Merge pull request #1766 from michael-berlin/worker_pack_count_revert

vtworker: Revert --destination_pack_count to 10.

Author: michael-berlin

go/vt/worker/defaults.go

@@ -8,10 +8,13 @@ import "github.com/youtube/vitess/go/vt/throttler"
 
 const (
 	defaultSourceReaderCount = 10
-	// defaultDestinationPackCount is the number of rows which will be aggreated
-	// into one transaction. Note that higher values will increase memory
-	// consumption in vtworker, vttablet and mysql.
-	defaultDestinationPackCount    = 1000
+	// defaultDestinationPackCount is the number of StreamExecute responses which
+	// will be aggreated into one transaction. See the vttablet flag
+	// "-queryserver-config-stream-buffer-size" for the size (in bytes) of a
+	// StreamExecute response. As of 06/2015, the default for it was 32 kB.
+	// Note that higher values for this flag --destination_pack_count will
+	// increase memory consumption in vtworker, vttablet and mysql.
+	defaultDestinationPackCount    = 10
 	defaultMinTableSizeForSplit    = 1024 * 1024
 	defaultDestinationWriterCount  = 20
 	defaultMinHealthyRdonlyTablets = 2