Finish disabling reduced-lock-levels-for-DDL feature.

Previous patch only covered the ALTER TABLE changes, not changes in other
commands; and it neglected to revert the documentation changes.

1 files changed, 11 insertions, 6 deletions

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 142419f2cca..4d4d4069ee8 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -3409,14 +3409,12 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 				Relation	refrel;
 
 				if (rel == NULL)
+				{
 					/* Long since locked, no need for another */
 					rel = heap_open(tab->relid, NoLock);
+				}
 
-				/*
-				 * We're adding a trigger to both tables, so the lock level
-				 * here should sensibly reflect that.
-				 */
-				refrel = heap_open(con->refrelid, ShareRowExclusiveLock);
+				refrel = heap_open(con->refrelid, RowShareLock);
 
 				validateForeignKeyConstraint(fkconstraint->conname, rel, refrel,
 											 con->refindid,
@@ -5508,7 +5506,14 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 	Oid			indexOid;
 	Oid			constrOid;
 
-	pkrel = heap_openrv(fkconstraint->pktable, lockmode);
+	/*
+	 * Grab an exclusive lock on the pk table, so that someone doesn't delete
+	 * rows out from under us. (Although a lesser lock would do for that
+	 * purpose, we'll need exclusive lock anyway to add triggers to the pk
+	 * table; trying to start with a lesser lock will just create a risk of
+	 * deadlock.)
+	 */
+	pkrel = heap_openrv(fkconstraint->pktable, AccessExclusiveLock);
 
 	/*
 	 * Validity checks (permission checks wait till we have the column