simplify_hash_bitmap_info_v2.patch

diff --git a/contrib/pageinspect/expected/hash.out b/contrib/pageinspect/expected/hash.out
index 7eb1537..fb0caee 100644
--- a/contrib/pageinspect/expected/hash.out
+++ b/contrib/pageinspect/expected/hash.out
@@ -30,23 +30,21 @@ hash_page_type | bitmap
 SELECT hash_page_type(get_raw_page('test_hash_a_idx', 6));
 ERROR:  block number 6 is out of range for relation "test_hash_a_idx"
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 0);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000008.
+ERROR:  invalid overflow block number 0
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 1);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000002.
+ERROR:  invalid overflow block number 1
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 2);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000002.
+ERROR:  invalid overflow block number 2
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 3);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000002.
+ERROR:  invalid overflow block number 3
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 4);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000002.
+ERROR:  invalid overflow block number 4
 SELECT * FROM hash_bitmap_info('test_hash_a_idx', 5);
-ERROR:  page is not an overflow page
-DETAIL:  Expected 00000001, got 00000004.
+-[ RECORD 1 ]--
+bitmapblkno | 5
+bitmapbit   | 0
+bitstatus   | t
+
 SELECT magic, version, ntuples, bsize, bmsize, bmshift, maxbucket, highmask,
 lowmask, ovflpoint, firstfree, nmaps, procid, spares, mapp FROM
 hash_metapage_info(get_raw_page('test_hash_a_idx', 0));
diff --git a/contrib/pageinspect/hashfuncs.c b/contrib/pageinspect/hashfuncs.c
index 08663c1..af25506 100644
--- a/contrib/pageinspect/hashfuncs.c
+++ b/contrib/pageinspect/hashfuncs.c
@@ -170,6 +170,45 @@ GetHashPageStatistics(Page page, HashPageStat * stat)
 	stat->free_size = PageGetFreeSpace(page);
 }
 
+/*
+ * _hash_ovflblkno_to_bitno
+ *
+ * Convert overflow page block number to bit number for free-page bitmap.
+ * We already have similar function defined in hashovfl.c but which does
+ * return value for some of the bucket pages along with overflow and bit-
+ * map pages and it is seems to be buggy to me. This function has been
+ * designed such that it only returns the value for overflow and bitmap
+ * pages.
+ */
+static uint32
+_hash_ovflblkno_to_bitno(HashMetaPage metap, BlockNumber ovflblkno)
+{
+	uint32		splitnum = metap->hashm_ovflpoint;
+	uint32		i;
+	uint32		bitnum;
+
+	/* Determine the split number containing this page */
+	for (i = 1; i <= splitnum; i++)
+	{
+		if (ovflblkno <= (BlockNumber) (1 << i))
+			break;				/* oops */
+		bitnum = ovflblkno - (1 << i);
+		/*
+		 * bitnum has to be greater than number of overflow
+		 * page added in previous split point. The overflow
+		 * page at this splitnum (i) if any should start from
+		 * ((2 ^ i) + metap->hashm_spares[i -1] + 1).
+		 */
+		if (bitnum > metap->hashm_spares[i -1] &&
+			bitnum <= metap->hashm_spares[i])
+			return bitnum - 1;	/* -1 to convert 1-based to 0-based */
+	}
+
+	elog(ERROR, "invalid overflow block number %u", ovflblkno);
+	return 0;					/* keep compiler quiet */
+}
+
+
 /* ---------------------------------------------------
  * hash_page_type()
  *
@@ -380,12 +419,11 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 	Oid			indexRelid = PG_GETARG_OID(0);
 	uint64		ovflblkno = PG_GETARG_INT64(1);
 	HashMetaPage metap;
-	Buffer		buf,
-				metabuf;
+	Buffer		metabuf,
+				mapbuf;
 	BlockNumber bitmapblkno;
-	Page		page;
+	Page		mappage;
 	bool		bit = false;
-	HashPageOpaque	opaque;
 	TupleDesc	tupleDesc;
 	Relation	indexRel;
 	uint32		ovflbitno;
@@ -395,6 +433,7 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 	int			j;
 	Datum		values[3];
 	bool		nulls[3];
+	uint32		*freep = NULL;
 
 	if (!superuser())
 		ereport(ERROR,
@@ -418,25 +457,6 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 				 errmsg("block number " UINT64_FORMAT " is out of range for relation \"%s\"",
 						ovflblkno, RelationGetRelationName(indexRel))));
 
-	buf = ReadBufferExtended(indexRel, MAIN_FORKNUM, (BlockNumber) ovflblkno,
-							 RBM_NORMAL, NULL);
-	LockBuffer(buf, BUFFER_LOCK_SHARE);
-	_hash_checkpage(indexRel, buf, LH_PAGE_TYPE);
-	page = BufferGetPage(buf);
-	opaque = (HashPageOpaque) PageGetSpecialPointer(page);
-
-	if (opaque->hasho_flag != LH_OVERFLOW_PAGE)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("page is not an overflow page"),
-				 errdetail("Expected %08x, got %08x.",
-							LH_OVERFLOW_PAGE, opaque->hasho_flag)));
-
-	if (BlockNumberIsValid(opaque->hasho_prevblkno))
-		bit = true;
-
-	UnlockReleaseBuffer(buf);
-
 	/* Read the metapage so we can determine which bitmap page to use */
 	metabuf = _hash_getbuf(indexRel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);
 	metap = HashPageGetMeta(BufferGetPage(metabuf));
@@ -456,6 +476,14 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 
 	_hash_relbuf(indexRel, metabuf);
 
+	/* Check the status of bitmap bit for overflow page */
+	mapbuf = _hash_getbuf(indexRel, bitmapblkno, HASH_READ, LH_BITMAP_PAGE);
+	mappage = BufferGetPage(mapbuf);
+	freep = HashPageGetBitmap(mappage);
+
+	bit = ISSET(freep, bitmapbit) != 0;
+
+	_hash_relbuf(indexRel, mapbuf);
 	index_close(indexRel, AccessShareLock);
 
 	/* Build a tuple descriptor for our result type */
diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c
index 753c8a6..e8928ef 100644
--- a/src/backend/access/hash/hashovfl.c
+++ b/src/backend/access/hash/hashovfl.c
@@ -52,12 +52,10 @@ bitno_to_blkno(HashMetaPage metap, uint32 ovflbitnum)
 }
 
 /*
- * _hash_ovflblkno_to_bitno
- *
  * Convert overflow page block number to bit number for free-page bitmap.
  */
-uint32
-_hash_ovflblkno_to_bitno(HashMetaPage metap, BlockNumber ovflblkno)
+static uint32
+blkno_to_bitno(HashMetaPage metap, BlockNumber ovflblkno)
 {
 	uint32		splitnum = metap->hashm_ovflpoint;
 	uint32		i;
@@ -487,7 +485,7 @@ _hash_freeovflpage(Relation rel, Buffer ovflbuf, Buffer wbuf,
 	metap = HashPageGetMeta(BufferGetPage(metabuf));
 
 	/* Identify which bit to set */
-	ovflbitno = _hash_ovflblkno_to_bitno(metap, ovflblkno);
+	ovflbitno = blkno_to_bitno(metap, ovflblkno);
 
 	bitmappage = ovflbitno >> BMPG_SHIFT(metap);
 	bitmapbit = ovflbitno & BMPG_MASK(metap);
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index c045585..acbe0ea 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -313,7 +313,6 @@ extern void _hash_squeezebucket(Relation rel,
 					Bucket bucket, BlockNumber bucket_blkno,
 					Buffer bucket_buf,
 					BufferAccessStrategy bstrategy);
-extern uint32 _hash_ovflblkno_to_bitno(HashMetaPage metap, BlockNumber ovflblkno);
 
 /* hashpage.c */
 extern Buffer _hash_getbuf(Relation rel, BlockNumber blkno,