bzr commit into connector-net-6.0 branch (vvaintroub:828) Bug#48243

[Vladislav Vaintroub]

#At file:///H:/connector_net/6.0/ based on revid:vvaintroub@stripped

  828 Vladislav Vaintroub	2010-07-28
      Bug #48243 : improve write performance of compressed stream.
      
      Reduce number of network writes in CompressAndSendCache() 
      from eight (a single write operation for  each  byte  in packet 
      length prefix plus single write for data itself) to one (send packet
      length prefix and data in a single buffer).
      
      This fixes was a regression from  5.2 (in 5.2, buffered output 
      was used, and writing bytes individually was not a problem)

    modified:
      CHANGES
      MySql.Data/Provider/Source/CompressedStream.cs
=== modified file 'CHANGES'
--- a/CHANGES	2010-07-27 21:53:37 +0000
+++ b/CHANGES	2010-07-28 14:05:00 +0000
@@ -1,4 +1,6 @@
-- Improve performance of MySqlHelper.EscapeString() (Bug#48243)
+- Improve performance of write operations (e.g insert) if compression is enabled
+  (Bug #48243)
+- Improve performance of MySqlHelper.EscapeString()
 - Fix membership provider creation failure, when default database character set is different from latin1 (Bug #53174)
 - Fix "Connection must be valid and open" exception When UpdateBatchSize > 1 
   and MySqlDataAdapter is not using an open connection (Bug #38411)

=== modified file 'MySql.Data/Provider/Source/CompressedStream.cs'
--- a/MySql.Data/Provider/Source/CompressedStream.cs	2009-07-29 11:06:15 +0000
+++ b/MySql.Data/Provider/Source/CompressedStream.cs	2010-07-28 14:05:00 +0000
@@ -209,35 +209,40 @@ namespace MySql.Data.MySqlClient
 
             // now we set our compressed and uncompressed lengths
             // based on if our compression is going to help or not
+            MemoryStream memStream;
+
             if (compressedBuffer == null)
             {
                 compressedLength = cache.Length;
                 uncompressedLength = 0;
+                memStream = cache;
             }
             else
             {
                 compressedLength = compressedBuffer.Length;
                 uncompressedLength = cache.Length;
+                memStream = compressedBuffer;
             }
 
-            baseStream.WriteByte((byte) (compressedLength & 0xff));
-            baseStream.WriteByte((byte) ((compressedLength >> 8) & 0xff));
-            baseStream.WriteByte((byte) ((compressedLength >> 16) & 0Xff));
-            baseStream.WriteByte(seq);
-            baseStream.WriteByte((byte) (uncompressedLength & 0xff));
-            baseStream.WriteByte((byte) ((uncompressedLength >> 8) & 0xff));
-            baseStream.WriteByte((byte) ((uncompressedLength >> 16) & 0Xff));
-
-            if (compressedBuffer == null)
-                baseStream.Write(cacheBuffer, 0, (int) cache.Length);
-            else
-            {
-                byte[] compressedBytes = compressedBuffer.GetBuffer();
-                baseStream.Write(compressedBytes, 0, (int) compressedBuffer.Length);
-            }
+            // Make space for length prefix (7 bytes) at the start of output
+            long dataLength = memStream.Length;
+            int bytesToWrite = (int)dataLength + 7;
+            memStream.SetLength(bytesToWrite);
+
+            byte[] buffer = memStream.GetBuffer();
+            Array.Copy(buffer, 0, buffer, 7, dataLength);
+
+            // Write length prefix
+            buffer[0] = (byte) (compressedLength & 0xff);
+            buffer[1] = (byte) ((compressedLength >> 8) & 0xff);
+            buffer[2] = (byte) ((compressedLength >> 16) & 0xff);
+            buffer[3] = seq;
+            buffer[4] = (byte) (uncompressedLength & 0xff);
+            buffer[5] = (byte) ((uncompressedLength >> 8) & 0xff);
+            buffer[6] = (byte) ((uncompressedLength >> 16) & 0xff);
 
+            baseStream.Write(buffer, 0, bytesToWrite);
             baseStream.Flush();
-
             cache.SetLength(0);
         }
 


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