Refactor PinBufferForBlock() to remove checks about persistence.

There are checks in PinBufferForBlock() function to set persistence of
the relation.  This function is called for each block in the relation.
Instead, set persistence of the relation before PinBufferForBlock().

Nazir Bilal Yavuz

Discussion: https://postgr.es/m/CAN55FZ0JKL6vk1xQp6rfOXiNFV1u1H0tJDPPGHWoiO3ea2Wc=A@mail.gmail.com

src/backend/storage/aio/read_stream.c

@@ -551,7 +551,7 @@ read_stream_begin_relation(int flags,
 	{
 		stream->ios[i].op.rel = rel;
 		stream->ios[i].op.smgr = RelationGetSmgr(rel);
-		stream->ios[i].op.smgr_persistence = 0;
+		stream->ios[i].op.persistence = rel->rd_rel->relpersistence;
 		stream->ios[i].op.forknum = forknum;
 		stream->ios[i].op.strategy = strategy;
 	}

src/backend/storage/buffer/bufmgr.c

@@ -1104,7 +1104,7 @@ ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
 static pg_attribute_always_inline Buffer
 PinBufferForBlock(Relation rel,
 				  SMgrRelation smgr,
-				  char smgr_persistence,
+				  char persistence,
 				  ForkNumber forkNum,
 				  BlockNumber blockNum,
 				  BufferAccessStrategy strategy,
@@ -1113,14 +1113,13 @@ PinBufferForBlock(Relation rel,
 	BufferDesc *bufHdr;
 	IOContext	io_context;
 	IOObject	io_object;
-	char		persistence;
 
 	Assert(blockNum != P_NEW);
 
-	if (rel)
-		persistence = rel->rd_rel->relpersistence;
-	else
-		persistence = smgr_persistence;
+	/* Persistence should be set before */
+	Assert((persistence == RELPERSISTENCE_TEMP ||
+			persistence == RELPERSISTENCE_PERMANENT ||
+			persistence == RELPERSISTENCE_UNLOGGED));
 
 	if (persistence == RELPERSISTENCE_TEMP)
 	{
@@ -1195,6 +1194,7 @@ ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
 	ReadBuffersOperation operation;
 	Buffer		buffer;
 	int			flags;
+	char		persistence;
 
 	/*
 	 * Backward compatibility path, most code should use ExtendBufferedRel()
@@ -1216,12 +1216,17 @@ ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
 		return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
 	}
 
+	if (rel)
+		persistence = rel->rd_rel->relpersistence;
+	else
+		persistence = smgr_persistence;
+
 	if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
 				 mode == RBM_ZERO_AND_LOCK))
 	{
 		bool		found;
 
-		buffer = PinBufferForBlock(rel, smgr, smgr_persistence,
+		buffer = PinBufferForBlock(rel, smgr, persistence,
 								   forkNum, blockNum, strategy, &found);
 		ZeroAndLockBuffer(buffer, mode, found);
 		return buffer;
@@ -1233,7 +1238,7 @@ ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
 		flags = 0;
 	operation.smgr = smgr;
 	operation.rel = rel;
-	operation.smgr_persistence = smgr_persistence;
+	operation.persistence = persistence;
 	operation.forknum = forkNum;
 	operation.strategy = strategy;
 	if (StartReadBuffer(&operation,
@@ -1264,7 +1269,7 @@ StartReadBuffersImpl(ReadBuffersOperation *operation,
 
 		buffers[i] = PinBufferForBlock(operation->rel,
 									   operation->smgr,
-									   operation->smgr_persistence,
+									   operation->persistence,
 									   operation->forknum,
 									   blockNum + i,
 									   operation->strategy,
@@ -1410,10 +1415,8 @@ WaitReadBuffers(ReadBuffersOperation *operation)
 	buffers = &operation->buffers[0];
 	blocknum = operation->blocknum;
 	forknum = operation->forknum;
+	persistence = operation->persistence;
 
-	persistence = operation->rel
-		? operation->rel->rd_rel->relpersistence
-		: RELPERSISTENCE_PERMANENT;
 	if (persistence == RELPERSISTENCE_TEMP)
 	{
 		io_context = IOCONTEXT_NORMAL;

src/include/storage/bufmgr.h

@@ -117,7 +117,7 @@ struct ReadBuffersOperation
 	/* The following members should be set by the caller. */
 	Relation	rel;			/* optional */
 	struct SMgrRelationData *smgr;
-	char		smgr_persistence;	/* optional if rel != NULL */
+	char		persistence;
 	ForkNumber	forknum;
 	BufferAccessStrategy strategy;