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From Joel Bernstein <>
Subject Re: Joining more than 2 collections
Date Tue, 02 May 2017 18:03:35 GMT
Yes you join more then one collection with Streaming Expressions. Here are
a few things to keep in mind.

* You'll likely want to use the parallel function around the largest join.
You'll need to use the join keys as the partitionKeys.
* innerJoin: requires that the streams be sorted on the join keys.
* innerHashJoin: has no sorting requirement.

So a strategy for a three collection join might look like this:

innerHashJoin(parallel(innerJoin(bigStream, bigStream)), smallerStream)

The largest join can be done in parallel using an innerJoin. You can then
wrap the stream coming out of the parallel function in an innerHashJoin to
join it to another stream.

Joel Bernstein

On Mon, May 1, 2017 at 9:42 PM, Zheng Lin Edwin Yeo <>

> Hi,
> Is it possible to join more than 2 collections using one of the streaming
> expressions (Eg: innerJoin)? If not, is there other ways we can do it?
> Currently, I may need to join 3 or 4 collections together, and to output
> selected fields from all these collections together.
> I'm using Solr 6.4.2.
> Regards,
> Edwin

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