MXS-1624 Make the QC info object explicit

The query classifier stores information about the statement carried
by a GWBUF in the GWBUF itself. We need to be able to store that
object out side the lifetime of the GWBUF. So, we require that a
query classifier is capable of duplicating references to that object.

include/maxscale/query_classifier.h

@@ -17,7 +17,7 @@
 
 MXS_BEGIN_DECLS
 
-#define MXS_QUERY_CLASSIFIER_VERSION {2, 0, 0}
+#define MXS_QUERY_CLASSIFIER_VERSION {3, 0, 0}
 
 /**
  * qc_init_kind_t specifies what kind of initialization should be performed.
@@ -155,6 +155,14 @@ typedef enum qc_result
     QC_RESULT_ERROR
 } qc_result_t;
 
+/**
+ * QC_STMT_INFO is an opaque type where the query classifier stores
+ * information about a statement.
+ */
+typedef struct qc_stmt_info
+{
+} QC_STMT_INFO;
+
 /**
  * QUERY_CLASSIFIER defines the object a query classifier plugin must
  * implement and return.
@@ -406,6 +414,16 @@ typedef struct query_classifier
      * @return QC_RESULT_OK if @sql_mode is valid, otherwise QC_RESULT_ERROR.
      */
     int32_t (*qc_set_sql_mode)(qc_sql_mode_t sql_mode);
+
+    /**
+     * Dups the provided info object. After having been dupped, the info object
+     * can be stored on another GWBUF.
+     *
+     * @param info  The info to be dupped.
+     *
+     * @return The same info that was provided as argument.
+     */
+    QC_STMT_INFO* (*qc_dup)(QC_STMT_INFO* info);
 } QUERY_CLASSIFIER;
 
 /**

query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc

@@ -3488,6 +3488,13 @@ int32_t qc_mysql_set_sql_mode(qc_sql_mode_t sql_mode)
     return rv;
 }
 
+QC_STMT_INFO* qc_mysql_dup(QC_STMT_INFO* info)
+{
+    // TODO: Not implemented yet.
+    ss_dassert(!true);
+    return info;
+}
+
 /**
  * EXPORTS
  */
@@ -3521,6 +3528,7 @@ extern "C"
             qc_mysql_get_server_version,
             qc_mysql_get_sql_mode,
             qc_mysql_set_sql_mode,
+            qc_mysql_dup,
         };
 
         static MXS_MODULE info =

query_classifier/qc_sqlite/qc_sqlite.cc

@@ -4300,6 +4300,7 @@ static void qc_sqlite_set_server_version(uint64_t version);
 static void qc_sqlite_get_server_version(uint64_t* version);
 static int32_t qc_sqlite_get_sql_mode(qc_sql_mode_t* sql_mode);
 static int32_t qc_sqlite_set_sql_mode(qc_sql_mode_t sql_mode);
+static QC_STMT_INFO* qc_sqlite_dup(QC_STMT_INFO* info);
 
 static bool get_key_and_value(char* arg, const char** pkey, const char** pvalue)
 {
@@ -4958,6 +4959,13 @@ int32_t qc_sqlite_set_sql_mode(qc_sql_mode_t sql_mode)
     return rv;
 }
 
+QC_STMT_INFO* qc_sqlite_dup(QC_STMT_INFO* info)
+{
+    // TODO: Not implemented yet.
+    ss_dassert(!true);
+    return info;
+}
+
 /**
  * EXPORTS
  */
@@ -4991,6 +4999,7 @@ MXS_MODULE* MXS_CREATE_MODULE()
         qc_sqlite_get_server_version,
         qc_sqlite_get_sql_mode,
         qc_sqlite_set_sql_mode,
+        qc_sqlite_dup
     };
 
     static MXS_MODULE info =