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https://issues.apache.org/jira/browse/ARROW-9555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andy Grove resolved ARROW-9555.
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Fix Version/s: 3.0.0
Resolution: Fixed
Issue resolved by pull request 8709
[https://github.com/apache/arrow/pull/8709]
> [Rust] [DataFusion] Add inner (hash) equijoin physical plan
> -----------------------------------------------------------
>
> Key: ARROW-9555
> URL: https://issues.apache.org/jira/browse/ARROW-9555
> Project: Apache Arrow
> Issue Type: Sub-task
> Components: Rust - DataFusion
> Reporter: Jorge Leitão
> Assignee: Jorge Leitão
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.0.0
>
> Time Spent: 9h 50m
> Remaining Estimate: 0h
>
> Here is an overview of how I think we should implement support for equijoins,
> at least for the initial implementation.
> * Read all batches from the left-side of the join into a single
> Vec<RecordBatch>
> * Create a map something like HashMap<Vec<ScalarValue>, Vec<(usize,usize)>>
> to map keys to batch/row indices
> * Iterate over this Vec<RecordBatch> and create an entry in a hash map,
> mapping the join keys to the index of the batch and row in the
> Vec<RecordBatch>
> * For each input partition on the right-side of the join, return an output
> partition that is an iterator/stream that:
> ** For each input row, evaluate the join keys
> ** Look up those join keys in the hash map
> ** If a match is found:
> *** For each (batch, row) index create an output row which has the values
> from both the left and right row and emit it
> ** If no match is found:
> *** Do not emit a row
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