database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-07 19:06:32 +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

7
src/backend/utils/misc/guc_funcs.c
View File

@@ -141,9 +141,6 @@ ExecSetVariableStmt(VariableSetStmt *stmt, bool isTopLevel)
WarnNoTransactionBlock(isTopLevel, "SET LOCAL");
/* fall through */
case VAR_RESET:
if (strcmp(stmt->name, "transaction_isolation") == 0)
WarnNoTransactionBlock(isTopLevel, "RESET TRANSACTION");
(void) set_config_option(stmt->name,
NULL,
(superuser() ? PGC_SUSET : PGC_USERSET),
@@ -539,7 +536,7 @@ ShowAllGUCConfig(DestReceiver *dest)
Datum
pg_settings_get_flags(PG_FUNCTION_ARGS)
{
#define MAX_GUC_FLAGS 5
#define MAX_GUC_FLAGS 6
char *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
struct config_generic *record;
int cnt = 0;
@@ -554,6 +551,8 @@ pg_settings_get_flags(PG_FUNCTION_ARGS)
if (record->flags & GUC_EXPLAIN)
flags[cnt++] = CStringGetTextDatum("EXPLAIN");
if (record->flags & GUC_NO_RESET)
flags[cnt++] = CStringGetTextDatum("NO_RESET");
if (record->flags & GUC_NO_RESET_ALL)
flags[cnt++] = CStringGetTextDatum("NO_RESET_ALL");
if (record->flags & GUC_NO_SHOW_ALL)