Eliminate Unused Response Artifacts

[DurstDog87]

Problem:

geom is required by ST_AsMVTGeom to create an envelope from which to form tiles. However, geom then remains as an artifact in the query output sent out to the client.

Example:

WITH mvtgeom AS (
            SELECT ST_AsMVTGeom(ST_Transform(geom, 3857), ST_TileEnvelope(
                    1,1,1
                )) AS mvtgeom, *
            FROM (SELECT gid, geom FROM sch.table) AS dat --geom included in query is used by ST_AsMVTGeom
            WHERE ST_Intersects(geom, ST_Transform(ST_TileEnvelope(
                    1,1,1
            ), 4269))
        )
        SELECT ST_AsMVT(mvtgeom.*) AS mvt FROM mvtgeom; --geom included in output tuple

resulting output tuple will include both gid and geom [(<gid>, <geom>), ...]. This means more bytes sent to the client, even if they are never used.

Solution:

• eliminate geom from output? How? But then how do we add it back if it is actually wanted?
• leave as is? But then we are potentially sending more data to the client than is actually needed.