Hi J,
To have a composite index, the individual properties also must be indexed so
I believe what they are getting at is there would be 12 index entries but
not in the same index. For the values 'red' and 'blue' for the x property
you would get 4 index entries because each property that is indexed actually
gets two indexes, 1 that is ascending and 1 that is descending. So value
'red' would be indexed twice, once in the ascending index and once in the
descending index. Same for the 'blue' value. For the values 1 and 2 for the
y property you would also get 4 index entries for the same reasoning. Then
for the composite index you would also get 4 index entries for the
permutations: ('red',1) ('blue',1) ('red',2) ('blue',2). For a grand total
of 12 index entries.
I don't believe they explain it correctly since they say "the index must
store 12 values" making it seem like the composite index itself stores the
12 index entries, but I don't believe that is the case and my reasoning
above is the only way I've been able to come up with the 12 entries. Others
may have a different theory on how to come up with 12.
Stephen
On Mon, Feb 7, 2011 at 12:42 PM, J <[email protected]> wrote:
> Under discussion of exploding indexes,
>
> http://code.google.com/appengine/docs/python/datastore/queries.html#Big_Entities_and_Exploding_Indexes
> ,
> the documentation says "To accurately represent these values, the
> index must store 12 property values".
>
> Could someone please enumerate the 12 property values that must be
> stored? It seems I'm missing something.
>
> Thanks.
>
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