Big polyfile extents lead to timeout

Created by: hixi

Using very large polyfiles leads to:

• a timeout on server
• unstartet extraction

Possible solutions:

• reduce too big polyfiles geometries using a buffer and simplify.
• instead of on-the-fly-adding buffer use a precomputed one
• use subregions of the too big polyfiles, which might not necessarily be smaller
• Use only verified polyfiles. ie. Brittany gives an error sqlalchemy.exc.InternalError: (psycopg2.InternalError) GEOSIntersects: TopologyException: side location conflict at -3.3223849914347121 48.843851070663817 on the worker side
• use signals or similar process to start the process so the user gets an answer before the conversion is actually started
• curated polyfiles by OSMaxx-Team: simplify polyfiles before adding; add limit to number of points for polyfile (inclusive buffer?).

A good example is France - Brittany