From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 17 Dec 2019 20:53:17 +0000 (-0500)
Subject: Fix bad formula in previous commit.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=5184f110aa4130ec87b0b3e0834292cd8cb1fd8a;p=users%2Frhaas%2Fpostgres.git

Fix bad formula in previous commit.

Commit d5406dea25b600408e7acf17d5a06e82d3ce6d0d used a slightly
novel, and wrong, approach to compute the length of the last
toast chunk. It worked fine unless the last chunk happened to
have the largest possible size.
---

diff --git a/src/backend/access/common/detoast.c b/src/backend/access/common/detoast.c
index 61d7e64c44..6341107e88 100644
--- a/src/backend/access/common/detoast.c
+++ b/src/backend/access/common/detoast.c
@@ -443,7 +443,7 @@ toast_fetch_datum(struct varlena *attr)
 									 toast_pointer.va_valueid,
 									 RelationGetRelationName(toastrel))));
 		expected_size = curchunk < totalchunks - 1 ? TOAST_MAX_CHUNK_SIZE
-			: attrsize % TOAST_MAX_CHUNK_SIZE;
+			: attrsize - ((totalchunks - 1) * TOAST_MAX_CHUNK_SIZE);
 		if (chunksize != expected_size)
 			ereport(ERROR,
 					(errcode(ERRCODE_DATA_CORRUPTED),
@@ -676,7 +676,7 @@ toast_fetch_datum_slice(struct varlena *attr, int32 sliceoffset,
 									 toast_pointer.va_valueid,
 									 RelationGetRelationName(toastrel))));
 		expected_size = curchunk < totalchunks - 1 ? TOAST_MAX_CHUNK_SIZE
-			: attrsize % TOAST_MAX_CHUNK_SIZE;
+			: attrsize - ((totalchunks - 1) * TOAST_MAX_CHUNK_SIZE);
 		if (chunksize != expected_size)
 			ereport(ERROR,
 					(errcode(ERRCODE_DATA_CORRUPTED),