New feature: ST_Segmentize

[umartin]

It would be nice to have something like https://postgis.net/docs/ST_Segmentize.html to break up large geometries for better partitioning and indexing.

Unfortunately I'm swamped so I won't have time work on this myself in the immediate future.

[jiayuasu]

Does this work for you? https://sedona.apache.org/latest/api/sql/Function/?h=st_sub#st_subdivideexplode

[umartin]

Since ST_SubDivideExplode splits on vertices it doesn't work on long lines with few vertices. If ST_SubDivideExplode is combined with ST_Segmentize it works better. ST_Segmentize introduces more vertices that ST_SubDivideExplode can split on.

But what I really want is something similar to subdivide but using length instead of max vertices. As described here in the example using a cross lateral join: https://postgis.net/docs/ST_LineSubstring.html

I was able to translate the query to sedona/spark but it's not pretty.

with line as (
    select col1 as id, col2 as sublen, ST_GeomFromWKT(col3) as geom
    from values (1, 50, 'LINESTRING (0 0, 99 99, 100 101)'), -- Length > sublen
                (2, 500, 'LINESTRING (0 0, 0 500)'), -- Length = sublen
                (3, 500, 'LINESTRING (0 0, 100 100)') -- Length < sublen
)
, line_seq as (
    select *, ST_Length(geom) as len, explode(sequence(0, floor(ST_Length(geom) / sublen))) as segment
    from line
)
select id, st_linesubstring(geom, segment * sublen / len, (segment +1) * sublen / len)
from line_seq
-- skip last segment if line length is exact multiple of sublen
where sublen * segment / len != 1.0

1,"LINESTRING (0 0, 35.35533905932738 35.35533905932738)"
1,"LINESTRING (35.35533905932738 35.35533905932738, 70.71067811865476 70.71067811865476)"
1,"LINESTRING (70.71067811865476 70.71067811865476, 99 99, 100 101)"
2,"LINESTRING (0 0, 0 500)"
3,"LINESTRING (0 0, 100 100)"