postgres.git / summary / log / commit / refs

commit    ae1b65b5aa17ab96f95f34d258b1cb358f1d9030
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Fri Jul 23 00:43:35 2010 +0000
First released in: 9.1.0, 8.0.26, 8.1.22, 8.2.18, 8.3.12, 8.4.5, 9.0.0

    Avoid deep recursion when assigning XIDs to multiple levels of subxacts.
    
    Backpatch to 8.0.
    
    Andres Freund, with cleanup and adjustment for older branches by me.


 src/backend/access/transam/xact.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 583f55ddae6..0ec504d26be 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.229.2.7 2010/01/24 21:49:47 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.229.2.8 2010/07/23 00:43:35 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -351,8 +351,35 @@ AssignSubTransactionId(TransactionState s)
 
 	Assert(s->parent != NULL);
 	Assert(s->state == TRANS_INPROGRESS);
+
+	/*
+	 * Ensure parent(s) have XIDs, so that a child always has an XID later
+	 * than its parent.  Musn't recurse here, or we might get a stack overflow
+	 * if we're at the bottom of a huge stack of subtransactions none of which
+	 * have XIDs yet.
+	 */
 	if (!TransactionIdIsValid(s->parent->transactionId))
-		AssignSubTransactionId(s->parent);
+	{
+		TransactionState	p = s->parent;
+		TransactionState   *parents;
+		size_t	parentOffset = 0;
+
+		parents = palloc(sizeof(TransactionState) *  s->nestingLevel);
+		while (p != NULL && !TransactionIdIsValid(p->transactionId))
+		{
+			parents[parentOffset++] = p;
+			p = p->parent;
+		}
+
+		/*
+		 * This is technically a recursive call, but the recursion will
+		 * never be more than one layer deep.
+		 */
+		while (parentOffset != 0)
+			AssignSubTransactionId(parents[--parentOffset]);
+
+		pfree(parents);
+	}
 
 	/*
 	 * Generate a new Xid and record it in PG_PROC and pg_subtrans.


[parent: 49d7a64f6042]