3 files changed, 13 insertions, 45 deletions

diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c
index 4082103fe2d..bc791761459 100644
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -33,7 +33,6 @@
 #include "storage/predicate.h"
 #include "utils/snapmgr.h"
 
-static void _bt_cachemetadata(Relation rel, BTMetaPageData *metad);
 static bool _bt_mark_page_halfdead(Relation rel, Buffer buf, BTStack stack);
 static bool _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf,
 						 bool *rightsib_empty);
@@ -107,44 +106,6 @@ _bt_upgrademetapage(Page page)
 }
 
 /*
- * Cache metadata from meta page to rel->rd_amcache.
- */
-static void
-_bt_cachemetadata(Relation rel, BTMetaPageData *metad)
-{
-	/* We assume rel->rd_amcache was already freed by caller */
-	Assert(rel->rd_amcache == NULL);
-	rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
-										 sizeof(BTMetaPageData));
-
-	/*
-	 * Meta page should be of supported version (should be already checked by
-	 * caller).
-	 */
-	Assert(metad->btm_version >= BTREE_MIN_VERSION &&
-		   metad->btm_version <= BTREE_VERSION);
-
-	if (metad->btm_version == BTREE_VERSION)
-	{
-		/* Last version of meta-data, no need to upgrade */
-		memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
-	}
-	else
-	{
-		BTMetaPageData *cached_metad = (BTMetaPageData *) rel->rd_amcache;
-
-		/*
-		 * Upgrade meta-data: copy available information from meta-page and
-		 * fill new fields with default values.
-		 */
-		memcpy(rel->rd_amcache, metad, offsetof(BTMetaPageData, btm_oldest_btpo_xact));
-		cached_metad->btm_version = BTREE_VERSION;
-		cached_metad->btm_oldest_btpo_xact = InvalidTransactionId;
-		cached_metad->btm_last_cleanup_num_heap_tuples = -1.0;
-	}
-}
-
-/*
  *	_bt_update_meta_cleanup_info() -- Update cleanup-related information in
  *									  the metapage.
  *
@@ -442,7 +403,9 @@ _bt_getroot(Relation rel, int access)
 		/*
 		 * Cache the metapage data for next time
 		 */
-		_bt_cachemetadata(rel, metad);
+		rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
+											 sizeof(BTMetaPageData));
+		memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
 
 		/*
 		 * We are done with the metapage; arrange to release it via first
@@ -641,15 +604,18 @@ _bt_getrootheight(Relation rel)
 		/*
 		 * Cache the metapage data for next time
 		 */
-		_bt_cachemetadata(rel, metad);
-
+		rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
+											 sizeof(BTMetaPageData));
+		memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
 		_bt_relbuf(rel, metabuf);
 	}
 
+	/* Get cached page */
 	metad = (BTMetaPageData *) rel->rd_amcache;
 	/* We shouldn't have cached it if any of these fail */
 	Assert(metad->btm_magic == BTREE_MAGIC);
-	Assert(metad->btm_version == BTREE_VERSION);
+	Assert(metad->btm_version >= BTREE_MIN_VERSION);
+	Assert(metad->btm_version <= BTREE_VERSION);
 	Assert(metad->btm_fastroot != P_NONE);
 
 	return metad->btm_fastlevel;
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 67a94cb80a2..1ecdeb3fb68 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -108,6 +108,8 @@ _bt_restore_meta(XLogReaderState *record, uint8 block_id)
 	md->btm_level = xlrec->level;
 	md->btm_fastroot = xlrec->fastroot;
 	md->btm_fastlevel = xlrec->fastlevel;
+	/* Cannot log BTREE_MIN_VERSION index metapage without upgrade */
+	Assert(md->btm_version == BTREE_VERSION);
 	md->btm_oldest_btpo_xact = xlrec->oldest_btpo_xact;
 	md->btm_last_cleanup_num_heap_tuples = xlrec->last_cleanup_num_heap_tuples;
 
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index ea495f1724a..1a6678f877f 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -97,12 +97,12 @@ typedef BTPageOpaqueData *BTPageOpaque;
 typedef struct BTMetaPageData
 {
 	uint32		btm_magic;		/* should contain BTREE_MAGIC */
-	uint32		btm_version;	/* should contain BTREE_VERSION */
+	uint32		btm_version;	/* nbtree version (always <= BTREE_VERSION) */
 	BlockNumber btm_root;		/* current root location */
 	uint32		btm_level;		/* tree level of the root page */
 	BlockNumber btm_fastroot;	/* current "fast" root location */
 	uint32		btm_fastlevel;	/* tree level of the "fast" root page */
-	/* following fields are available since page version 3 */
+	/* remaining fields only valid when btm_version is BTREE_VERSION */
 	TransactionId btm_oldest_btpo_xact; /* oldest btpo_xact among all deleted
 										 * pages */
 	float8		btm_last_cleanup_num_heap_tuples;	/* number of heap tuples