Opened 14 years ago
Closed 14 years ago
#549 closed enhancement (fixed)
ST_isCollection
Reported by: | strk | Owned by: | strk |
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Priority: | medium | Milestone: | PostGIS 2.0.0 |
Component: | postgis | Version: | master |
Keywords: | Cc: |
Description
ST_isCollection(geometry)
A function returning TRUE if the argument geometry is of any COLLECTION type (MULTI*, GEOMETRYCOLLECTION).
This will be useful now that ST_NumGeometries returns 1 rather than NULL for non-collections.
Attachments (1)
Change History (15)
comment:1 by , 14 years ago
comment:2 by , 14 years ago
Without the typos :
+PG_FUNCTION_INFO_V1(LWGEOM_ST_IsCollection); +int ST_IsCollection(PG_FUNCTION_ARGS) +{ + PG_LWGEOM* geom; + geom = (PG_LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0)); + + return lwgeom_is_collection(geom->type); +}
I don't have a setup to test this from PostGIS svn right now, so I can't tell if it works or not though it compiles fine with this patch.
comment:4 by , 14 years ago
Something like this ?
There should also be a test on 'GEOMETRYCOLLECTION EMPTY' but I don't know what it should return. Is an empty geometry a collection ? Maybe could the C function be patched to catch that case.
$ svn diff Index: iscollection_expected =================================================================== --- iscollection_expected (revision 0) +++ iscollection_expected (revision 0) @@ -0,0 +1,11 @@ +f +f +f +t +t +t +t +t +t +t +t Index: iscollection.sql =================================================================== --- iscollection.sql (revision 0) +++ iscollection.sql (revision 0) @@ -0,0 +1,17 @@ +-- Ensure there are no false-positives +SELECT ST_IsCollection('POINT(42 42)'); +SELECT ST_IsCollection('POLYGON((0 0, 10 0, 10 10, 0 10, 0 0))'); +SELECT ST_IsCollection('LINESTRING(0 0, 10 10)'); + +--Ensure that all collections return true (even if they contain a single geometry). +SELECT ST_IsCollection('MULTIPOINT((0 0))'); +SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'); + +SELECT ST_IsCollection('MULTILINE((0 0, 10 10))'); +SELECT ST_IsCollection('MULTILINE((0 0, 10 10), (100 100, 142 142))'); + +SELECT ST_IsCollection('MULTIPOLYGON(((0 0, 10 0, 10 10, 10 0, 0 0)))'); +SELECT ST_IsCollection('MULTIPOLYGON(((0 0, 10 0, 10 10, 10 0, 0 0), (100 100, 110 100, 110 110, 100 110, 100 100)))'); + +SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'); +SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0), POINT(42 42))');
follow-up: 6 comment:5 by , 14 years ago
Is an empty geometry a collection ?
Well, a POINT EMPTY isn't, a GEOMETRYCOLLECTION EMPTY is, a MULTILINESTRING EMPTY is.
But this is my POV, not necessarely what you're looking for.
It was you proposing the function
Anyway, my suggestion should pretty much match the NULL result from ST_GetNumGeometries, which was the whole reason to suggest this new function, right ? It used to return 0 for GEOMETRYCOLLECTION EMPTY and NULL for POINT EMPTY.
comment:6 by , 14 years ago
Replying to strk:
Well, a POINT EMPTY isn't, a GEOMETRYCOLLECTION EMPTY is, a MULTILINESTRING EMPTY is. But this is my POV, not necessarely what you're looking for. It was you proposing the function
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Anyway, my suggestion should pretty much match the NULL result from ST_GetNumGeometries, which was the whole reason to suggest this new function, right ? It used to return 0 for GEOMETRYCOLLECTION EMPTY and NULL for POINT EMPTY.
That seems coherent. The C function should be ok. So here we go for the tests :
$ svn diff Index: iscollection_expected =================================================================== --- iscollection_expected (revision 0) +++ iscollection_expected (revision 0) @@ -0,0 +1,18 @@ +f +f +f +f +f +f +t +t +t +t +t +t +t +t +t +t +t +t Index: iscollection.sql =================================================================== --- iscollection.sql (revision 0) +++ iscollection.sql (revision 0) @@ -0,0 +1,27 @@ +-- Ensure there are no false-positives +SELECT ST_IsCollection('POINT(42 42)'); +SELECT ST_IsCollection('POLYGON((0 0, 10 0, 10 10, 0 10, 0 0))'); +SELECT ST_IsCollection('LINESTRING(0 0, 10 10)'); +SELECT ST_IsCollection('POINT EMPTY'); +SELECT ST_IsCollection('POLYGON EMPTY'); +SELECT ST_IsCollection('LINESTRING EMPTY'); + +--Ensure that all collections return true (even if they contain a single geometry). +SELECT ST_IsCollection('MULTIPOINT EMPTY'); +SELECT ST_IsCollection('MULTIPOINT((0 0))'); +SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'); + +SELECT ST_IsCollection('MULTILINESTRING EMPTY'); +SELECT ST_IsCollection('MULTILINESTRING((0 0, 10 10))'); +SELECT ST_IsCollection('MULTILINESTRING((0 0, 10 10), (100 100, 142 142))'); + +SELECT ST_IsCollection('MULTIPOLYGON EMPTY'); +SELECT ST_IsCollection('MULTIPOLYGON(((0 0, 10 0, 10 10, 0 10, 0 0)))'); +SELECT ST_IsCollection('MULTIPOLYGON(((0 0, 10 0, 10 10, 0 10, 0 0)), ((100 100, 110 100, 110 110, 100 110, 100 100)))'); + +SELECT ST_IsCollection('GEOMETRYCOLLECTION EMPTY'); +SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'); +SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0), POINT(42 42))'); +
comment:7 by , 14 years ago
Owner: | changed from | to
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Status: | new → assigned |
Your name for the ChangeLog ?
comment:8 by , 14 years ago
Oh, also the patch for postgis/postgis.sql.in.c is missing, and doc/reference_accessor.xml
follow-up: 11 comment:9 by , 14 years ago
I'm rewriting the code myself, and doing the sql part too. Note that postgis doesn't currently really support typed empty geometries, so I'll drop those tests from the regression
comment:10 by , 14 years ago
So, r5718 contains the code and tests. I took the chance to use sliced detoasting which would be nice to do for a few more functions too.
Documentation in reference_accessor.xml is still missing
comment:11 by , 14 years ago
Replying to strk:
I'm rewriting the code myself, and doing the sql part too.
Ok great.
Note that postgis doesn't currently really support typed empty geometries, so I'll drop those tests from the regression
That was what I thought but as we talked about them here I included them just in case.
This is quite a minor patch, like the ST_DumpPoints I did before, but however if you want to include me in the ChangeLog my name is Maxime van Noppen (maxime@…).
Great work, thanks!
comment:14 by , 14 years ago
Resolution: | → fixed |
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Status: | assigned → closed |
All done in r5723
It's been a pleasure
I don't know all the internals so this might be wrong but here's a first try :