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Restructure subtransaction handling to reduce resource consumption,

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as per recent discussions.  Invent SubTransactionIds that are managed like
CommandIds (ie, counter is reset at start of each top transaction), and
use these instead of TransactionIds to keep track of subtransaction status
in those modules that need it.  This means that a subtransaction does not
need an XID unless it actually inserts/modifies rows in the database.
Accordingly, don't assign it an XID nor take a lock on the XID until it
tries to do that.  This saves a lot of overhead for subtransactions that
are only used for error recovery (eg plpgsql exceptions).  Also, arrange
to release a subtransaction's XID lock as soon as the subtransaction
exits, in both the commit and abort cases.  This avoids holding many
unique locks after a long series of subtransactions.  The price is some
additional overhead in XactLockTableWait, but that seems acceptable.
Finally, restructure the state machine in xact.c to have a more orthogonal
set of states for subtransactions.
This commit is contained in:
Tom Lane
2004-09-16 16:58:44 +00:00
parent 42c0d1f3cd
commit 8f9f198603
34 changed files with 1220 additions and 945 deletions
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22
src/backend/access/heap/heapam.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.174 2004/09/11 18:28:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.175 2004/09/16 16:58:25 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -1108,6 +1108,7 @@ heap_get_latest_tid(Relation relation,
Oid
heap_insert(Relation relation, HeapTuple tup, CommandId cid)
{
TransactionId xid = GetCurrentTransactionId();
Buffer buffer;
if (relation->rd_rel->relhasoids)
@ -1139,7 +1140,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid)
tup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
tup->t_data->t_infomask |= HEAP_XMAX_INVALID;
HeapTupleHeaderSetXmin(tup->t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmin(tup->t_data, xid);
HeapTupleHeaderSetCmin(tup->t_data, cid);
HeapTupleHeaderSetCmax(tup->t_data, 0); /* zero out Datum fields */
tup->t_tableOid = relation->rd_id;
@ -1277,6 +1278,7 @@ heap_delete(Relation relation, ItemPointer tid,
ItemPointer ctid, CommandId cid,
Snapshot crosscheck, bool wait)
{
TransactionId xid = GetCurrentTransactionId();
ItemId lp;
HeapTupleData tp;
PageHeader dp;
@ -1365,7 +1367,7 @@ l1:
HEAP_XMAX_INVALID |
HEAP_MARKED_FOR_UPDATE |
HEAP_MOVED);
HeapTupleHeaderSetXmax(tp.t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmax(tp.t_data, xid);
HeapTupleHeaderSetCmax(tp.t_data, cid);
/* Make sure there is no forward chain link in t_ctid */
tp.t_data->t_ctid = tp.t_self;
@ -1495,6 +1497,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
ItemPointer ctid, CommandId cid,
Snapshot crosscheck, bool wait)
{
TransactionId xid = GetCurrentTransactionId();
ItemId lp;
HeapTupleData oldtup;
PageHeader dp;
@ -1603,7 +1606,7 @@ l2:
newtup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
newtup->t_data->t_infomask |= (HEAP_XMAX_INVALID | HEAP_UPDATED);
HeapTupleHeaderSetXmin(newtup->t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmin(newtup->t_data, xid);
HeapTupleHeaderSetCmin(newtup->t_data, cid);
HeapTupleHeaderSetCmax(newtup->t_data, 0); /* zero out Datum fields */
@ -1644,7 +1647,7 @@ l2:
HEAP_MARKED_FOR_UPDATE |
HEAP_MOVED);
oldtup.t_data->t_infomask |= HEAP_XMAX_UNLOGGED;
HeapTupleHeaderSetXmax(oldtup.t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
HeapTupleHeaderSetCmax(oldtup.t_data, cid);
already_marked = true;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
@ -1735,7 +1738,7 @@ l2:
HEAP_XMAX_INVALID |
HEAP_MARKED_FOR_UPDATE |
HEAP_MOVED);
HeapTupleHeaderSetXmax(oldtup.t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
HeapTupleHeaderSetCmax(oldtup.t_data, cid);
}
@ -1836,6 +1839,7 @@ int
heap_mark4update(Relation relation, HeapTuple tuple, Buffer *buffer,
CommandId cid)
{
TransactionId xid = GetCurrentTransactionId();
ItemPointer tid = &(tuple->t_self);
ItemId lp;
PageHeader dp;
@ -1912,7 +1916,7 @@ l3:
HEAP_XMAX_INVALID |
HEAP_MOVED);
tuple->t_data->t_infomask |= HEAP_MARKED_FOR_UPDATE;
HeapTupleHeaderSetXmax(tuple->t_data, GetCurrentTransactionId());
HeapTupleHeaderSetXmax(tuple->t_data, xid);
HeapTupleHeaderSetCmax(tuple->t_data, cid);
/* Make sure there is no forward chain link in t_ctid */
tuple->t_data->t_ctid = *tid;
@ -2584,6 +2588,7 @@ newsame:;
static void
_heap_unlock_tuple(void *data)
{
TransactionId xid = GetCurrentTransactionId();
xl_heaptid *xltid = (xl_heaptid *) data;
Relation reln = XLogOpenRelation(false, RM_HEAP_ID, xltid->node);
Buffer buffer;
@ -2614,13 +2619,12 @@ _heap_unlock_tuple(void *data)
htup = (HeapTupleHeader) PageGetItem(page, lp);
if (!TransactionIdEquals(HeapTupleHeaderGetXmax(htup), GetCurrentTransactionId()))
if (!TransactionIdEquals(HeapTupleHeaderGetXmax(htup), xid))
elog(PANIC, "_heap_unlock_tuple: invalid xmax in rollback");
htup->t_infomask &= ~HEAP_XMAX_UNLOGGED;
htup->t_infomask |= HEAP_XMAX_INVALID;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
WriteBuffer(buffer);
return;
}
void