[Tilesathome] t at h server performance

[Milenko]

Pardon my ignorance, but what is the purpose of this database of blank 
tiles?  I'm just curious, as I know little to nothing about what the t at h 
server does and how it does it.  Is there a wiki page anywhere that explains 
how the infrastructure works?

-Jeremy

----- Original Message ----- 
From: "Martijn van Oosterhout" <kleptog at gmail.com>
To: "Christopher Schmidt" <crschmidt at metacarta.com>
Cc: <tilesathome at openstreetmap.org>
Sent: Saturday, December 22, 2007 10:35 AM
Subject: Re: [Tilesathome] t at h server performance


> On Dec 22, 2007 3:43 PM, Christopher Schmidt <crschmidt at metacarta.com> 
> wrote:
>> In the long term, we need to come up with some more efficient way of
>> storing blank tiles than the current database.
>
> It should be said that we arn't using the current format as
> efficiently as possible. For example, we could make the clients
> produce less blank tiles, and we could get the server to store them
> more efficiently, we're not taking full advantage of the fallback
> system. Some random ideas:
>
> - Clients create a blank sea/land tile whenever they find something
> blank. The client could immediately check to see if the tile above it
> is also blank and if so store a 0-byte file instead. That's one less
> entry in the DB to clean up later.
> - When the server has the list of blank tiles to insert, it could run
> one pass over the list to see if it's mostly sea of mostly land and
> whatever it is, insert a blank tile with that type at zoom-12 and then
> only insert the other types.
>
> The latter idea is I think where we could make some real gains bt it's
> currently impossible to do on the client side because client only have
> the option of uploading a blank tile *or* a real tile at zoom-12, not
> both.
>
>> For the record, I ran the cleanblanktiles script yesterday, so the blank
>> tile db is as clean as that code makes it. I don't know if there are
>> further optimizations that can be made there -- perhaps someone else can
>> comment -- but I've done everything I know how to do.
>
> I'd never looked at the cleanblanktiles before but it certainly looks
> like its missing some possible optimisations. Especially my second
> suggestion above would remove many z17 blank tiles, which are half the
> current DB.
>
> Have a nice day,
>
> -- 
> Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/
>
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