jiayuasu commented on code in PR #3114:
URL: https://github.com/apache/sedona/pull/3114#discussion_r3609972006
##########
docs/api/sql/Raster-Operators/RS_AsRaster.md:
##########
@@ -26,7 +26,7 @@ Introduction: `RS_AsRaster` converts a vector geometry into a
raster dataset by
* `pixelType`: Defines data type of the output raster. This can be one of the
following, D (double), F (float), I (integer), S (short), US (unsigned short)
or B (byte).
* `allTouched` (Since: `v1.7.1`): Decides the pixel selection criteria. If set
to `true`, the function selects all pixels touched by the geometry, else,
selects only pixels whose centroids intersect the geometry. Defaults to `false`.
* `value`: The value to be used for assigning pixels covered by the geometry.
Defaults to using `1.0` if not provided.
-* `noDataValue`: Used for assigning the no data value of the resultant raster.
Defaults to `null` if not provided.
+* `noDataValue`: Used for assigning the no data value of the resultant raster;
pixels not covered by the geometry are set to this value. Defaults to `null` if
not provided, in which case uncovered pixels are `0` and the raster has no no
data value.
Review Comment:
One separate compatibility question: do we want omission to continue meaning
`null` here? I may be reading the PostGIS behavior too literally, but its
scalar overloads declare `nodataval DEFAULT 0`, and omission is observably
different from passing `NULL`.
This PostGIS query shows the distinction:
```sql
WITH g AS (
SELECT ST_GeomFromText(
'POLYGON ((0 0, 3 0, 3 3, 0 3, 0 0),
(1 1, 2 1, 2 2, 1 2, 1 1))'
) AS geom
),
r AS (
SELECT
ST_AsRaster(geom, 1.0, -1.0, '8BUI') AS omitted,
ST_AsRaster(
geom, 1.0, -1.0, '8BUI', 1.0, NULL::double precision
) AS explicit_null
FROM g
)
SELECT
ST_BandNoDataValue(omitted, 1),
ST_Value(omitted, 1, 2, 2, false),
ST_BandNoDataValue(explicit_null, 1),
ST_Value(explicit_null, 1, 2, 2, false)
FROM r;
```
I get `0 | 0 | NULL | 0`: both backgrounds contain zero, but only the
omitted case marks zero as nodata.
The comparable Sedona check is:
```sql
WITH inputs AS (
SELECT
ST_GeomFromWKT(
'POLYGON ((0 0, 3 0, 3 3, 0 3, 0 0),
(1 1, 2 1, 2 2, 1 2, 1 1))'
) AS geom,
RS_MakeEmptyRaster(
1, 'B', 3, 3, 0.0, 3.0, 1.0, -1.0, 0.0, 0.0, 0
) AS ref
),
r AS (
SELECT
RS_AsRaster(geom, ref, 'B') AS omitted,
RS_AsRaster(geom, ref, 'B', false, 1.0, 0.0) AS explicit_zero
FROM inputs
)
SELECT
RS_BandNoDataValue(omitted, 1),
RS_BandNoDataValue(explicit_zero, 1)
FROM r;
```
That gives `NULL | 0`. I can see a compatibility reason to preserve the
existing Sedona default, so this may be better handled separately. If matching
PostGIS defaults is the goal, though, the shorter overloads would need to pass
`0`, while explicit `NULL` could keep the current no-nodata behavior.
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