From 7be8946c78935f20faf17f8e313c4b86cb773967 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 23 Jul 2010 00:43:00 +0000
Subject: [PATCH] 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 | 28 +++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index d125738b4c8..7bb7804dabb 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 1.293 2010/07/06 19:18:55 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.294 2010/07/23 00:43:00 rhaas Exp $
*
*-------------------------------------------------------------------------
*/
@@ -408,10 +408,32 @@ AssignTransactionId(TransactionState s)
/*
* Ensure parent(s) have XIDs, so that a child always has an XID later
- * than its parent.
+ * 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 (isSubXact && !TransactionIdIsValid(s->parent->transactionId))
- AssignTransactionId(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)
+ AssignTransactionId(parents[--parentOffset]);
+
+ pfree(parents);
+ }
/*
* Generate a new Xid and record it in PG_PROC and pg_subtrans.
--
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