This database functions add a 'multipolygons' to an osmosis pgsnapshot database schema.

INSTALL

• First import your database using osmosis. Make sure that the 'ways' table has linestrings.
• Load the database functions:

psql -f upgrade.sql # skip for new installs
psql -f assemble_multipolygon.sql
psql -f build_multipolygon.sql
psql -f make_multipolygon.sql
psql -f tags_merge.sql
psql -f update.sql
psql -f create.sql
psql -f assemble.sql

• The 'osmosisUpdate' database function will be overridden, so that changesets can be imported to the database and the multipolygons table will automatically be updated.

DATA

The 'multipolygons' table looks like this:

id | tags | has_outer_tags | hide_outer_ways | geom ------------|---------------|--------------------------|----------------- 75 | "name"=>"Untere Alte Donau", "type"=>"multipolygon", "water"=>"oxbow", "natural"=>"water" | f | null | 0103000020E61000000... 11154 | "name"=>"Rossauer Kaserne", "type"=>"multipolygon", "source"=>"wien.gv.at", "alt_name"=>"Rudolfskaserne", "building"=>"yes", "military"=>"barracks", "wikipedia:de"=>"Rossauer Kaserne" | f | null | 0103000020E61000000... 27945 | "name"=>"HLTW13", "type"=>"multipolygon", "amenity"=>"school", "building"=>"yes", "created_by"=>"Potlatch 0.10b" | t | {26350742} | 0103000020E61000000... 121006 | "type"=>"multipolygon", "source"=>"ViennaGIS", "building"=>"yes" | f | {33720939} | 0103000020E61000000...

Table colums:

name	type	description
id	bigint	ID of the relation which defines this multipolygon
tags	hstore	A hstore (a key-value datatype) containing all tags of the multipolygon, either of the relation itself or mixed with the tags of the outer way(s) (see has_outer_tags).
has_outer_tags	boolean	A boolean indicating whether the tags of the relation itself has been used (false) or if the tags of the outer ways(s) has been mixed into it.
hide_outer_ways	bigint[]	Contains list of IDs of the outer ways, if they should be hidden from rendering (because the tags were taken from these ways (has_outer_tags=true) or the tags of the outer ways and the relation itself are equal (has_outer_tags=false)). null, if no ways should be hidden.
geom	geometry	The geometry of the object.

Notes:

• Tags of the outer ways will be mixed into the tags of the relation if the relation has no relevant tags and all outer ways have equal tags (not including non-relevant tags).
• Relevant tags are all tags, short of 'source', 'created_by', 'fixme', …. For a full list see the variable non_relevant_tags at the beginning of the assemble_multipolygon function.
• If a (non relevant) tag is present on several objects with different value, those will be merged by semi colons, e.g. created_by=>"Potlatch 0.10b;Merkaartor 0.12".

HISTORY

These scripts are based on some OpenStreetBrowser code, which added multipolygon support for the osmosis pgsimple database schema. See https://github.com/plepe/OpenStreetBrowser-database for details.

It's actually pretty old code, which I'm not too proud of. But it does its job and maybe it can help someone.