Hello everyone,
after experiencing database stability issues with postgis since the end
of July, which made using the OpenStreetMap database more or less
impossible, we have finally managed to identify the issues and have
hopefully found a stable workaround.
After a full re-import of the data, the OpenStreetMap database on
Ptolemy is now back up-to-date. In most cases replication delay to the
main OpenStreetMap database is 5 minutes, but during busy times
typically afternoon to evening European time, the replication delay can
be larger as the server can't always keep up with replication.
With the Database, the services using it, should also be mostly
up-to-date again. This includes WIWOSM, client side rendering in
WikiMiniAtlas and the the tiles in various styles provided by the
toolserver used in e.g. the osm-gadget in a number of Wikipedias. (The
tile rendering is actually still catching up with the backlog of changes
for a while).
Any other services using the database should also be up-to-date again,
and everyone who has a toolserver account should, as previous, be able
to read-access the database via "psql -h sql-mapnik -d osm_mapnik" from
any of the toolserver login servers if they want to experiment with the
OpenStreetMap data.
The initial issue with the crashing database turned out to be a problem
with PostGIS. The function ST_Intersection crashes postgresql if it
operates on invalid polygons (e.g. self intersecting polygons). As the
OpenStreetMap data model is very flexible and lenient, nothing stops
people from entering invalid polygons and the import tools currently
don't filter these out. So the database contains quite a few invalid
polygons that can cause issues with PostGIS.
In future we might fix the import tools to exclude invalid polygons to
begin with, but for now everyone who uses the database will need to use
the following workaround: When ever you use a query on the
planet_polygon table, you should add a "where ST_IsValid(way)" condition
to the query to ensure it only processes valid geometries.
If anyone still experiences any issues, please let me know.
Kai