Check block number against the correct fork in get_raw_page().

get_raw_page tried to validate the supplied block number against
RelationGetNumberOfBlocks(), which of course is only right when
accessing the main fork.  In most cases, the main fork is longer
than the others, so that the check was too weak (allowing a
lower-level error to be reported, but no real harm to be done).
However, very small tables could have an FSM larger than their heap,
in which case the mistake prevented access to some FSM pages.
Per report from Torsten Foertsch.

In passing, make the bad-block-number error into an ereport not elog
(since it's certainly not an internal error); and fix sloppily
maintained comment for RelationGetNumberOfBlocksInFork.

This has been wrong since we invented relation forks, so back-patch
to all supported branches.

diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c
index e3ffaf4e4f26c6dfaa4a438eba95de31061641b4..154d68969ee338c9aad2118ca8800646a00716b6 100644 (file)
--- a/contrib/pageinspect/rawpage.c
+++ b/contrib/pageinspect/rawpage.c
@@ -133,9 +133,11 @@ get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno)
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot access temporary tables of other sessions")));
 
-   if (blkno >= RelationGetNumberOfBlocks(rel))
-       elog(ERROR, "block number %u is out of range for relation \"%s\"",
-            blkno, RelationGetRelationName(rel));
+   if (blkno >= RelationGetNumberOfBlocksInFork(rel, forknum))
+       ereport(ERROR,
+               (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                errmsg("block number %u is out of range for relation \"%s\"",
+                       blkno, RelationGetRelationName(rel))));
 
    /* Initialize buffer to copy to */
    raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 0f593b209409021f9c8a2ccbf925b0b5786cd0dd..945e9f367c46dd57d0affa65885f52e3603081c9 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2033,8 +2033,8 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 }
 
 /*
- * RelationGetNumberOfBlocks
- *     Determines the current number of pages in the relation.
+ * RelationGetNumberOfBlocksInFork
+ *     Determines the current number of pages in the specified relation fork.
  */
 BlockNumber
 RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)