This PR implements non-blocking updates in the park layer.
The approach was to use the `REFRESH MATERIALIZED VIEW CONCURRENTLY` feature in postgres. In order to achieve this, a unique index was added on the z4 dissolved park area table. The `ST_Union` / `ST_Dump` sequence was changed to an explicit cluster DB scan (an equivalent operation) so that a unique osm ID could be generated from each dissolved polygon.
Below is a screen shot from Idaho, USA showing that the dissolved z4 still works as expected.
This PR fixes a bug in the park polygon update code introduced in #1160. Because park polygons at zoom 4 are dissolved, the centroid is not present in the table at that layer. Thus, a separate update trigger is needed to avoid errors. This PR adds the separate trigger for the zoom 4 park layer.
This PR likely resolves an unidentified blocker for #1245
I would like to reformat all of our SQL to have a concise coding style.
This makes it far easier to understand the code for a casual contributor,
and lets us spot errors more easily.
Most importantly, it makes it much easier to grep (search) the code because it is more likely to be in the same syntax
Some key changes:
* SQL keywords are always UPPERCASE, e.g. `SELECT WHEN AS END ...`
* types, variables, aliases, and field names (identifiers) are always lower case
* `LANGUAGE 'plpgsql'` is now `LANGUAGE plpgsql` (no quotes)
* a few minor spacing/semicolon cleanups
P.S. Per @TomPohys request, `TABLE` is spelled using upper case despite being a type for consistency with PG Docs. Same for `LANGUAGE SQL` vs `LANGUAGE plpgsql`.
benedikt-brandtner-bikemap
