jiayuasu commented on code in PR #494:
URL: https://github.com/apache/parquet-format/pull/494#discussion_r2069349181
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Geospatial.md:
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@@ -94,6 +94,41 @@ Bounding box is defined as the thrift struct below in the
representation of
min/max value pair of coordinates from each axis. Note that X and Y Values are
always present. Z and M are omitted for 2D geospatial instances.
+Writers should follow the guidelines below when calculating bounding boxes in
+the presence of edge cases.
+
+* `null` instance: Skip it and continue processing the remaining
+ geospatial instances. Do not produce a bounding box if all instances are
null.
+* Non-`null` instance with [special geospatial
values](#special-geospatial-values):
+ * X and Y: Skip any special X or Y value and continue processing the
Review Comment:
Taking a LineString object as an example `LINESTRING (0 NaN, 0 1, 1 2)`:
We have 3 levels here:
1. A geospatial instance: this linestring object
2. A geospatial coordinate:
* we have 3 geospatial coordinates `0 NaN` , `0 1`, `1 2`
3. A geospatial value:
* For X, we have `0`, `0`, `1`
* For Y, we have `NaN`, `1`, `2`
The special geospatial value in this spec refers to the 3rd level. When
calculating bbox, we only omitted that single bad value `NaN`, and use X (`0`,
`0`, `1`) and Y (`1`, `2`).
That's why we didn't have a definition for `special coordinate` (2nd level)
because we look at the 3rd level directly
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