[Tilesathome] another idea for more performance

[Damian Sulewski]

Hi,
here is another idea to analyse.

1. Clients do not upload zoom z+1 blank if zoom z is blank.
2. if server receives a blank_tile it removes all meta info and files
under it from disk, marking only this tile as blank.

Removing all files from disk is done today also, because clients upload
a whole tileset. Removing meta info is in svn will be in asap.

For the switching phase we can decide on "vallidTileset" setting

Advantages: 
- much less REPLACE in tile_blank mysql. 
- REPLACE in tile_meta/deleting does not change.
- lowzoom will be updated to upload only highest zoom levels
- if, one day, the metainfo is accurate, we can decide on deleting if
meta info exists

Dissadvantage: 
- if someone uploads a whole tileset, not telling the server thats a
tileset,  it means a lot of replace and deleting
- if someone uploads an blank tile at zoom 1 there will be much work
lost :-) (currently its the same if someone lowzoom z1 and it decides to
upload only blank tiles)
- sure more to come ;-) 

Greetings,

Damian


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