*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.257 2008/01/15 18:56:59 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.260 2008/03/17 19:44:41 petere Exp $
*
*-------------------------------------------------------------------------
*/
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/xml.h"
+#include "pg_trace.h"
/*
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
int gucNestLevel; /* GUC context nesting depth */
MemoryContext curTransactionContext; /* my xact-lifetime context */
ResourceOwner curTransactionOwner; /* my query resources */
- List *childXids; /* subcommitted child XIDs */
+ TransactionId *childXids; /* subcommitted child XIDs, in XID order */
+ int nChildXids; /* # of subcommitted child XIDs */
+ int maxChildXids; /* allocated size of childXids[] */
Oid prevUser; /* previous CurrentUserId setting */
bool prevSecDefCxt; /* previous SecurityDefinerContext setting */
bool prevXactReadOnly; /* entry-time xact r/o state */
0, /* GUC context nesting depth */
NULL, /* cur transaction context */
NULL, /* cur transaction resource owner */
- NIL, /* subcommitted child Xids */
+ NULL, /* subcommitted child Xids */
+ 0, /* # of subcommitted child Xids */
+ 0, /* allocated size of childXids[] */
InvalidOid, /* previous CurrentUserId setting */
false, /* previous SecurityDefinerContext setting */
false, /* entry-time xact r/o state */
*/
for (s = CurrentTransactionState; s != NULL; s = s->parent)
{
- ListCell *cell;
+ int low, high;
if (s->state == TRANS_ABORT)
continue;
continue; /* it can't have any child XIDs either */
if (TransactionIdEquals(xid, s->transactionId))
return true;
- foreach(cell, s->childXids)
+ /* As the childXids array is ordered, we can use binary search */
+ low = 0;
+ high = s->nChildXids - 1;
+ while (low <= high)
{
- if (TransactionIdEquals(xid, lfirst_xid(cell)))
+ int middle;
+ TransactionId probe;
+
+ middle = low + (high - low) / 2;
+ probe = s->childXids[middle];
+ if (TransactionIdEquals(probe, xid))
return true;
+ else if (TransactionIdPrecedes(probe, xid))
+ low = middle + 1;
+ else
+ high = middle - 1;
}
}
/* Clean up local data */
if (rels)
pfree(rels);
- if (children)
- pfree(children);
return latestXid;
}
AtSubCommit_childXids(void)
{
TransactionState s = CurrentTransactionState;
- MemoryContext old_cxt;
+ int new_nChildXids;
Assert(s->parent != NULL);
/*
- * We keep the child-XID lists in TopTransactionContext; this avoids
- * setting up child-transaction contexts for what might be just a few
- * bytes of grandchild XIDs.
+ * The parent childXids array will need to hold my XID and all my
+ * childXids, in addition to the XIDs already there.
*/
- old_cxt = MemoryContextSwitchTo(TopTransactionContext);
-
- s->parent->childXids = lappend_xid(s->parent->childXids,
- s->transactionId);
+ new_nChildXids = s->parent->nChildXids + s->nChildXids + 1;
- if (s->childXids != NIL)
+ /* Allocate or enlarge the parent array if necessary */
+ if (s->parent->maxChildXids < new_nChildXids)
{
- s->parent->childXids = list_concat(s->parent->childXids,
- s->childXids);
+ int new_maxChildXids;
+ TransactionId *new_childXids;
/*
- * list_concat doesn't free the list header for the second list; do so
- * here to avoid memory leakage (kluge)
+ * Make it 2x what's needed right now, to avoid having to enlarge it
+ * repeatedly. But we can't go above MaxAllocSize. (The latter
+ * limit is what ensures that we don't need to worry about integer
+ * overflow here or in the calculation of new_nChildXids.)
*/
- pfree(s->childXids);
- s->childXids = NIL;
+ new_maxChildXids = Min(new_nChildXids * 2,
+ (int) (MaxAllocSize / sizeof(TransactionId)));
+
+ if (new_maxChildXids < new_nChildXids)
+ ereport(ERROR,
+ (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+ errmsg("maximum number of committed subtransactions (%d) exceeded",
+ (int) (MaxAllocSize / sizeof(TransactionId)))));
+
+ /*
+ * We keep the child-XID arrays in TopTransactionContext; this avoids
+ * setting up child-transaction contexts for what might be just a few
+ * bytes of grandchild XIDs.
+ */
+ if (s->parent->childXids == NULL)
+ new_childXids =
+ MemoryContextAlloc(TopTransactionContext,
+ new_maxChildXids * sizeof(TransactionId));
+ else
+ new_childXids = repalloc(s->parent->childXids,
+ new_maxChildXids * sizeof(TransactionId));
+
+ s->parent->childXids = new_childXids;
+ s->parent->maxChildXids = new_maxChildXids;
}
- MemoryContextSwitchTo(old_cxt);
+ /*
+ * Copy all my XIDs to parent's array.
+ *
+ * Note: We rely on the fact that the XID of a child always follows that
+ * of its parent. By copying the XID of this subtransaction before the
+ * XIDs of its children, we ensure that the array stays ordered. Likewise,
+ * all XIDs already in the array belong to subtransactions started and
+ * subcommitted before us, so their XIDs must precede ours.
+ */
+ s->parent->childXids[s->parent->nChildXids] = s->transactionId;
+
+ if (s->nChildXids > 0)
+ memcpy(&s->parent->childXids[s->parent->nChildXids + 1],
+ s->childXids,
+ s->nChildXids * sizeof(TransactionId));
+
+ s->parent->nChildXids = new_nChildXids;
+
+ /* Release child's array to avoid leakage */
+ if (s->childXids != NULL)
+ pfree(s->childXids);
+ /* We must reset these to avoid double-free if fail later in commit */
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
}
/*
/* And clean up local data */
if (rels)
pfree(rels);
- if (children)
- pfree(children);
return latestXid;
}
TransactionState s = CurrentTransactionState;
/*
- * We keep the child-XID lists in TopTransactionContext (see
- * AtSubCommit_childXids). This means we'd better free the list
+ * We keep the child-XID arrays in TopTransactionContext (see
+ * AtSubCommit_childXids). This means we'd better free the array
* explicitly at abort to avoid leakage.
*/
- list_free(s->childXids);
- s->childXids = NIL;
+ if (s->childXids != NULL)
+ pfree(s->childXids);
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
}
/* ----------------------------------------------------------------
XactIsoLevel = DefaultXactIsoLevel;
XactReadOnly = DefaultXactReadOnly;
forceSyncCommit = false;
+ MyXactAccessedTempRel = false;
/*
* reinitialize within-transaction counters
Assert(MyProc->backendId == vxid.backendId);
MyProc->lxid = vxid.localTransactionId;
- PG_TRACE1(transaction__start, vxid.localTransactionId);
+ TRACE_POSTGRESQL_TRANSACTION_START(vxid.localTransactionId);
/*
* set transaction_timestamp() (a/k/a now()). We want this to be the same
*/
s->nestingLevel = 1;
s->gucNestLevel = 1;
- s->childXids = NIL;
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
GetUserIdAndContext(&s->prevUser, &s->prevSecDefCxt);
/* SecurityDefinerContext should never be set outside a transaction */
Assert(!s->prevSecDefCxt);
*/
latestXid = RecordTransactionCommit();
- PG_TRACE1(transaction__commit, MyProc->lxid);
+ TRACE_POSTGRESQL_TRANSACTION_COMMIT(MyProc->lxid);
/*
* Let others know about no transaction in progress by me. Note that this
s->subTransactionId = InvalidSubTransactionId;
s->nestingLevel = 0;
s->gucNestLevel = 0;
- s->childXids = NIL;
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
/*
* done with commit processing, set current transaction state back to
/* 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();
s->subTransactionId = InvalidSubTransactionId;
s->nestingLevel = 0;
s->gucNestLevel = 0;
- s->childXids = NIL;
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
/*
* done with 1st phase commit processing, set current transaction state
*/
latestXid = RecordTransactionAbort(false);
- PG_TRACE1(transaction__abort, MyProc->lxid);
+ TRACE_POSTGRESQL_TRANSACTION_ABORT(MyProc->lxid);
/*
* Let others know about no transaction in progress by me. Note that this
s->subTransactionId = InvalidSubTransactionId;
s->nestingLevel = 0;
s->gucNestLevel = 0;
- s->childXids = NIL;
+ s->childXids = NULL;
+ s->nChildXids = 0;
+ s->maxChildXids = 0;
/*
* done with abort processing, set current transaction state back to
static void
ShowTransactionStateRec(TransactionState s)
{
+ StringInfoData buf;
+
+ initStringInfo(&buf);
+
+ if (s->nChildXids > 0)
+ {
+ int i;
+
+ appendStringInfo(&buf, "%u", s->childXids[0]);
+ for (i = 1; i < s->nChildXids; i++)
+ appendStringInfo(&buf, " %u", s->childXids[i]);
+ }
+
if (s->parent)
ShowTransactionStateRec(s->parent);
(unsigned int) s->subTransactionId,
(unsigned int) currentCommandId,
currentCommandIdUsed ? " (used)" : "",
- s->nestingLevel,
- nodeToString(s->childXids))));
+ s->nestingLevel, buf.data)));
+
+ pfree(buf.data);
}
/*
* xactGetCommittedChildren
*
* Gets the list of committed children of the current transaction. The return
- * value is the number of child transactions. *children is set to point to a
- * palloc'd array of TransactionIds. If there are no subxacts, *children is
- * set to NULL.
+ * value is the number of child transactions. *ptr is set to point to an
+ * array of TransactionIds. The array is allocated in TopTransactionContext;
+ * the caller should *not* pfree() it (this is a change from pre-8.4 code!).
+ * If there are no subxacts, *ptr is set to NULL.
*/
int
xactGetCommittedChildren(TransactionId **ptr)
{
TransactionState s = CurrentTransactionState;
- int nchildren;
- TransactionId *children;
- ListCell *p;
- nchildren = list_length(s->childXids);
- if (nchildren == 0)
- {
+ if (s->nChildXids == 0)
*ptr = NULL;
- return 0;
- }
-
- children = (TransactionId *) palloc(nchildren * sizeof(TransactionId));
- *ptr = children;
-
- foreach(p, s->childXids)
- {
- TransactionId child = lfirst_xid(p);
-
- *children++ = child;
- }
+ else
+ *ptr = s->childXids;
- return nchildren;
+ return s->nChildXids;
}
/*
projects / postgresql / blobdiff