From: Tom Lane Date: Tue, 4 Mar 2008 19:54:23 +0000 (+0000) Subject: Fix PREPARE TRANSACTION to reject the case where the transaction has dropped a X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=a64f7f8dbf4ef139749d2a1676ede7a89c6b4d08;p=users%2Fbernd%2Fpostgres.git Fix PREPARE TRANSACTION to reject the case where the transaction has dropped a temporary table; we can't support that because there's no way to clean up the source backend's internal state if the eventual COMMIT PREPARED is done by another backend. This was checked correctly in 8.1 but I broke it in 8.2 :-(. Patch by Heikki Linnakangas, original trouble report by John Smith. --- diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index a7ad084809..41eb83d33e 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -699,6 +699,10 @@ relation_open(Oid relationId, LOCKMODE lockmode) if (!RelationIsValid(r)) elog(ERROR, "could not open relation with OID %u", relationId); + /* Make note that we've accessed a temporary relation */ + if (r->rd_istemp) + MyXactAccessedTempRel = true; + return r; } @@ -741,6 +745,10 @@ try_relation_open(Oid relationId, LOCKMODE lockmode) if (!RelationIsValid(r)) elog(ERROR, "could not open relation with OID %u", relationId); + /* Make note that we've accessed a temporary relation */ + if (r->rd_istemp) + MyXactAccessedTempRel = true; + return r; } @@ -785,6 +793,10 @@ relation_open_nowait(Oid relationId, LOCKMODE lockmode) if (!RelationIsValid(r)) elog(ERROR, "could not open relation with OID %u", relationId); + /* Make note that we've accessed a temporary relation */ + if (r->rd_istemp) + MyXactAccessedTempRel = true; + return r; } diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 384f5c9d6b..4256af975b 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -57,6 +57,13 @@ bool XactReadOnly; int CommitDelay = 0; /* precommit delay in microseconds */ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ +/* + * MyXactAccessedTempRel is set when a temporary relation is accessed. + * We don't allow PREPARE TRANSACTION in that case. (This is global + * so that it can be set from heapam.c.) + */ +bool MyXactAccessedTempRel = false; + /* * transaction states - transaction state from server perspective @@ -1389,6 +1396,7 @@ StartTransaction(void) FreeXactSnapshot(); XactIsoLevel = DefaultXactIsoLevel; XactReadOnly = DefaultXactReadOnly; + MyXactAccessedTempRel = false; /* * reinitialize within-transaction counters @@ -1715,6 +1723,26 @@ PrepareTransaction(void) /* NOTIFY and flatfiles will be handled below */ + /* + * Don't allow PREPARE TRANSACTION if we've accessed a temporary table + * in this transaction. Having the prepared xact hold locks on another + * backend's temp table seems a bad idea --- for instance it would prevent + * the backend from exiting. There are other problems too, such as how + * to clean up the source backend's local buffers and ON COMMIT state + * if the prepared xact includes a DROP of a temp table. + * + * We must check this after executing any ON COMMIT actions, because + * they might still access a temp relation. + * + * XXX In principle this could be relaxed to allow some useful special + * cases, such as a temp table created and dropped all within the + * transaction. That seems to require much more bookkeeping though. + */ + if (MyXactAccessedTempRel) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("cannot PREPARE a transaction that has operated on temporary tables"))); + /* Prevent cancel/die interrupt while cleaning up */ HOLD_INTERRUPTS(); diff --git a/src/backend/storage/lmgr/lmgr.c b/src/backend/storage/lmgr/lmgr.c index e8cc29523f..8b39bf4cae 100644 --- a/src/backend/storage/lmgr/lmgr.c +++ b/src/backend/storage/lmgr/lmgr.c @@ -19,12 +19,10 @@ #include "access/transam.h" #include "access/xact.h" #include "catalog/catalog.h" -#include "catalog/namespace.h" #include "miscadmin.h" #include "storage/lmgr.h" #include "storage/procarray.h" #include "utils/inval.h" -#include "utils/lsyscache.h" /* @@ -598,40 +596,3 @@ UnlockSharedObject(Oid classid, Oid objid, uint16 objsubid, LockRelease(&tag, lockmode, false); } - - -/* - * LockTagIsTemp - * Determine whether a locktag is for a lock on a temporary object - * - * We need this because 2PC cannot deal with temp objects - */ -bool -LockTagIsTemp(const LOCKTAG *tag) -{ - switch (tag->locktag_type) - { - case LOCKTAG_RELATION: - case LOCKTAG_RELATION_EXTEND: - case LOCKTAG_PAGE: - case LOCKTAG_TUPLE: - /* check for lock on a temp relation */ - /* field1 is dboid, field2 is reloid for all of these */ - if ((Oid) tag->locktag_field1 == InvalidOid) - return false; /* shared, so not temp */ - if (isTempNamespace(get_rel_namespace((Oid) tag->locktag_field2))) - return true; - break; - case LOCKTAG_TRANSACTION: - /* there are no temp transactions */ - break; - case LOCKTAG_OBJECT: - /* there are currently no non-table temp objects */ - break; - case LOCKTAG_USERLOCK: - case LOCKTAG_ADVISORY: - /* assume these aren't temp */ - break; - } - return false; /* default case */ -} diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c index 7cee97b1cf..1e3094e2b3 100644 --- a/src/backend/storage/lmgr/lock.c +++ b/src/backend/storage/lmgr/lock.c @@ -37,7 +37,6 @@ #include "access/twophase_rmgr.h" #include "miscadmin.h" #include "pgstat.h" -#include "storage/lmgr.h" #include "utils/memutils.h" #include "utils/ps_status.h" #include "utils/resowner.h" @@ -1849,12 +1848,6 @@ AtPrepare_Locks(void) elog(ERROR, "cannot PREPARE when session locks exist"); } - /* Can't handle it if the lock is on a temporary object */ - if (LockTagIsTemp(&locallock->tag.lock)) - ereport(ERROR, - (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), - errmsg("cannot PREPARE a transaction that has operated on temporary tables"))); - /* * Create a 2PC record. */ diff --git a/src/include/access/xact.h b/src/include/access/xact.h index 6543456aa7..3ee7216b70 100644 --- a/src/include/access/xact.h +++ b/src/include/access/xact.h @@ -41,6 +41,9 @@ extern int XactIsoLevel; extern bool DefaultXactReadOnly; extern bool XactReadOnly; +/* Kluge for 2PC support */ +extern bool MyXactAccessedTempRel; + /* * start- and end-of-transaction callbacks for dynamically loaded modules */ diff --git a/src/include/storage/lmgr.h b/src/include/storage/lmgr.h index a6358c3be0..b104dfc2d8 100644 --- a/src/include/storage/lmgr.h +++ b/src/include/storage/lmgr.h @@ -66,7 +66,4 @@ extern void LockSharedObject(Oid classid, Oid objid, uint16 objsubid, extern void UnlockSharedObject(Oid classid, Oid objid, uint16 objsubid, LOCKMODE lockmode); -/* Knowledge about which locktags describe temp objects */ -extern bool LockTagIsTemp(const LOCKTAG *tag); - #endif /* LMGR_H */