From 871dd024a6adf7766702b1cdacfb02bd8002d2bb Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 28 Nov 2011 19:12:17 -0500
Subject: [PATCH] Disallow deletion of CurrentExtensionObject while running
extension script.
While the deletion in itself wouldn't break things, any further creation
of objects in the script would result in dangling pg_depend entries being
added by recordDependencyOnCurrentExtension(). An example from Phil
Sorber convinced me that this is just barely likely enough to be worth
expending a couple lines of code to defend against. The resulting error
message might be confusing, but it's better than leaving corrupted catalog
contents for the user to deal with.
---
src/backend/commands/extension.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index c334ca9cf8c..7192c458e75 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -1577,6 +1577,23 @@ RemoveExtensionById(Oid extId)
HeapTuple tuple;
ScanKeyData entry[1];
+ /*
+ * Disallow deletion of any extension that's currently open for insertion;
+ * else subsequent executions of recordDependencyOnCurrentExtension()
+ * could create dangling pg_depend records that refer to a no-longer-valid
+ * pg_extension OID. This is needed not so much because we think people
+ * might write "DROP EXTENSION foo" in foo's own script files, as because
+ * errors in dependency management in extension script files could give
+ * rise to cases where an extension is dropped as a result of recursing
+ * from some contained object. Because of that, we must test for the case
+ * here, not at some higher level of the DROP EXTENSION command.
+ */
+ if (extId == CurrentExtensionObject)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("cannot drop extension \"%s\" because it is being modified",
+ get_extension_name(extId))));
+
rel = heap_open(ExtensionRelationId, RowExclusiveLock);
ScanKeyInit(&entry[0],
--
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