Expressions and Saved Schema

If the RDBMS cursor dataset overlay contains an expression column (or the original schema has been modified) new columns added to the underlying spatial tables are not displayed in Cadcorp SIS Desktop.

To display the new column in the schema the ‘Reset All’ button must be used (Overlays dialog box under the Schema tab). Note that the current overlay schema will be overwritten, so the expression column will be lost. Therefore make a copy of any expressions you want to keep.

Expression Caching

Expresssion result cache is a preference that can be switched on for RDBMS Cursor-based Datasets created in dynamic mode.

In situations where the result of an expression is static, Cadcorp SIS Desktop will remember the value rather than calculate it every time the user pans the map window or takes any action that causes Cadcorp SIS Desktop to redraw the overlay. If Expression result cache is switched off Cadcorp SIS Desktop will recalculate the values every time the map has to redraw.

Expression result cache can be switched on and off from File > Options:

Select the Miscellaneous tab from the left hand side of the dialog.

Check the Cursor-based Datasets tickbox under the Expression result cache folder.

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