13.08.2013 10:07, Dmitry Yemanov wrote:
> Select Expression
> -> Aggregate
> -> Sort (unique)
> -> Sort (unique)
> -> Table "RDB$RELATIONS" Access By ID
> -> Index "RDB$INDEX_0" Scan
> Is it understandable that sorts are independent from each other but both
> dependent from the retrieval? I don't think so.
In this case for understandability I would suggest to reverse output order:
Select Expression
-> Index "RDB$INDEX_0" Scan
-> Table "RDB$RELATIONS" Access By ID
-> Sort (unique)
-> Aggregate
-> Sort (unique)
This way it will be clear, IMHO, that index scan is first, feed data into
table access
and then its results are used for both sorts independently.
--
WBR, SD.
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