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Set cutoff xmin more aggressively when vacuuming a temporary table.

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Since other sessions aren't allowed to look into a temporary table
of our own session, we do not need to worry about the global xmin
horizon when setting the vacuum XID cutoff.  Indeed, if we're not
inside a transaction block, we may set oldestXmin to be the next
XID, because there cannot be any in-doubt tuples in a temp table,
nor any tuples that are dead but still visible to some snapshot of
our transaction.  (VACUUM, of course, is never inside a transaction
block; but we need to test that because CLUSTER shares the same code.)

This approach allows us to always clean out a temp table completely
during VACUUM, independently of concurrent activity.  Aside from
being useful in its own right, that simplifies building reproducible
test cases.

Discussion: https://postgr.es/m/3490536.1598629609@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2020-09-01 18:37:12 -04:00
parent db864c3c36
commit a7212be8b9
5 changed files with 70 additions and 36 deletions
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28
src/backend/commands/cluster.c
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@ -67,10 +67,13 @@ typedef struct
} RelToCluster;
static void rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose);
static void rebuild_relation(Relation OldHeap, Oid indexOid,
bool isTopLevel, bool verbose);
static void copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
bool verbose, bool *pSwapToastByContent,
TransactionId *pFreezeXid, MultiXactId *pCutoffMulti);
bool isTopLevel, bool verbose,
bool *pSwapToastByContent,
TransactionId *pFreezeXid,
MultiXactId *pCutoffMulti);
static List *get_tables_to_cluster(MemoryContext cluster_context);
@ -170,7 +173,7 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
table_close(rel, NoLock);
/* Do the job. */
cluster_rel(tableOid, indexOid, stmt->options);
cluster_rel(tableOid, indexOid, stmt->options, isTopLevel);
}
else
{
@ -219,7 +222,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
PushActiveSnapshot(GetTransactionSnapshot());
/* Do the job. */
cluster_rel(rvtc->tableOid, rvtc->indexOid,
stmt->options | CLUOPT_RECHECK);
stmt->options | CLUOPT_RECHECK,
isTopLevel);
PopActiveSnapshot();
CommitTransactionCommand();
}
@ -250,7 +254,7 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
* and error messages should refer to the operation as VACUUM not CLUSTER.
*/
void
cluster_rel(Oid tableOid, Oid indexOid, int options)
cluster_rel(Oid tableOid, Oid indexOid, int options, bool isTopLevel)
{
Relation OldHeap;
bool verbose = ((options & CLUOPT_VERBOSE) != 0);
@ -400,7 +404,7 @@ cluster_rel(Oid tableOid, Oid indexOid, int options)
TransferPredicateLocksToHeapRelation(OldHeap);
/* rebuild_relation does all the dirty work */
rebuild_relation(OldHeap, indexOid, verbose);
rebuild_relation(OldHeap, indexOid, isTopLevel, verbose);
/* NB: rebuild_relation does table_close() on OldHeap */
@ -545,11 +549,12 @@ mark_index_clustered(Relation rel, Oid indexOid, bool is_internal)
*
* OldHeap: table to rebuild --- must be opened and exclusive-locked!
* indexOid: index to cluster by, or InvalidOid to rewrite in physical order.
* isTopLevel: should be passed down from ProcessUtility.
*
* NB: this routine closes OldHeap at the right time; caller should not.
*/
static void
rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
rebuild_relation(Relation OldHeap, Oid indexOid, bool isTopLevel, bool verbose)
{
Oid tableOid = RelationGetRelid(OldHeap);
Oid tableSpace = OldHeap->rd_rel->reltablespace;
@ -577,7 +582,7 @@ rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
AccessExclusiveLock);
/* Copy the heap data into the new table in the desired order */
copy_table_data(OIDNewHeap, tableOid, indexOid, verbose,
copy_table_data(OIDNewHeap, tableOid, indexOid, isTopLevel, verbose,
&swap_toast_by_content, &frozenXid, &cutoffMulti);
/*
@ -728,7 +733,8 @@ make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, char relpersistence,
* *pCutoffMulti receives the MultiXactId used as a cutoff point.
*/
static void
copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose,
copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
bool isTopLevel, bool verbose,
bool *pSwapToastByContent, TransactionId *pFreezeXid,
MultiXactId *pCutoffMulti)
{
@ -826,7 +832,7 @@ copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose,
* Since we're going to rewrite the whole table anyway, there's no reason
* not to be aggressive about this.
*/
vacuum_set_xid_limits(OldHeap, 0, 0, 0, 0,
vacuum_set_xid_limits(OldHeap, 0, 0, 0, 0, isTopLevel,
&OldestXmin, &FreezeXid, NULL, &MultiXactCutoff,
NULL);