Overpass API developpement

[mmd <>]

Hi,

Am 20.09.2017 um 22:12 schrieb marc marc:

> 
> I tried with --flush-size=6 and the import succeeded
> 
> what is the exact meaning of --flush-size = 1 ? a flush after each 
> modified node/way/relation ? after each tag ? each changeset ?
> 
> Is it a "formula" between flush-size and maximum consumed ram ?
> I imagine something like x Mo + x Mo x flush-size = max malloc ram
> 

update_database.cc has the following definitions:

Default value: flush_limit = 16*1024*1024

When setting --flush-size=6 as a parameter, flush_limit will be set to
6*1024*1024.

Very roughly speaking, when importing nodes/ways/relations, the number
of objects will be counted, and once the flush-size threshold is
reached, objects will be flushed to disk and the counter reset to zero.
As objects have varying sizes, this is a rough approximation of the
actual memory requirements.

The smaller the flush size value, the more ofter you need to flush to
disk, and possibly read referenced objects (especially nodes) more often
from disk - which would otherwise still be in memory. Setting it close
to the maximum value your memory permits reduces the overall runtime of
the initial load.


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