Anish Mahto created SPARK-57378:
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Summary: Implement SCD2 Batch Processor; Merge Reconciled Rows
into Aux and Target Tables
Key: SPARK-57378
URL: https://issues.apache.org/jira/browse/SPARK-57378
Project: Spark
Issue Type: Sub-task
Components: Declarative Pipelines
Affects Versions: 4.3.0
Reporter: Anish Mahto
{*}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.
*Merge Reconciled Rows into Aux and Target Tables*
Once we have the full set of rows affected by the incoming microbatch in their
post-reconciliation state, with redundant rows dropped, we're ready to persist
this set of rows back to the aux/target tables.
This is three step process:
# Tag whether a row should land in the aux or target table, depending on what
type of row it is. No-op upserts and tombstones go to aux, op upserts go to
target table.
# Merge rows headed for the aux into the aux table. Drop rows from the aux if
they have been promoted to the target table or made redundant
# Merge rows headed for the target table. Drop rows from the target table if
they have been demoted to the aux table.
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