MXS-2213: Clear stored PS information

The information stored for each prepared statement would not be cleared
until the end of the session. This is a problem if the sessions last for a
very long time as the stored information is unused once a COM_STMT_CLOSE
has been received.

In addition to this, the session command response maps were not cleared
correctly if all backends had processed all session commands.

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -202,6 +202,13 @@ bool route_single_stmt(RWSplit *inst, RWSplitSession *rses, GWBUF *querybuf, con
 
     if (not_locked_to_master && is_ps_command(command))
     {
+        if (command == MXS_COM_STMT_CLOSE)
+        {
+            // Remove the command from the PS mapping
+            rses->ps_manager.erase(stmt_id);
+            rses->ps_handles.erase(mxs_mysql_extract_ps_id(querybuf));
+        }
+
         /** Replace the client statement ID with our internal one only if the
          * target node is not the current master */
         replace_binary_ps_id(querybuf, stmt_id);
@@ -422,6 +429,11 @@ bool route_session_write(RWSplitSession *rses, GWBUF *querybuf,
         {
             rses->sescmd_responses.erase(rses->sescmd_responses.begin(), it);
         }
+        else
+        {
+            // All responses processed
+            rses->sescmd_responses.clear();
+        }
     }
     else
     {

server/modules/routing/readwritesplit/rwsplitsession.cc

@@ -86,6 +86,10 @@ bool RWBackend::write(GWBUF* buffer, response_type type)
                 // Any non-zero flag value means that we have an open cursor
                 m_opening_cursor = flags != 0;
             }
+            else if (cmd == MXS_COM_STMT_CLOSE)
+            {
+                m_ps_handles.erase(it);
+            }
             else if (cmd == MXS_COM_STMT_FETCH)
             {
                 // Number of rows to fetch is a 4 byte integer after the ID