EXPLAIN gives odd results with sub query

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Jamie Blair

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Mar 4, 2015, 8:20:15 AM3/4/15
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Given the query

EXPLAIN select from (select from Vertex) LIMIT 1

I get the results

elapsed: 2514.5999
recordReads
: 1
documentReads
: 1
resultSize
: 1
evaluated
: 1

Given the query took 2.5seconds I would have expected some of those numbers to be a lot higher (recordReads, documentReads, resultSize, evaluated)

Anyone any idea whats going on? Given the issues with the query parser/optimiser I really need some data about whats going on with my queries before they hit production.

Thanks,
Jamie

Luca Garulli

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Mar 5, 2015, 3:10:44 PM3/5/15
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Hi Jamie,
What about the result of:

EXPLAIN select from Vertex

I think the profiler doesn't collect metrics from sub-queries.

Lvc@


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Jamie Blair

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Mar 5, 2015, 3:32:34 PM3/5/15
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Luca,

Thanks for the reply, yes that will return the correct results. However the orientdb way seem to be to use quite a few sub queries (correct me if I'm wrong), so just having the top level EXPLAINed means that its really hard to profile queries until it hits an environment with a large amount of data.

This was why I originally raised it in github issues because I assumed it was a bug. From what you say I'm guessing its a not, but is there any work arounds to get those sort of metrics?

Thanks,
Jamie

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Luca Garulli

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Mar 5, 2015, 3:45:41 PM3/5/15
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+1 to include sub-query result. Please could you open a new issue?

Lvc@

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