@ set_config_option_ext(const char *name, const char *value,
}
}
/* Disallow resetting and saving GUC_NO_RESET values */
if (record->flags & GUC_NO_RESET)
{
if (value == NULL)
{
ereport(elevel,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("parameter \"%s\" cannot be reset", name)));
return 0;
}
if (action == GUC_ACTION_SAVE)
{
ereport(elevel,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("parameter \"%s\" cannot be set locally in functions",
name)));
return 0;
}
}
/*
* Should we set reset/stacked values? (If so, the behavior is not
* transactional.) This is done either when we get a default value from