Ensure that flex_table_t::geom_column() refers to the first one

Now that there are multiple geometry columns allowed this makes sure we
always have the first one (which is important for clustering).

Remove the `column.set_not_null();` in `add_column()` for geometry
columns because it did not work anyway. It is overwritten by the
`column.set_not_null(...)` call right outside the `add_column()` call.

Author: joto

src/flex-table.cpp

@@ -73,15 +73,14 @@ flex_table_column_t &flex_table_t::add_column(std::string const &name,
            (m_columns.size() == 1 &&
             m_columns[0].type() == table_column_type::id_type));
 
-    m_columns.emplace_back(name, type, sql_type);
-    auto &column = m_columns.back();
+    auto &column = m_columns.emplace_back(name, type, sql_type);
 
     if (column.is_geometry_column()) {
-        if (m_geom_column != std::numeric_limits<std::size_t>::max()) {
+        if (m_geom_column == std::numeric_limits<std::size_t>::max()) {
+            m_geom_column = m_columns.size() - 1;
+        } else {
             m_has_multiple_geom_columns = true;
         }
-        m_geom_column = m_columns.size() - 1;
-        column.set_not_null();
     }
 
     return column;

src/flex-table.hpp

@@ -110,7 +110,7 @@ class flex_table_t
         return m_geom_column != std::numeric_limits<std::size_t>::max();
     }
 
-    // XXX should we allow several geometry columns?
+    /// Get the (first, if there are multiple) geometry column.
     flex_table_column_t const &geom_column() const noexcept
     {
         assert(has_geom_column());
@@ -218,7 +218,10 @@ class flex_table_t
      */
     std::vector<flex_table_column_t> m_columns;
 
-    /// Index of the geometry column in m_columns. Default means no geometry.
+    /**
+     * Index of the (first) geometry column in m_columns. Default means no
+     * geometry column.
+     */
     std::size_t m_geom_column = std::numeric_limits<std::size_t>::max();
 
     /**