Filter

A filter step keeps the rows of a source layer that match a Boolean expression. The output is the same schema, the same geometry type, with fewer rows.

Use as a building block in any pipeline (filter, then buffer; filter, then group-by; filter, then spatial-join). Use alone when you want a permanently-filtered subset as its own item.

Inputs

• Source layer: any data layer, derived layer, or ArcGIS service sublayer.
• Expression: a Boolean SQL-style condition. See the expression syntax under Filters (map-editing).

Output

A new layer whose rows are those of the source for which the expression evaluates true. Schema is identical to the source.

How to use it on its own

1. New-item wizard → Derived layer.
2. Pick a Source.
3. Add a Filter step.
4. Type the expression.
5. Save.

Example

You have a fire-hydrant layer with thousands of features. You want a published layer of only the hydrants flagged as "needs-repair". One Filter step with expression status = 'needs-repair' produces it. Share the derived layer with the maintenance crew; they always see the current backlog.

Filter step vs. map filter

If the only consumer is one map, set the filter on the map's layer reference instead. A derived layer materializes its rows into its own table; a map filter is a query-time scoping clause. The derived layer is the right choice when you want the subset itself to be a shareable, named, citable item.

Notes

• Indexed fields filter fast. If a filter is permanent and the source layer has many features, ask an admin to add an index on the field.
• NULL handling: field is null and field is not null are explicit. field = NULL is always false, like SQL.