Every entity stores the full property name for every property defined
on that model.  So if you have long property names it takes a lot of
space.  On models with only numbers, booleans, and short strings we
often see metadata make up 50%+ of a models, unless we use really
short property names (2 char).

The difference between your 705MB and 2.31GB is probably due to
indexes.  Unfortunately indexes are not accounted for on the Datastore
Stats page.  In one of our apps we have a lot of composite indexes,
our 'total storage' is approximately 10x the 'total size of entities'
reported on the stats page.

There are a lot of threads discussing these topics if you want more
info.  There is also an article that explains how the entity storage
works:
http://code.google.com/appengine/articles/storage_breakdown.html


Robert








On Fri, Mar 5, 2010 at 9:12 PM, PK <[email protected]> wrote:
> The "datastore statistics" is a great concept. However, I consistently
> see that the majority of my space goes to metadata. From other
> postings I see that I am not the only one. Here is an example from my
> application that contains roughly 15,000 entities:
>
> Breakdown by Property Type Property Type        Size
> Blob    11 MBytes
> String  5 MBytes
> Integer         2 MBytes
> Key     2 MBytes
> NULL    726 KBytes
> Date/Time       705 KBytes
> Text    461 KBytes
> Boolean         13 KBytes
> GeoPt   5 KBytes
> Metadata        683 MBytes
>
> The breakdown is really not useful when it breaks down the 3% of the
> space while the 97% of the space is consumed by metadata that I cannot
> drill into!!!!!
>
> Based on previous postings on what metadata is, I am wondering, are
> the protocol buffers so inefficient? Can this be related to exploding
> indexes and if yes how is this possible, do metadata account for
> composite indexes as well? Any advice on how to troubleshoot this
> issue?
>
> One more question, the size of my entities is reported as 705MB,
> however the dashboard shows that I use 2.31GB. Is the difference
> between these two figures the size of the composite indexes?
>
> Thanks
>
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