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https://issues.apache.org/jira/browse/SPARK-57222?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated SPARK-57222:
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Labels: pull-request-available (was: )
> Implement SCD2 Batch Processor; Decompose affected rows
> -------------------------------------------------------
>
> Key: SPARK-57222
> URL: https://issues.apache.org/jira/browse/SPARK-57222
> Project: Spark
> Issue Type: Sub-task
> Components: Declarative Pipelines
> Affects Versions: 4.3.0
> Reporter: Anish Mahto
> Priority: Major
> Labels: pull-request-available
>
> {*}Preamble{*}:
> The SCD type 2 flow is a foreachBatch streaming query on an input
> change-data-feed, and is responsible for reconciling the incoming change data
> onto some target table that follows SCD2 replication semantics.
> SCD2 flows also maintain an "auxiliary" table to keep track of early-arriving
> out-of-order received events state. Each microbatch will need to reconcile
> against this auxiliary table as well, and update the auxiliary table's state
> appropriately for future microbatches.
>
> *Decompose affected rows*
> Given the set of affected rows in the current microbatch execution - incoming
> rows in the microbatch, affected rows from aux table, affected rows from
> target table - the first step in microbatch reconciliation is decomposing
> closed historical rows that are being bisected by the microbatch.
> A closed historical row is a row in the target table that has a non-null
> start-at and end-at. It's possible an incoming upsert/delete in the
> microbatch lands with a sequence in between an existing closed row's
> start/end at (i.e is a late-arriving event), bisecting it.
> Decomposing a closed row means exactly this - bisecting the closed interval
> into a left and right end point, called the decomposed head and tail of the
> original closed row respectively. The head represents some past upsert event,
> the tail represents some past delete event.
> Once a closed row is decomposed into its end points, it can either coalesce
> with other endpoints/events from the full set of affected rows to form a new
> historical row, or it can be demoted back to the aux table as a tombstone or
> no-op upsert.
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