Given two shapes A and B, the predicate function ST_Contains(A, B) returns true if:
- No point in B lies outside of shape A, and
- At least one point in the interior of B lies in the interior of A.
In other words, the exterior of shape A must not include any point in B, and one or more points of B's interior must lie in the interior of A.
This behavior is similar to ST_Covers, except that the criteria are more exacting, and therefore some pairs of shapes will be rejected by this function that would be accepted by ST_Covers.
ST_Contains works on the following data types:
ST_Contains will attempt to use any available spatial index to speed up its operation. Use the prefixed variant _ST_Contains if you do not want any spatial indexes to be used.
This function is the inverse of ST_Within.
Examples
The screenshots in these examples were generated using geojson.io, but they are designed to showcase the shapes, not the map. Representing GEOMETRY data in GeoJSON can lead to unexpected results if using geometries with SRIDs other than 4326 (as shown below).
True
In this example, ST_Contains returns true because:
- No point in the LineString B lies outside of the Polygon A, and
- At least one point in the interior of B lies in the interior of A.
SELECT ST_Contains(st_geomfromtext('SRID=4326;POLYGON((-87.906471 43.038902, -95.992775 36.153980, -75.704722 36.076944, -87.906471 43.038902))'), st_geomfromtext('SRID=4326;LINESTRING(-88.243385 40.116421, -87.906471 43.038902, -95.992775 36.153980)'));
st_contains
---------------
true
(1 row)
False
In this example, ST_Contains returns false because:
- At least one point in the interior of LineString B does not lie in the interior of the Polygon A.
Note that A query against these shapes with ST_Covers will return true.
SELECT st_contains(st_geomfromtext('SRID=4326;POLYGON((-87.906471 43.038902, -95.992775 36.153980, -75.704722 36.076944, -87.906471 43.038902))'), st_geomfromtext('SRID=4326;LINESTRING( -87.906471 43.038902, -95.992775 36.153980)'));
st_contains
---------------
false
(1 row)
See also
- Working with Spatial Data
- Spatial and GIS Glossary of Terms
- Spatial indexes
- Spatial functions
ST_CoversST_CoveredByST_WithinST_IntersectsST_CoveredByST_CoversST_DisjointST_EqualsST_OverlapsST_TouchesST_ConvexHullST_Union- Migrate from Shapefiles
- Migrate from GeoJSON
- Migrate from GeoPackage
- Migrate from OpenStreetMap
- Introducing Distributed Spatial Data in Free, Open Source CockroachDB (blog post)
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