Fix LZ4 tests for remaining buffer space.

We should flush the buffer when the remaining space is less than
the maximum amount that we might need, not when it is less than or
equal to the maximum amount we might need.

Jeevan Ladhe, per an observation from me.

Discussion: http://postgr.es/m/CANm22CgVMa85O1akgs+DOPE8NSrT1zbz5_vYfS83_r+6nCivLQ@mail.gmail.com

src/backend/replication/basebackup_lz4.c

@@ -193,7 +193,7 @@ bbsink_lz4_archive_contents(bbsink *sink, size_t avail_in)
 	 * LZ4F_compressBound(), ask the next sink to process the data so that we
 	 * can empty the buffer.
 	 */
-	if ((mysink->base.bbs_next->bbs_buffer_length - mysink->bytes_written) <=
+	if ((mysink->base.bbs_next->bbs_buffer_length - mysink->bytes_written) <
 		avail_in_bound)
 	{
 		bbsink_archive_contents(sink->bbs_next, mysink->bytes_written);
@@ -238,7 +238,7 @@ bbsink_lz4_end_archive(bbsink *sink)
 
 	Assert(mysink->base.bbs_next->bbs_buffer_length >= lz4_footer_bound);
 
-	if ((mysink->base.bbs_next->bbs_buffer_length - mysink->bytes_written) <=
+	if ((mysink->base.bbs_next->bbs_buffer_length - mysink->bytes_written) <
 		lz4_footer_bound)
 	{
 		bbsink_archive_contents(sink->bbs_next, mysink->bytes_written);

src/bin/pg_basebackup/bbstreamer_lz4.c

@@ -99,7 +99,7 @@ bbstreamer_lz4_compressor_new(bbstreamer *next, int compresslevel)
 	compressed_bound = LZ4F_compressBound(streamer->base.bbs_buffer.maxlen, prefs);
 
 	/* Enlarge buffer if it falls short of compression bound. */
-	if (streamer->base.bbs_buffer.maxlen <= compressed_bound)
+	if (streamer->base.bbs_buffer.maxlen < compressed_bound)
 		enlargeStringInfo(&streamer->base.bbs_buffer, compressed_bound);
 
 	ctxError = LZ4F_createCompressionContext(&streamer->cctx, LZ4F_VERSION);
@@ -170,7 +170,7 @@ bbstreamer_lz4_compressor_content(bbstreamer *streamer,
 	 */
 	out_bound = LZ4F_compressBound(len, &mystreamer->prefs);
 	Assert(mystreamer->base.bbs_buffer.maxlen >= out_bound);
-	if (avail_out <= out_bound)
+	if (avail_out < out_bound)
 	{
 			bbstreamer_content(mystreamer->base.bbs_next, member,
 							   mystreamer->base.bbs_buffer.data,
@@ -218,7 +218,7 @@ bbstreamer_lz4_compressor_finalize(bbstreamer *streamer)
 	/* Find out the footer bound and update the output buffer. */
 	footer_bound = LZ4F_compressBound(0, &mystreamer->prefs);
 	Assert(mystreamer->base.bbs_buffer.maxlen >= footer_bound);
-	if ((mystreamer->base.bbs_buffer.maxlen - mystreamer->bytes_written) <=
+	if ((mystreamer->base.bbs_buffer.maxlen - mystreamer->bytes_written) <
 		footer_bound)
 	{
 			bbstreamer_content(mystreamer->base.bbs_next, NULL,