From e75b0d02cf039858a9d837fbdb7cd1ce1cf279d9 Mon Sep 17 00:00:00 2001
From: "Chao Li (Evan)" <lic@highgo.com>
Date: Thu, 15 Oct 2026 17:02:23 +0800
Subject: [PATCH v1] Avoid repeated scans of the output buffer in
 oidvectortypes()

Track the end of the output buffer and append directly to it instead of
using strcat(), which rescans the accumulated string for each type name.
This avoids quadratic scanning for large input vectors.

Also check for interrupts in the loop and free temporary type names
after copying them into the result.

Author: Chao Li <lic@highgo.com>
---
 src/backend/utils/adt/format_type.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/backend/utils/adt/format_type.c b/src/backend/utils/adt/format_type.c
index 7a5695c6245..d5d5f460bb3 100644
--- a/src/backend/utils/adt/format_type.c
+++ b/src/backend/utils/adt/format_type.c
@@ -21,6 +21,7 @@
 #include "catalog/namespace.h"
 #include "catalog/pg_type.h"
 #include "mb/pg_wchar.h"
+#include "miscadmin.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
@@ -448,6 +449,7 @@ oidvectortypes(PG_FUNCTION_ARGS)
 {
 	oidvector  *oidArray = (oidvector *) PG_GETARG_POINTER(0);
 	char	   *result;
+	char	   *end;
 	int			numargs;
 	int			num;
 	size_t		total;
@@ -460,29 +462,42 @@ oidvectortypes(PG_FUNCTION_ARGS)
 	total = 20 * numargs + 1;
 	result = palloc(total);
 	result[0] = '\0';
+	end = result;
 	left = total - 1;
 
 	for (num = 0; num < numargs; num++)
 	{
-		char	   *typename = format_type_extended(oidArray->values[num], -1,
-													FORMAT_TYPE_ALLOW_INVALID);
-		size_t		slen = strlen(typename);
+		char	   *typename;
+		size_t		slen;
+
+		CHECK_FOR_INTERRUPTS();
+
+		typename = format_type_extended(oidArray->values[num], -1,
+										FORMAT_TYPE_ALLOW_INVALID);
+		slen = strlen(typename);
 
 		if (left < (slen + 2))
 		{
+			size_t		used = end - result;
+
 			total += slen + 2;
 			result = repalloc(result, total);
+			end = result + used;
 			left += slen + 2;
 		}
 
 		if (num > 0)
 		{
-			strcat(result, ", ");
+			memcpy(end, ", ", 2);
+			end += 2;
 			left -= 2;
 		}
-		strcat(result, typename);
+		memcpy(end, typename, slen);
+		end += slen;
 		left -= slen;
+		pfree(typename);
 	}
+	*end = '\0';
 
 	PG_RETURN_TEXT_P(cstring_to_text(result));
 }
-- 
2.50.1 (Apple Git-155)