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From vkulichenko <valentin.kuliche...@gmail.com>
Subject Re: Affinity key in SQL execution
Date Mon, 27 Aug 2018 20:18:40 GMT
Hi Prasad,

1. First plan is for map phase (executed on server side) and the second one
is for reduce phase (executed on client side). Merge scan means that it just
merges result sets from all participating server nodes. Sometime it can
contain additional reduce steps like final groupings, ordering, etc.

2. This sounds like index is not actually declared correctly and doesn't
exist. Most likely this is reason why Ignite doesn't use it automatically as
well. Please show your full indexing configuration.

3. Of course you can, it can participate in any indexes as any other field.
Individual index for affinity key field is created automatically.

4. Unfortunately, I don't think there is a way to check this except
debugging the code.

5. That depends on what is the foreign key. As a matter of fact, I'm a bit
confused by the query. Looks like the affinity key is not the one you join
on. That means that join is not collocated which is likely to cause
performance issues and/or incorrect results.

6. Can you give a particular query example?

-Val



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