commit 4b4e926fe8c805a7b3abcc8def4009177aa3210a
Author: Shoaib Lari <slari@pivotal.io>
Date:   Tue Jul 5 10:47:42 2016 -0700

    Fix error message for record length too long.
    
    Make the error message more descriptive when cannot enlarge buffer inside
    allocate_recordbuf().

diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index dcf747c..ae8a82e 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -25,7 +25,8 @@
 #include "common/pg_lzcompress.h"
 #include "replication/origin.h"
 
-static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
+static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength,
+							   uint32 *newSizeOut);
 
 static bool ValidXLogPageHeader(XLogReaderState *state, XLogRecPtr recptr,
 					XLogPageHeader hdr);
@@ -110,7 +111,7 @@ XLogReaderAllocate(XLogPageReadCB pagereadfunc, void *private_data)
 	 * Allocate an initial readRecordBuf of minimal size, which can later be
 	 * enlarged if necessary.
 	 */
-	if (!allocate_recordbuf(state, 0))
+	if (!allocate_recordbuf(state, 0, NULL))
 	{
 		pfree(state->errormsg_buf);
 		pfree(state->readBuf);
@@ -143,7 +144,8 @@ XLogReaderFree(XLogReaderState *state)
 
 /*
  * Allocate readRecordBuf to fit a record of at least the given length.
- * Returns true if successful, false if out of memory.
+ * Returns true if successful, false if out of memory.  If newSizeOut is
+ * non-NULL, it will be set to the size of the attempted allocation.
  *
  * readRecordBufSize is set to the new buffer size.
  *
@@ -153,13 +155,16 @@ XLogReaderFree(XLogReaderState *state)
  * abort records might need more space.)
  */
 static bool
-allocate_recordbuf(XLogReaderState *state, uint32 reclength)
+allocate_recordbuf(XLogReaderState *state, uint32 reclength, uint32 *newSizeOut)
 {
 	uint32		newSize = reclength;
 
 	newSize += XLOG_BLCKSZ - (newSize % XLOG_BLCKSZ);
 	newSize = Max(newSize, 5 * Max(BLCKSZ, XLOG_BLCKSZ));
 
+	if (newSizeOut)
+		*newSizeOut = newSize;
+
 	if (state->readRecordBuf)
 		pfree(state->readRecordBuf);
 	state->readRecordBuf =
@@ -201,6 +206,7 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
 	uint32		pageHeaderSize;
 	bool		gotheader;
 	int			readOff;
+	uint32 		newSizeOut;
 
 	/*
 	 * randAccess indicates whether to verify the previous-record pointer of
@@ -334,12 +340,12 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
 	 * Enlarge readRecordBuf as needed.
 	 */
 	if (total_len > state->readRecordBufSize &&
-		!allocate_recordbuf(state, total_len))
+		!allocate_recordbuf(state, total_len, &newSizeOut))
 	{
-		/* We treat this as a "bogus data" condition */
-		report_invalid_record(state, "record length %u at %X/%X too long",
-							  total_len,
-							  (uint32) (RecPtr >> 32), (uint32) RecPtr);
+		report_invalid_record(state,
+							  "cannot allocate %u bytes for record length %u at %X/%X",
+							  newSizeOut, total_len, (uint32) (RecPtr >> 32),
+							  (uint32) RecPtr);
 		goto err;
 	}