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From "ASF subversion and git services (JIRA)" <>
Subject [jira] [Commented] (SOLR-8530) Add HavingStream to Streaming API and StreamingExpressions
Date Tue, 03 Jan 2017 22:30:59 GMT


ASF subversion and git services commented on SOLR-8530:

Commit d8a58146c3155a13f9bb8c46eb2d2878301426d3 in lucene-solr's branch refs/heads/branch_6x
from [~joel.bernstein]
[;h=d8a5814 ]

SOLR-8530: Updated CHANGES.txt

> Add HavingStream to Streaming API and StreamingExpressions
> ----------------------------------------------------------
>                 Key: SOLR-8530
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>          Components: SolrJ
>    Affects Versions: 6.0
>            Reporter: Dennis Gove
>            Priority: Minor
>         Attachments: SOLR-8530.patch
> The goal here is to support something similar to SQL's HAVING clause where one can filter
documents based on data that is not available in the index. For example, filter the output
of a reduce(....) based on the calculated metrics.
> {code}
> having(
>   reduce(
>     search(.....),
>     sum(cost),
>     on=customerId
>   ),
>   q="sum(cost):[500 TO *]"
> )
> {code}
> This example would return all where the total spent by each distinct customer is >=
500. The total spent is calculated via the sum(cost) metric in the reduce stream.
> The intent is to support as the filters in the having(...) clause the full query syntax
of a search(...) clause. I see this being possible in one of two ways. 
> 1. Use Lucene's MemoryIndex and as each tuple is read out of the underlying stream creating
an instance of MemoryIndex and apply the query to it. If the result of that is >0 then
the tuple should be returned from the HavingStream.
> 2. Create an in-memory solr index via something like RamDirectory, read all tuples into
that in-memory index using the UpdateStream, and then stream out of that all the matching
tuples from the query.
> There are benefits to each approach but I think the easiest and most direct one is the
MemoryIndex approach. With MemoryIndex it isn't necessary to read all incoming tuples before
returning a single tuple. With a MemoryIndex there is a need to parse the solr query parameters
and create a valid Lucene query but I suspect that can be done using existing QParser implementations.

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