Filter property

Applies to
TQDB, TQDBItem, TQDBView

Declaration
property Filter : TKey;

Description
The Filter property effectively screens certain keys from the index. If Filter is null (i.e. '') navigation operations can access every key in the index but, if not, only keys which match the Filter pattern are accessible.

The algorithm for pattern-matching is governed by the setting of UseGrepMatch.

N.B.: Be aware that filtered navigation carries a much greater overhead than unfiltered, e.g., with 10 character keys and the simple matching protocol:

   filter type      relative time
   none         20
   match every key   80
   match 1 in 10      240
   match 1 in 100      1600
   match 1 in 1000      18000

The overhead is even greater for grep-style matching.

Setting ItemIndex directly is not affected by the Filter, nor are the search methods.