From c4e0c113b8f7069be6a866a25f121611908fd07c Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 15 Apr 2002 07:54:37 +0000
Subject: [PATCH] Fix text_substr bug intrduced in 7.3 development using Joe
 Conway's patches (submitted at pgsql-patches on 2002/04/08)  + small fix.

---
 src/backend/utils/adt/varlena.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 0cd38a76be..2007e78910 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.82 2002/04/03 05:39:32 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v 1.83 2002/04/15 07:54:37 ishii Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -373,7 +373,10 @@ text_substr(PG_FUNCTION_ARGS)
 	if (eml > 1)
 	{
 		sm = 0;
-		sn = (m + n) * eml + 3; /* +3 to avoid mb characters overhanging slice end */
+		if (n > -1)
+			sn = (m + n) * eml + 3; /* +3 to avoid mb characters overhanging slice end */
+		else
+			sn = n;		/* n < 0 is special-cased by heap_tuple_untoast_attr_slice */
 	}
 #endif 
 
@@ -387,7 +390,10 @@ text_substr(PG_FUNCTION_ARGS)
 	PG_RETURN_NULL();   /* notreached: suppress compiler warning */
 #endif
 #ifdef MULTIBYTE
-	len = pg_mbstrlen_with_len (VARDATA (string), sn - 3);
+	if (n > -1)
+		len = pg_mbstrlen_with_len (VARDATA (string), sn - 3);
+	else	/* n < 0 is special-cased; need full string length */
+		len = pg_mbstrlen_with_len (VARDATA (string), VARSIZE(string)-VARHDRSZ);
 
 	if (m > len)
 	{
-- 
2.40.0