Minor code-cleanliness improvements for btree.

Make the btree page-flags test macros (P_ISLEAF and friends) return clean
boolean values, rather than values that might not fit in a bool.  Use them
in a few places that were randomly referencing the flag bits directly.

In passing, change access/nbtree/'s only direct use of BUFFER_LOCK_SHARE to
BT_READ.  (Some think we should go the other way, but as long as we have
BT_READ/BT_WRITE, let's use them consistently.)

Masahiko Sawada, reviewed by Doug Doole

Discussion: https://postgr.es/m/CAD21AoBmWPeN=WBB5Jvyz_Nt3rmW1ebUyAnk3ZbJP3RMXALJog@mail.gmail.com

Author: tglsfdc

contrib/amcheck/verify_nbtree.c

@@ -1195,7 +1195,7 @@ palloc_btree_page(BtreeCheckState *state, BlockNumber blocknum)
 
 	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 
-	if (opaque->btpo_flags & BTP_META && blocknum != BTREE_METAPAGE)
+	if (P_ISMETA(opaque) && blocknum != BTREE_METAPAGE)
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
 				 errmsg("invalid meta page found at block %u in index \"%s\"",
@@ -1206,7 +1206,7 @@ palloc_btree_page(BtreeCheckState *state, BlockNumber blocknum)
 	{
 		BTMetaPageData *metad = BTPageGetMeta(page);
 
-		if (!(opaque->btpo_flags & BTP_META) ||
+		if (!P_ISMETA(opaque) ||
 			metad->btm_magic != BTREE_MAGIC)
 			ereport(ERROR,
 					(errcode(ERRCODE_INDEX_CORRUPTED),

contrib/pgstattuple/pgstattuple.c

@@ -416,7 +416,7 @@ pgstat_btree_page(pgstattuple_type *stat, Relation rel, BlockNumber blkno,
 		BTPageOpaque opaque;
 
 		opaque = (BTPageOpaque) PageGetSpecialPointer(page);
-		if (opaque->btpo_flags & (BTP_DELETED | BTP_HALF_DEAD))
+		if (P_IGNORE(opaque))
 		{
 			/* recyclable page */
 			stat->free_space += BLCKSZ;

src/backend/access/nbtree/nbtpage.c

@@ -162,7 +162,7 @@ _bt_getroot(Relation rel, int access)
 	metad = BTPageGetMeta(metapg);
 
 	/* sanity-check the metapage */
-	if (!(metaopaque->btpo_flags & BTP_META) ||
+	if (!P_ISMETA(metaopaque) ||
 		metad->btm_magic != BTREE_MAGIC)
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
@@ -365,7 +365,7 @@ _bt_gettrueroot(Relation rel)
 	metaopaque = (BTPageOpaque) PageGetSpecialPointer(metapg);
 	metad = BTPageGetMeta(metapg);
 
-	if (!(metaopaque->btpo_flags & BTP_META) ||
+	if (!P_ISMETA(metaopaque) ||
 		metad->btm_magic != BTREE_MAGIC)
 		ereport(ERROR,
 				(errcode(ERRCODE_INDEX_CORRUPTED),
@@ -452,7 +452,7 @@ _bt_getrootheight(Relation rel)
 		metad = BTPageGetMeta(metapg);
 
 		/* sanity-check the metapage */
-		if (!(metaopaque->btpo_flags & BTP_META) ||
+		if (!P_ISMETA(metaopaque) ||
 			metad->btm_magic != BTREE_MAGIC)
 			ereport(ERROR,
 					(errcode(ERRCODE_INDEX_CORRUPTED),

src/backend/access/nbtree/nbtxlog.c

@@ -135,7 +135,7 @@ _bt_clear_incomplete_split(XLogReaderState *record, uint8 block_id)
 		Page		page = (Page) BufferGetPage(buf);
 		BTPageOpaque pageop = (BTPageOpaque) PageGetSpecialPointer(page);
 
-		Assert((pageop->btpo_flags & BTP_INCOMPLETE_SPLIT) != 0);
+		Assert(P_INCOMPLETE_SPLIT(pageop));
 		pageop->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
 
 		PageSetLSN(page, lsn);
@@ -598,7 +598,7 @@ btree_xlog_delete_get_latestRemovedXid(XLogReaderState *record)
 			UnlockReleaseBuffer(ibuffer);
 			return InvalidTransactionId;
 		}
-		LockBuffer(hbuffer, BUFFER_LOCK_SHARE);
+		LockBuffer(hbuffer, BT_READ);
 		hpage = (Page) BufferGetPage(hbuffer);
 
 		/*

src/include/access/nbtree.h

@@ -173,14 +173,14 @@ typedef struct BTMetaPageData
  */
 #define P_LEFTMOST(opaque)		((opaque)->btpo_prev == P_NONE)
 #define P_RIGHTMOST(opaque)		((opaque)->btpo_next == P_NONE)
-#define P_ISLEAF(opaque)		((opaque)->btpo_flags & BTP_LEAF)
-#define P_ISROOT(opaque)		((opaque)->btpo_flags & BTP_ROOT)
-#define P_ISDELETED(opaque)		((opaque)->btpo_flags & BTP_DELETED)
-#define P_ISMETA(opaque)		((opaque)->btpo_flags & BTP_META)
-#define P_ISHALFDEAD(opaque)	((opaque)->btpo_flags & BTP_HALF_DEAD)
-#define P_IGNORE(opaque)		((opaque)->btpo_flags & (BTP_DELETED|BTP_HALF_DEAD))
-#define P_HAS_GARBAGE(opaque)	((opaque)->btpo_flags & BTP_HAS_GARBAGE)
-#define P_INCOMPLETE_SPLIT(opaque)	((opaque)->btpo_flags & BTP_INCOMPLETE_SPLIT)
+#define P_ISLEAF(opaque)		(((opaque)->btpo_flags & BTP_LEAF) != 0)
+#define P_ISROOT(opaque)		(((opaque)->btpo_flags & BTP_ROOT) != 0)
+#define P_ISDELETED(opaque)		(((opaque)->btpo_flags & BTP_DELETED) != 0)
+#define P_ISMETA(opaque)		(((opaque)->btpo_flags & BTP_META) != 0)
+#define P_ISHALFDEAD(opaque)	(((opaque)->btpo_flags & BTP_HALF_DEAD) != 0)
+#define P_IGNORE(opaque)		(((opaque)->btpo_flags & (BTP_DELETED|BTP_HALF_DEAD)) != 0)
+#define P_HAS_GARBAGE(opaque)	(((opaque)->btpo_flags & BTP_HAS_GARBAGE) != 0)
+#define P_INCOMPLETE_SPLIT(opaque)	(((opaque)->btpo_flags & BTP_INCOMPLETE_SPLIT) != 0)
 
 /*
  *	Lehman and Yao's algorithm requires a ``high key'' on every non-rightmost