From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 2 Aug 2026 20:49:17 +0000 (-0400)
Subject: Tighten up TS dictionary cache entry creation.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;ds=inline;p=thirdparty%2Fpostgresql.git

Tighten up TS dictionary cache entry creation.

In the not-too-likely scenario where we successfully created a hash
table entry for a TS dictionary, but then failed to make a small
memory context for it, we left the hash entry in existence but with
a garbage value for dictCtx.  This confused the code the next time
through, leading to a crash.  Rearrange things so that we leave
the hash entry in a well-defined state with dictCtx == NULL, and
then the next try knows it still needs to make a memory context.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/0f3ddeb5-0dbd-479c-9d0e-ae254758e624@gmail.com
Backpatch-through: 14
---

diff --git a/src/backend/utils/cache/ts_cache.c b/src/backend/utils/cache/ts_cache.c
index 9e29f1386b0..1cec9a1f9a6 100644
--- a/src/backend/utils/cache/ts_cache.c
+++ b/src/backend/utils/cache/ts_cache.c
@@ -280,37 +280,50 @@ lookup_ts_dictionary_cache(Oid dictId)
 			elog(ERROR, "text search template %u has no lexize method",
 				 template->tmpllexize);
 
+		/*
+		 * OK, create or clear out the hashtable entry
+		 */
 		if (entry == NULL)
 		{
 			bool		found;
 
-			/* Now make the cache entry */
 			entry = (TSDictionaryCacheEntry *)
 				hash_search(TSDictionaryCacheHash,
 							&dictId,
 							HASH_ENTER, &found);
 			Assert(!found);		/* it wasn't there a moment ago */
 
-			/* Create private memory context the first time through */
+			memset(entry, 0, sizeof(TSDictionaryCacheEntry));
+			entry->dictId = dictId;
+			saveCtx = NULL;
+		}
+		else
+		{
+			saveCtx = entry->dictCtx;	/* could be NULL if we failed before */
+			memset(entry, 0, sizeof(TSDictionaryCacheEntry));
+			entry->dictId = dictId;
+			entry->dictCtx = saveCtx;
+		}
+
+		/*
+		 * Create or clear the entry's private memory context
+		 */
+		if (saveCtx == NULL)
+		{
 			saveCtx = AllocSetContextCreate(CacheMemoryContext,
 											"TS dictionary",
 											ALLOCSET_SMALL_SIZES);
+			entry->dictCtx = saveCtx;
 			MemoryContextCopyAndSetIdentifier(saveCtx, NameStr(dict->dictname));
 		}
 		else
 		{
-			/* Clear the existing entry's private context */
-			saveCtx = entry->dictCtx;
 			/* Don't let context's ident pointer dangle while we reset it */
 			MemoryContextSetIdentifier(saveCtx, NULL);
 			MemoryContextReset(saveCtx);
 			MemoryContextCopyAndSetIdentifier(saveCtx, NameStr(dict->dictname));
 		}
 
-		MemSet(entry, 0, sizeof(TSDictionaryCacheEntry));
-		entry->dictId = dictId;
-		entry->dictCtx = saveCtx;
-
 		entry->lexizeOid = template->tmpllexize;
 
 		if (OidIsValid(template->tmplinit))