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Posted to issues@sedona.apache.org by "paleolimbot (via GitHub)" <gi...@apache.org> on 2026/05/06 22:10:39 UTC
[I] c/sedona-s2geography: Reduce precision may have differing behaviour when some components collapse in a geography [sedona-db]
paleolimbot opened a new issue, #822:
URL: https://github.com/apache/sedona-db/issues/822
I removed a test so that I can investigate properly from https://github.com/apache/sedona-db/pull/816 for ST_ReducePrecision for geography (which bigquery calls ST_SnapToGrid). We might also want to investigate naming them the same thing (but also investigate the specifics of the difference between ST_SnapToGrid and ST_ReducePrecision in PostGIS...I think snaptogrid is faster but maybe doesn't do validity checking in the same way).
```python
# Linestring: component collapses because the endpoints snap together
pytest.param(
"LINESTRING (0.01 0.02, 0.03 0.04)",
1.0,
"LINESTRING EMPTY",
id="linestring_collapse",
),
```
BigQuery gives `POINT (0 0)` here, which keep the collapsed component
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Re: [I] c/sedona-s2geography: Reduce precision may have differing behaviour when some components collapse in a geography [sedona-db]
Posted by "paleolimbot (via GitHub)" <gi...@apache.org>.
paleolimbot commented on issue #822:
URL: https://github.com/apache/sedona-db/issues/822#issuecomment-4393776945
For ST_Simplify, ZM behaviour when simplification occurs may not be correct:
```python
# Linestring with Z: large tolerance removes intermediate vertex
pytest.param(
"LINESTRING Z (0 0 100, 5 1 150, 10 0 200)",
200000.0,
"LINESTRING Z (0 0 100, 10 0 200)",
id="linestring_z_simplify",
),
# Linestring with M: large tolerance removes intermediate vertex
pytest.param(
"LINESTRING M (0 0 100, 5 1 150, 10 0 200)",
200000.0,
"LINESTRING M (0 0 100, 10 0 200)",
id="linestring_m_simplify",
),
# Linestring with ZM: large tolerance removes intermediate vertex
pytest.param(
"LINESTRING ZM (0 0 100 1000, 5 1 150 1500, 10 0 200 2000)",
200000.0,
"LINESTRING ZM (0 0 100 1000, 10 0 200 2000)",
id="linestring_zm_simplify",
),
```
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Re: [I] c/sedona-s2geography: Reduce precision may have differing behaviour when some components collapse in a geography [sedona-db]
Posted by "paleolimbot (via GitHub)" <gi...@apache.org>.
paleolimbot commented on issue #822:
URL: https://github.com/apache/sedona-db/issues/822#issuecomment-4393762285
Also in ST_Simplify:
```python
# Linestring: collapse when endpoints merge
pytest.param(
"LINESTRING (0 0, 0.0001 0.0001)",
1000000.0,
"LINESTRING EMPTY",
id="linestring_collapse",
),
```
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