Updates to dbshard router:

Added a parsing function to query classifier that returns an array of database names the query uses.
Added a check if the query targets a sharded database. If so, a hint is added that routes the query to the named server.

query_classifier/query_classifier.cc

@@ -1438,3 +1438,50 @@ char* skygw_get_qtype_str(
 	}
 	return qtype_str;
 }
+
+/**
+ * Returns an array of strings of databases that this query uses.
+ * If the database isn't defined in the query, it is assumed that this query only targets the current database.
+ * The value of @p size is set to the number of allocated strings. The caller is responsible for freeing all the allocated memory.
+ * @param querybuf GWBUF containing the query
+ * @param size Size of the resulting array
+ * @return A new array of strings containing the database names or NULL if no databases were found.
+ */
+char**		skygw_get_database_names(GWBUF* querybuf,int* size)
+{
+	LEX*			lex;
+	TABLE_LIST*		tbl;
+	char			**databases = NULL, **tmp = NULL;
+	int				currsz = 0,i = 0;
+
+  if( (lex = get_lex(querybuf)) == NULL)
+	{
+      goto retblock;
+    }        
+
+	lex->current_select = lex->all_selects_list;
+
+
+  while(lex->current_select){
+	  tbl = lex->current_select->join_list->head();
+	while(tbl)
+		{
+			if(strcmp(tbl->db,"skygw_virtual") != 0){
+				if(i>= currsz){
+					tmp = (char**)realloc(databases,sizeof(char*)*(currsz*2 + 1));
+					if(tmp == NULL) goto retblock;
+					databases = tmp;
+					currsz = currsz*2 + 1;
+				}				
+				databases[i++] = strdup(tbl->db);
+			}
+			tbl=tbl->next_local;
+		}
+	  
+    lex->current_select = lex->current_select->next_select_in_list();
+  }
+
+	retblock:
+	*size = i;
+	return databases;
+}

query_classifier/query_classifier.h

@@ -89,6 +89,7 @@ bool		is_drop_table_query(GWBUF* querybuf);
 bool		skygw_is_real_query(GWBUF* querybuf);
 void*		skygw_get_affected_tables(void* lexptr);
 char**		skygw_get_table_names(GWBUF* querybuf,int* tblsize,bool fullnames);
+char**		skygw_get_database_names(GWBUF* querybuf,int* size);
 char*           skygw_get_canonical(GWBUF* querybuf);
 bool            parse_query (GWBUF* querybuf);
 parsing_info_t* parsing_info_init(void (*donefun)(void *));