Merge branch '2.2' into 2.3

Documentation/Routers/ReadWriteSplit.md

@@ -76,9 +76,28 @@ taken into use by new sessions.
 ### `max_slave_connections`
 
 **`max_slave_connections`** sets the maximum number of slaves a router session
-uses at any moment. The default is to use all available slaves.
+uses at any moment. The default is to use at most 255 slave connections per
+client connection. In older versions the default was to use all available slaves
+with no limit.
 
-	max_slave_connections=<max. number, or % of available slaves>
+```
+max_slave_connections=<max. number, or % of available slaves>
+```
+
+For example, if you have configured MaxScale with one master and three slaves
+and set `max_slave_connections=2`, for each client connection a connection to
+the master and two slave connections would be opened. The read query load
+balancing is then done between these two slaves and writes are sent to the
+master.
+
+By tuning this parameter, you can control how dynamic the load balancing is at
+the cost of extra created connections. With a lower value of
+`max_slave_connections`, less connections per session are created and the set of
+possible slave servers is smaller. With a higher value in
+`max_slave_connections`, more connections are created which requires more
+resources but load balancing will almost always give the best single query
+response time and performance. Longer sessions are less affected by a high
+`max_slave_connections` as the relative cost of opening a connection is lower.
 
 ### `max_slave_replication_lag`
 

query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc

@@ -829,6 +829,7 @@ static uint32_t resolve_query_type(parsing_info_t* pi, THD* thd)
     }
     else if (lex->option_type == OPT_SESSION)
     {
+        bool do_return = true;
         /**
          * SHOW syntax http://dev.mysql.com/doc/refman/5.6/en/show.html
          */
@@ -872,10 +873,16 @@ static uint32_t resolve_query_type(parsing_info_t* pi, THD* thd)
         }
         else
         {
-            type |= QUERY_TYPE_READ;
+            // This will cause the type of a statement like
+            // "SET STATEMENT ... FOR XYZ" to be the type
+            // of XYZ.
+            do_return = false;
         }
 
-        goto return_qtype;
+        if (do_return)
+        {
+            goto return_qtype;
+        }
     }
 
     /**

query_classifier/test/maxscale.test

@@ -112,3 +112,6 @@ SET STATEMENT max_statement_time=30 FOR SELECT seq FROM seq_0_to_100000;
 
 # MXS-1935
 PREPARE a FROM @sql;
+
+# MXS-2207
+SET STATEMENT max_statement_time=30 FOR UPDATE tbl SET a = 42;