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EmptyDataSet

procedure EmptyDataSet

Example​

procedure ScriptEvent(var Value: variant);
begin
  DATA1.EmptyDataSet;
  Value := DATA1.BOF and DATA1.EOF;
end;

Usage​

EmptyDataSet resets all records and local change state in the active client dataset without row-by-row deletion.

Usage notes

Treat it as irreversible disposal of the local packet unless a separate source can reload it. Do not use when row-level delete validation, auditing or database deletion is required.

Errors and side effects

Inactive state, inability to post or validate a pending edit, reset or resynchronisation failure, and dataset events can raise errors. The method does not disable controls, so use DeleteAll when controls should be suppressed during deletion.

Additional Technical Info​

EmptyDataSet is the inherited TCustomClientDataSet bulk reset explicitly re-exposed on TvxClientDataSet. It removes all local records without invoking Delete for each row.

The example is destructive, source-reviewed and was not executed by the documentation workflow. DeleteAll wraps this same method with controls disabled and is normally clearer Velox intent.

Signature and implementation

The method calls CheckBrowseMode, so an outstanding insert/edit can be posted before the reset. It resets the internal DSBase, marks its data-changed property true, marks provider EOF, resynchronises the cursor and initialises the active buffer.

It does not execute the ordinary BeforeDelete/AfterDelete lifecycle for every record. Bookmarks, row positions and current field values become invalid/empty. Schema field objects generally remain because this resets data rather than closing/recreating the dataset.

Change log and external persistence

The reset removes the current record store and its prior pending change history. This is not equivalent to producing one delete delta per original row. Normal Velox non-edit datasets have LogChanges disabled in any event.

No provider ApplyUpdates, SQL DELETE or transaction commit is performed here. An external database remains unchanged unless the owning workflow performs a separate supported persistence operation.

Performance and concurrency

This native bulk reset avoids script-level per-record navigation/delete overhead. It still mutates complete shared dataset state and is unsynchronised.

External references

Created 2026-07-15