[CONJS-278] multiple part query (query bigger than 16M) wrongly reuse…

… send buffer #274

When sending query with size bigger than 16M, buffer send in socket might sometime be reused. Node.js doesn't permit reusing of socket buffer. Query send is then wrong.

lib/io/packet-output-stream.js

@@ -668,6 +668,7 @@ class PacketOutputStream {
         //if last packet fill the max size, must send an empty com to indicate that command end.
         this.writeEmptyPacket();
       }
+      this.buf = this.createBufferWithMinSize(remainingLen);
       this.pos = 4;
     }
   }
@@ -700,9 +701,24 @@ class PacketOutputStream {
       //if last packet fill the max size, must send an empty com to indicate that command end.
       this.writeEmptyPacket();
     }
+    this.buf = this.createBufferWithMinSize(remainingLen);
     this.pos = 4;
   }
 
+  createBufferWithMinSize(remainingLen) {
+    let newCapacity;
+    if (remainingLen + this.pos < MEDIUM_BUFFER_SIZE) {
+      newCapacity = MEDIUM_BUFFER_SIZE;
+    } else if (remainingLen + this.pos < LARGE_BUFFER_SIZE) {
+      newCapacity = LARGE_BUFFER_SIZE;
+    } else if (remainingLen + this.pos < BIG_BUFFER_SIZE) {
+      newCapacity = BIG_BUFFER_SIZE;
+    } else {
+      newCapacity = MAX_BUFFER_SIZE;
+    }
+    return Buffer.allocUnsafe(newCapacity);
+  }
+
   fastFlushDebug(cmd, packet) {
     this.stream.writeBuf(packet, cmd);
     this.stream.flush(true, cmd);