Consolidate nbtree VACUUM metapage routines.

Simplify _bt_vacuum_needs_cleanup() functions's signature (it only needs
a single 'rel' argument now), and move it next to its sibling function
in nbtpage.c.

I believe that _bt_vacuum_needs_cleanup() was originally located in
nbtree.c due to an include dependency issue.  That's no longer an issue.

Follow-up to commit 9f3665f.

Author: petergeoghegan

src/backend/access/nbtree/nbtpage.c

@@ -168,15 +168,67 @@ _bt_getmeta(Relation rel, Buffer metabuf)
 }
 
 /*
- *	_bt_set_cleanup_info() -- Update metapage for btvacuumcleanup().
+ * _bt_vacuum_needs_cleanup() -- Checks if index needs cleanup
  *
- *		This routine is called at the end of each VACUUM's btvacuumcleanup()
- *		call.  Its purpose is to maintain the metapage fields that are used by
- *		_bt_vacuum_needs_cleanup() to decide whether or not a btvacuumscan()
- *		call should go ahead for an entire VACUUM operation.
+ * Called by btvacuumcleanup when btbulkdelete was never called because no
+ * index tuples needed to be deleted.
+ */
+bool
+_bt_vacuum_needs_cleanup(Relation rel)
+{
+	Buffer		metabuf;
+	Page		metapg;
+	BTMetaPageData *metad;
+	uint32		btm_version;
+	BlockNumber prev_num_delpages;
+
+	/*
+	 * Copy details from metapage to local variables quickly.
+	 *
+	 * Note that we deliberately avoid using cached version of metapage here.
+	 */
+	metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_READ);
+	metapg = BufferGetPage(metabuf);
+	metad = BTPageGetMeta(metapg);
+	btm_version = metad->btm_version;
+
+	if (btm_version < BTREE_NOVAC_VERSION)
+	{
+		/*
+		 * Metapage needs to be dynamically upgraded to store fields that are
+		 * only present when btm_version >= BTREE_NOVAC_VERSION
+		 */
+		_bt_relbuf(rel, metabuf);
+		return true;
+	}
+
+	prev_num_delpages = metad->btm_last_cleanup_num_delpages;
+	_bt_relbuf(rel, metabuf);
+
+	/*
+	 * Trigger cleanup in rare cases where prev_num_delpages exceeds 5% of the
+	 * total size of the index.  We can reasonably expect (though are not
+	 * guaranteed) to be able to recycle this many pages if we decide to do a
+	 * btvacuumscan call during the ongoing btvacuumcleanup.
+	 *
+	 * Our approach won't reliably avoid "wasted" cleanup-only btvacuumscan
+	 * calls.  That is, we can end up scanning the entire index without ever
+	 * placing even 1 of the prev_num_delpages pages in the free space map, at
+	 * least in certain narrow cases (see nbtree/README section on recycling
+	 * deleted pages for details).  This rarely comes up in practice.
+	 */
+	if (prev_num_delpages > 0 &&
+		prev_num_delpages > RelationGetNumberOfBlocks(rel) / 20)
+		return true;
+
+	return false;
+}
+
+/*
+ * _bt_set_cleanup_info() -- Update metapage for btvacuumcleanup.
  *
- *		See btvacuumcleanup() and _bt_vacuum_needs_cleanup() for the
- *		definition of num_delpages.
+ * Called at the end of btvacuumcleanup, when num_delpages value has been
+ * finalized.
  */
 void
 _bt_set_cleanup_info(Relation rel, BlockNumber num_delpages)

src/backend/access/nbtree/nbtree.c

@@ -773,67 +773,6 @@ _bt_parallel_advance_array_keys(IndexScanDesc scan)
 	SpinLockRelease(&btscan->btps_mutex);
 }
 
-/*
- * _bt_vacuum_needs_cleanup() -- Checks if index needs cleanup
- *
- * Called by btvacuumcleanup when btbulkdelete was never called because no
- * tuples needed to be deleted by VACUUM.
- *
- * When we return false, VACUUM can even skip the cleanup-only call to
- * btvacuumscan (i.e. there will be no btvacuumscan call for this index at
- * all).  Otherwise, a cleanup-only btvacuumscan call is required.
- */
-static bool
-_bt_vacuum_needs_cleanup(IndexVacuumInfo *info)
-{
-	Buffer		metabuf;
-	Page		metapg;
-	BTMetaPageData *metad;
-	uint32		btm_version;
-	BlockNumber prev_num_delpages;
-
-	/*
-	 * Copy details from metapage to local variables quickly.
-	 *
-	 * Note that we deliberately avoid using cached version of metapage here.
-	 */
-	metabuf = _bt_getbuf(info->index, BTREE_METAPAGE, BT_READ);
-	metapg = BufferGetPage(metabuf);
-	metad = BTPageGetMeta(metapg);
-	btm_version = metad->btm_version;
-
-	if (btm_version < BTREE_NOVAC_VERSION)
-	{
-		/*
-		 * Metapage needs to be dynamically upgraded to store fields that are
-		 * only present when btm_version >= BTREE_NOVAC_VERSION
-		 */
-		_bt_relbuf(info->index, metabuf);
-		return true;
-	}
-
-	prev_num_delpages = metad->btm_last_cleanup_num_delpages;
-	_bt_relbuf(info->index, metabuf);
-
-	/*
-	 * Trigger cleanup in rare cases where prev_num_delpages exceeds 5% of the
-	 * total size of the index.  We can reasonably expect (though are not
-	 * guaranteed) to be able to recycle this many pages if we decide to do a
-	 * btvacuumscan call during the ongoing btvacuumcleanup.
-	 *
-	 * Our approach won't reliably avoid "wasted" cleanup-only btvacuumscan
-	 * calls.  That is, we can end up scanning the entire index without ever
-	 * placing even 1 of the prev_num_delpages pages in the free space map, at
-	 * least in certain narrow cases (see nbtree/README section on recycling
-	 * deleted pages for details).  This rarely comes up in practice.
-	 */
-	if (prev_num_delpages > 0 &&
-		prev_num_delpages > RelationGetNumberOfBlocks(info->index) / 20)
-		return true;
-
-	return false;
-}
-
 /*
  * Bulk deletion of all index entries pointing to a set of heap tuples.
  * The set of target tuples is specified via a callback routine that tells
@@ -894,7 +833,7 @@ btvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 	if (stats == NULL)
 	{
 		/* Check if VACUUM operation can entirely avoid btvacuumscan() call */
-		if (!_bt_vacuum_needs_cleanup(info))
+		if (!_bt_vacuum_needs_cleanup(info->index))
 			return NULL;
 
 		/*

src/include/access/nbtree.h

@@ -1170,6 +1170,7 @@ extern OffsetNumber _bt_findsplitloc(Relation rel, Page origpage,
  */
 extern void _bt_initmetapage(Page page, BlockNumber rootbknum, uint32 level,
 							 bool allequalimage);
+extern bool _bt_vacuum_needs_cleanup(Relation rel);
 extern void _bt_set_cleanup_info(Relation rel, BlockNumber num_delpages);
 extern void _bt_upgrademetapage(Page page);
 extern Buffer _bt_getroot(Relation rel, int access);