# geo_json

## Description

One GeoJSON FeatureCollection. Each SQL row becomes a Feature.
The output detects its native geometry column. Supported shapes are Point,
MultiPoint, LineString, MultiLineString, Polygon and MultiPolygon, using native
coordinate types. GeometryCollection is unsupported;
`geo_json_unsupported_geometry='null'` can replace it with NULL on input.

Input and output. Select it with `FORMAT geo_json`. Names ignore ASCII case; use the snake_case name shown here.

Output detects exactly one column containing a native geometry alias; there is no geometry-column setting. For an all-NULL geometry column, name it geometry. A column named id becomes the feature identifier; other columns become properties. A single object-valued column named properties can supply that object directly.

Input binds the fixed id, geometry and properties members. Coordinates must be finite. Geometry validation additionally checks line/ring sizes, ring closure and nonempty collections. GeometryCollection is not supported; the configured null policy can validate and replace it on input.

```text
SELECT expressions FORMAT geo_json;
INSERT INTO table [(columns)] [SETTINGS ...] FORMAT geo_json
<data>
```

## Example usage

```sql
SELECT CAST('[1,2]' AS Point) AS geometry, 'Ada' AS name FORMAT geo_json;
```

```text
{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":[1,2]},"properties":{"name":"Ada"}}]}
```

Output has no trailing newline.

### Detecting the geometry by its value type

The geometry column can have an application-specific name:

```sql
SELECT CAST('[1,2]' AS Point) AS location, 'Depot' AS name
FORMAT geo_json;
```

```text
{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":[1,2]},"properties":{"name":"Depot"}}]}
```

Output has no trailing newline.

## Format settings

Use a statement `SETTINGS` clause; these options are not persisted by `SET`.

| Setting                         | Type     | Default | Meaning                                                                                                                                   |
| ------------------------------- | -------- | ------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| `geo_json_unsupported_geometry` | `String` | `throw` | Reject unsupported geometry types on input; null validates them and stores NULL when geometry is requested.                               |
| `geo_json_validate_geometry`    | `Bool`   | `1`     | Validate line lengths, ring lengths and closure, and nonempty geometry containers on input and output; coordinates must always be finite. |
| `snappy_mode`                   | `String` | `basic` | Read Snappy client files as basic (Hadoop blocks) or framed (standard streaming format).                                                  |