Add custom index information

[pnorman]

These custom indexes should speed up rendering, particularly at low and middle zooms.

Fixes #207

cc @woodpeck @jburgess777 @Firefishy

I'm not recommending any way_area indexes, not because I don't think they're worth it, but because they're more complicated to get right, and I'd rather go ahead and recommend a number of indexes I already know help performance.

[pnorman]

Suggested to me was an index for low zoom admin polygons to reflect the switch to OSM data for low zoom labeling. My benchmarking was prior to this, but I recall it being a good idea.

[rrzefox]

The IF NOT EXISTS will only work for postgresql >= 9.5. 9.4 or older do not have it (so in particular, the 9.3 in ubuntu 14.04 does not have it).

[pnorman]

The IF NOT EXISTS will only work for postgresql >= 9.5. 9.4 or older do not have it (so in particular, the 9.3 in ubuntu 14.04 does not have it).

Updated.

[pnorman]

This index is 653MB and only used by text-point, so I'm not this is worth the additional memory cache pressure.

[pnorman]

I have a WIP changing how these are defined to allow creation of SQL statements to reindex, etc.

[pnorman]

• indexes.sql is now a generated file, but shouldn't need to be changed much
• The script options are

  -h, --help            show this help message and exit
  --concurrent          Generate indexes CONCURRENTLY
  --fillfactor FILLFACTOR
                        Custom fillfactor to use
  --notexist            Use IF NOT EXISTS (requires 9.5)
  --osm2pgsql           Include indexes normally built by osm2pgsql
  --reindex             Rebuild existing indexes

Examples are
default:

CREATE INDEX planet_osm_roads_admin
  ON planet_osm_roads USING GIST (way)
  WHERE boundary = 'administrative';

--fillfactor 100:

CREATE INDEX planet_osm_roads_admin
  ON planet_osm_roads USING GIST (way)
  WITH (fillfactor=100)
  WHERE boundary = 'administrative';

--concurrent:

CREATE INDEX CONCURRENTLY planet_osm_roads_admin
  ON planet_osm_roads USING GIST (way)
  WHERE boundary = 'administrative';

--reindex:

REINDEX planet_osm_roads_admin;

--reindex --concujrrent

ALTER INDEX planet_osm_roads_admin RENAME TO planet_osm_roads_admin_old;
CREATE INDEX CONCURRENTLY planet_osm_roads_admin
  ON planet_osm_roads USING GIST (way)
  WHERE boundary = 'administrative';
DROP INDEX planet_osm_roads_admin_old;

--osm2pgsql simply adds statements for planet_osm_[point|line|polygon|roads]_index

[pnorman]

shouldn't have the WHERE here

[pnorman]

I think this is ready

[matthijsmelissen]

Thanks!