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Posted to jira@arrow.apache.org by "Jorge Leitão (Jira)" <ji...@apache.org> on 2020/11/15 15:20:00 UTC
[jira] [Commented] (ARROW-9555) [Rust] [DataFusion] Add inner
(hash) equijoin physical plan
[ https://issues.apache.org/jira/browse/ARROW-9555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17232314#comment-17232314 ]
Jorge Leitão commented on ARROW-9555:
-------------------------------------
Thanks [~andygrove]. I consider this node kind of important, so I will give it a go.
> [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
> Priority: Major
> Labels: pull-request-available
> Time Spent: 40m
> 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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