Bertil Chapuis created CALCITE-6239:
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Summary: Add a postgis dialect that supports ST functions
Key: CALCITE-6239
URL: https://issues.apache.org/jira/browse/CALCITE-6239
Project: Calcite
Issue Type: New Feature
Components: core
Reporter: Bertil Chapuis
Calcite implements support for spatial types (geometry, point, etc.) and
spatial functions (ST_), and it can connect to PostGIS via a JdbcSchema.
However, the Postgresql dialect does not currently handle spatial types and
functions. As a result, Calcite tries to execute the spatial functions at the
level of the JVM instead of pushing them down to postgis.
As a result, the following query gets executed, but the type of the geom column
is incorrect:
SELECT id, geom FROM public.spatial_table
The following query fails with a ClassCastException as Calcite tries to use the
java implementation of the ST_SRID function:
SELECT id, ST_SRID(geom) FROM public.spatial_table
java.lang.ClassCastException: class org.postgresql.util.PGobject cannot be cast
to class org.locationtech.jts.geom.Geometry (org.postgresql.util.PGobject and
org.locationtech.jts.geom.Geometry are in unnamed module of loader 'app')
In my current understanding, this issue could be addressed with a new
PostgisSqlDialect that extends PostgresqlSqlDialect and adds support for
spatial types and functions. Here is a tentative roadmap:
- Add all the spatial functions to the SqlKind class
- Create a PostgisSqlDialect class that extends PostgresqlSqlDialect
- Add support for the spatial types (geometry) by overriding the getCastSpec
method of the SqlDialect class
- Add support for the spatial functions by overriding the supportsFunction
method of the SqlDialect class
- Add support for the spatial aggregate functions by overriding the
supportsAggregateFunction method of the SqlDialect class
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