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From Denis Magda <dma...@apache.org>
Subject Re: EXPLAIN for DML statements
Date Fri, 23 Dec 2016 18:36:34 GMT
This might be a tricky part for the users because they need to recreate the query manually

> UPDATE Person SET name = 'John' WHERE surname = 'Smith',
> 
> then we could show
> 
> EXPLAIN SELECT _key from Person WHERE surname = 'Smith’;

How difficult is to support EXPLAIN for DML in general? Let’s discuss the challenges and
implementation details and create a ticket after that.

—
Denis


> On Dec 23, 2016, at 7:46 AM, Alexander Paschenko <alexander.a.paschenko@gmail.com>
wrote:
> 
> Denis,
> 
> Currently there's no API to get those queries. However, they are
> always generated under the hood - except for 'fast' UPDATE and DELETE
> that don't need any queries.
> So what is suggested in docs is to EXPLAIN those SELECTs - say, if we
> have DML statement
> 
> UPDATE Person SET name = 'John' WHERE surname = 'Smith',
> 
> then we could show
> 
> EXPLAIN SELECT _key from Person WHERE surname = 'Smith';
> 
> - Alex
> 
> 2016-12-23 3:09 GMT+03:00 Denis Magda <dmagda@apache.org>:
>> Alex P., Sergi,
>> 
>> All we know that EXPLAIN is not supported for DML statements at the moment.
>> http://apacheignite.gridgain.org/docs/dml#section-explain-support-for-dml-statements
>> 
>> However, I can’t get how I can get over this limitation for UPDATE and
>> DELETE statements following this recommendation
>> 
>> "One possible approach is to execute EXPLAIN for the SELECT automatically
>> generated (UPDATE, DELETE) or used (INSERT, MERGE) by DML statements. This
>> will give an insight on the indexes that are used while a DML operation is
>> executed.”
>> 
>> How can I get SELECT queries that are generated by these DML operations
>> automatically?
>> 
>> —
>> Denis


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