MXS-2441: Extend maxsql extraction functions

Having helper methods that combine the index position search and value
extraction make it easier to deal with results that have a lot of fields
e.g. the output of SHOW SLAVE STATUS.

maxutils/maxsql/include/maxsql/mariadb.hh

@@ -115,6 +115,7 @@ public:
      * @return Value as string
      */
     std::string get_string(int64_t column_ind) const;
+    std::string get_string(const std::string& name) const;
 
     /**
      * Read an integer value from the current row and given column.
@@ -123,6 +124,7 @@ public:
      * @return Value as integer. If the data could not be parsed an error flag is set.
      */
     int64_t get_int(int64_t column_ind) const;
+    int64_t get_int(const std::string& name) const;
 
     /**
      * Check if field is null.
@@ -140,6 +142,7 @@ public:
      * @return Value as boolean. Returns true if the field contains '1'.
      */
     bool get_bool(int64_t column_ind) const;
+    bool get_bool(const std::string& name) const;
 
     /**
      * Has a parsing error occurred during current row?

maxutils/maxsql/src/mariadb.cc

@@ -155,11 +155,35 @@ string QueryResult::get_string(int64_t column_ind) const
     return data ? data : "";
 }
 
+string QueryResult::get_string(const std::string& name) const
+{
+    auto idx = get_col_index(name);
+
+    if (idx != -1)
+    {
+        return get_string(idx);
+    }
+
+    return "";
+}
+
 int64_t QueryResult::get_int(int64_t column_ind) const
 {
     return parse_integer(column_ind, "integer");
 }
 
+int64_t QueryResult::get_int(const std::string& name) const
+{
+    auto idx = get_col_index(name);
+
+    if (idx != -1)
+    {
+        return get_int(idx);
+    }
+
+    return 0;
+}
+
 /**
  * Parse a 64bit integer. On parse error an error flag is set.
  *
@@ -212,6 +236,18 @@ bool QueryResult::get_bool(int64_t column_ind) const
     return rval;
 }
 
+bool QueryResult::get_bool(const std::string& name) const
+{
+    auto idx = get_col_index(name);
+
+    if (idx != -1)
+    {
+        return get_bool(idx);
+    }
+
+    return 0;
+}
+
 bool QueryResult::field_is_null(int64_t column_ind) const
 {
     mxb_assert(column_ind < get_col_count() && column_ind >= 0 && m_rowdata);