Add BufFileRead variants with short read and EOF detection

Most callers of BufFileRead() want to check whether they read the full
specified length.  Checking this at every call site is very tedious.
This patch provides additional variants BufFileReadExact() and
BufFileReadMaybeEOF() that include the length checks.

I considered changing BufFileRead() itself, but this function is also
used in extensions, and so changing the behavior like this would
create a lot of problems there.  The new names are analogous to the
existing LogicalTapeReadExact().

Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/f3501945-c591-8cc3-5ef0-b72a2e0eaa9c@enterprisedb.com

1 files changed, 4 insertions, 28 deletions

diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index f3856c9843..d8b8a374c6 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -2069,19 +2069,13 @@ apply_spooled_messages(FileSet *stream_fileset, TransactionId xid,
 		CHECK_FOR_INTERRUPTS();
 
 		/* read length of the on-disk record */
-		nbytes = BufFileRead(stream_fd, &len, sizeof(len));
+		nbytes = BufFileReadMaybeEOF(stream_fd, &len, sizeof(len), true);
 
 		/* have we reached end of the file? */
 		if (nbytes == 0)
 			break;
 
 		/* do we have a correct length? */
-		if (nbytes != sizeof(len))
-			ereport(ERROR,
-					(errcode_for_file_access(),
-					 errmsg("could not read from streaming transaction's changes file \"%s\": read only %zu of %zu bytes",
-							path, nbytes, sizeof(len))));
-
 		if (len <= 0)
 			elog(ERROR, "incorrect length %d in streaming transaction's changes file \"%s\"",
 				 len, path);
@@ -2090,12 +2084,7 @@ apply_spooled_messages(FileSet *stream_fileset, TransactionId xid,
 		buffer = repalloc(buffer, len);
 
 		/* and finally read the data into the buffer */
-		nbytes = BufFileRead(stream_fd, buffer, len);
-		if (nbytes != len)
-			ereport(ERROR,
-					(errcode_for_file_access(),
-					 errmsg("could not read from streaming transaction's changes file \"%s\": read only %zu of %zu bytes",
-							path, nbytes, (size_t) len)));
+		BufFileReadExact(stream_fd, buffer, len);
 
 		BufFileTell(stream_fd, &fileno, &offset);
 
@@ -3993,7 +3982,6 @@ static void
 subxact_info_read(Oid subid, TransactionId xid)
 {
 	char		path[MAXPGPATH];
-	size_t		nread;
 	Size		len;
 	BufFile    *fd;
 	MemoryContext oldctx;
@@ -4013,12 +4001,7 @@ subxact_info_read(Oid subid, TransactionId xid)
 		return;
 
 	/* read number of subxact items */
-	nread = BufFileRead(fd, &subxact_data.nsubxacts, sizeof(subxact_data.nsubxacts));
-	if (nread != sizeof(subxact_data.nsubxacts))
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not read from streaming transaction's subxact file \"%s\": read only %zu of %zu bytes",
-						path, nread, sizeof(subxact_data.nsubxacts))));
+	BufFileReadExact(fd, &subxact_data.nsubxacts, sizeof(subxact_data.nsubxacts));
 
 	len = sizeof(SubXactInfo) * subxact_data.nsubxacts;
 
@@ -4037,14 +4020,7 @@ subxact_info_read(Oid subid, TransactionId xid)
 	MemoryContextSwitchTo(oldctx);
 
 	if (len > 0)
-	{
-		nread = BufFileRead(fd, subxact_data.subxacts, len);
-		if (nread != len)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not read from streaming transaction's subxact file \"%s\": read only %zu of %zu bytes",
-						path, nread, len)));
-	}
+		BufFileReadExact(fd, subxact_data.subxacts, len);
 
 	BufFileClose(fd);
 }