Hello all,
I am trying to formulate a query for the group-wise maximum/minimum on a
single class in OrientDB (was initially working with version 2.1.0
release). However, I haven't been able to make a reasonable query to do
it...
My first attempt looked like:
select max(tx),@rid,name,valid from Test group by name
where the test schema was:
class Test {
"name" : string,
"tx" : integer,
"valid" : boolean
}
However, this didn't work, since OrientDB doesn't return the correct record
for the @rid and valid fields associated with the max tx field (it doesn't
work for most other RDBMs either; see Database Journal / SQL Antipatterns
<http://www.databasejournal.com/features/mysql/article.php/3893756/SQLAntipatterns-Avoiding-the-Pitfalls-of-Database-Programming.htm>,
and multiple issues on StackOverflow). I commented on this issue
<https://github.com/orientechnologies/orientdb/issues/2585> the other day,
and have actually attempted to modified OrientDB to support this specific
use case (see commit 56324ec
<https://github.com/jlowenz/orientdb/commit/56324ec229fd4d0d49af2da4b9f85efcaee9e910>
).
However, OrientDB doesn't support joins (the solution for the other DBs),
so after trial and error I formulated the following query:
select * from Test let $parms=(select name,max(tx) from Test where name=
$parent.current.name) where $parms[0].max = tx
but this is REALLY slow (I get why - basically running the LET query for
every record). I built some test code, and the average time for this query
is 12 seconds for 1600 records (100 names plus 16 tx values each). In
contrast, the modified min/max record selection code yields an average 31
*milliseconds*.
I was wondering if anyone here has a way to do this? It seems like I must
be missing something obvious, and I'd appreciate any help on this.
BTW - running test in orientdb.core is taking forever in the *develop*
branch.
Thanks,
-Jason
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