set_filter_expr

Sets a filter among the rows presented by this.

The filter is defined by a filter expression which can be any SQL valid expression using this's columns. For instance if this has the "id" and "name" columns, then a filter can be "length(name) < 5" to filter only the rows where the length of the name is strictly inferior to 5, or "id >= 1000 and id < 2000 order by name limit 50" to filter only the rows where the id is between 1000 and 2000, ordered by name and limited to 50 rows.

Note about column names: real column names can be used (double quoted if necessary), but columns can also be named "_<column number>" with column numbers starting at 1.

Note that any previous filter expression is replaced with the new filter_expr if no error occurs (if an error occurs, then any previous filter is left unchanged).

Parameters:

this	a DataProxy object
filter_expr	an SQL based expression which will filter the contents of this, or null to remove any previous filter

Returns:

TRUE if no error occurred