3 files changed, 40 insertions, 6 deletions

diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index 72c8e9e0c48..a1e6ea2a356 100644
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -177,7 +177,12 @@ static int	maxSharedInvalidMessagesArray;
 
 /*
  * Dynamically-registered callback functions.  Current implementation
- * assumes there won't be very many of these at once; could improve if needed.
+ * assumes there won't be enough of these to justify a dynamically resizable
+ * array; it'd be easy to improve that if needed.
+ *
+ * To avoid searching in CallSyscacheCallbacks, all callbacks for a given
+ * syscache are linked into a list pointed to by syscache_callback_links[id].
+ * The link values are syscache_callback_list[] index plus 1, or 0 for none.
  */
 
 #define MAX_SYSCACHE_CALLBACKS 64
@@ -186,10 +191,13 @@ static int	maxSharedInvalidMessagesArray;
 static struct SYSCACHECALLBACK
 {
 	int16		id;				/* cache number */
+	int16		link;			/* next callback index+1 for same cache */
 	SyscacheCallbackFunction function;
 	Datum		arg;
 }	syscache_callback_list[MAX_SYSCACHE_CALLBACKS];
 
+static int16 syscache_callback_links[SysCacheSize];
+
 static int	syscache_callback_count = 0;
 
 static struct RELCACHECALLBACK
@@ -1383,10 +1391,28 @@ CacheRegisterSyscacheCallback(int cacheid,
 							  SyscacheCallbackFunction func,
 							  Datum arg)
 {
+	if (cacheid < 0 || cacheid >= SysCacheSize)
+		elog(FATAL, "invalid cache ID: %d", cacheid);
 	if (syscache_callback_count >= MAX_SYSCACHE_CALLBACKS)
 		elog(FATAL, "out of syscache_callback_list slots");
 
+	if (syscache_callback_links[cacheid] == 0)
+	{
+		/* first callback for this cache */
+		syscache_callback_links[cacheid] = syscache_callback_count + 1;
+	}
+	else
+	{
+		/* add to end of chain, so that older callbacks are called first */
+		int			i = syscache_callback_links[cacheid] - 1;
+
+		while (syscache_callback_list[i].link > 0)
+			i = syscache_callback_list[i].link - 1;
+		syscache_callback_list[i].link = syscache_callback_count + 1;
+	}
+
 	syscache_callback_list[syscache_callback_count].id = cacheid;
+	syscache_callback_list[syscache_callback_count].link = 0;
 	syscache_callback_list[syscache_callback_count].function = func;
 	syscache_callback_list[syscache_callback_count].arg = arg;
 
@@ -1426,11 +1452,16 @@ CallSyscacheCallbacks(int cacheid, uint32 hashvalue)
 {
 	int			i;
 
-	for (i = 0; i < syscache_callback_count; i++)
+	if (cacheid < 0 || cacheid >= SysCacheSize)
+		elog(ERROR, "invalid cache ID: %d", cacheid);
+
+	i = syscache_callback_links[cacheid] - 1;
+	while (i >= 0)
 	{
 		struct SYSCACHECALLBACK *ccitem = syscache_callback_list + i;
 
-		if (ccitem->id == cacheid)
-			(*ccitem->function) (ccitem->arg, cacheid, hashvalue);
+		Assert(ccitem->id == cacheid);
+		(*ccitem->function) (ccitem->arg, cacheid, hashvalue);
+		i = ccitem->link - 1;
 	}
 }
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 066ce728775..f0a16e309c0 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -971,8 +971,6 @@ static const struct cachedesc cacheinfo[] = {
 	}
 };
 
-#define SysCacheSize	((int) lengthof(cacheinfo))
-
 static CatCache *SysCache[SysCacheSize];
 
 static bool CacheInitialized = false;
@@ -1003,6 +1001,9 @@ InitCatalogCache(void)
 	int			i,
 				j;
 
+	StaticAssertStmt(SysCacheSize == (int) lengthof(cacheinfo),
+					 "SysCacheSize does not match syscache.c's array");
+
 	Assert(!CacheInitialized);
 
 	SysCacheRelationOidSize = SysCacheSupportingRelOidSize = 0;
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index 73991dde4f9..e20284d0615 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -108,6 +108,8 @@ enum SysCacheIdentifier
 	TYPEOID,
 	USERMAPPINGOID,
 	USERMAPPINGUSERSERVER
+
+#define SysCacheSize (USERMAPPINGUSERSERVER + 1)
 };
 
 extern void InitCatalogCache(void);