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Simplify restriction handling of two-phase commit for temporary objects

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There were two flags used to track the access to temporary tables and
to the temporary namespace of a session which are used to restrict
PREPARE TRANSACTION, however the first control flag is a concept
included in the second.  This removes the flag for temporary table
tracking, keeping around only the one at namespace level.

Author: Michael Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20190118053126.GH1883@paquier.xyz
This commit is contained in:
Michael Paquier
2019-01-26 10:45:23 +09:00
parent df4c904440
commit c9b75c5838
7 changed files with 25 additions and 38 deletions
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19
src/backend/access/transam/xact.c
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@ -2266,6 +2266,11 @@ PrepareTransaction(void)
* clean up the source backend's local buffers and ON COMMIT state if the
* prepared xact includes a DROP of a temp table.
*
* Other objects types, like functions, operators or extensions, share the
* same restriction as they should not be created, locked or dropped as
* this can mess up with this session or even a follow-up session trying
* to use the same temporary namespace.
*
* We must check this after executing any ON COMMIT actions, because they
* might still access a temp relation.
*
@ -2273,22 +2278,10 @@ PrepareTransaction(void)
* cases, such as a temp table created and dropped all within the
* transaction. That seems to require much more bookkeeping though.
*/
if ((MyXactFlags & XACT_FLAGS_ACCESSEDTEMPREL))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has operated on temporary tables")));
/*
* Similarly, PREPARE TRANSACTION is not allowed if the temporary
* namespace has been involved in this transaction as we cannot allow it
* to create, lock, or even drop objects within the temporary namespace
* as this can mess up with this session or even a follow-up session
* trying to use the same temporary namespace.
*/
if ((MyXactFlags & XACT_FLAGS_ACCESSEDTEMPNAMESPACE))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has operated on temporary namespace")));
errmsg("cannot PREPARE a transaction that has operated on temporary objects")));
/*
* Likewise, don't allow PREPARE after pg_export_snapshot. This could be