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https://issues.apache.org/jira/browse/SPARK-57468?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun updated SPARK-57468:
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Parent: SPARK-56754
Issue Type: Sub-task (was: New Feature)
> Extend SQL query plan API to support custom ColumnarBatch types
> ---------------------------------------------------------------
>
> Key: SPARK-57468
> URL: https://issues.apache.org/jira/browse/SPARK-57468
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 4.3.0
> Reporter: Hongze Zhang
> Priority: Major
>
> h3. Summary
> This is a proposal to extend Spark's SQL query plan API to support custom
> ColumnarBatch types.
> h3. Background
> Currently, Spark has 3 different built-in ColumnarBatch types: on-heap,
> off-heap, and Arrow. At the same time, there are many Spark SQL plugin
> projects that have their own ColumnarBatch implementation. However, Spark is
> unable to identify and handle them well during the query planning phase.
> For example, Spark's `RowToColumnarExec`[1] can only convert InternalRow to
> Spark's builtin column vectors, making rule
> `ApplyColumnarRulesAndInsertTransitions` useless for project like Apache
> Gluten on adding row-to-columnar transitions, because the project relies on
> custom vector types.
> For another example, Spark doesn't have `ColumnarToColumnar` transition to
> convert vectorized data among different types. E.g., {*}between Spark Parquet
> / Orc vectors and Arrow vectors{*}, or custom vector types if 3rd plugin is
> used.
> h3. Goal
> The goal is to extend Spark's capability on handling multiple / custom
> ColumnarBatch types, to empower the downstream SQL plugins, making them much
> easier to integrate their own vectorized data layouts with Apache Spark.
> Meanwhile, making them possible to work together (e.g., Gluten + Lance) under
> the same standardized specification, without substantial design conflicts.
> h3. The Change
> To achieve the above goal, the proposed solution is to add a `convention` API
> to `SparkPlan`, consisting of `RowType` / `BatchType` to let the query
> planner know the concrete data layout that this plan node consumes / produces.
> The shape can be very similar to the `GlutenPlan` API[2] in Apache Gluten,
> but optimized and modified towards Spark's code base.
> `RowType` / `BatchType` can be registered along with their supported
> transitions, e.g.,
> {code:scala}
> object VeloxBatchType extends Convention.BatchType {
> override protected def registerTransitions(): Unit = {
> fromRow(Convention.RowType.VanillaRowType, RowToVeloxColumnarExec.apply)
> toRow(Convention.RowType.VanillaRowType, VeloxColumnarToRowExec.apply)
> }
> }
> {code}
> All registered transitions will become a graph, which is being searched in
> `ApplyColumnarRulesAndInsertTransitions`, to determine the final transition
> combinations inserted in between adjacent query plan nodes.
> The API should be treated stable as soon as possible after a few development
> cycles.
> h3. Test / Integration
> The API should be tested solely in Spark's code with mocked RowType /
> ColumnarTypes. Apache Gluten can integrate with this API timely when it's
> ready. We will also work with other SQL plugins to propose essential changes
> to integrate.
> [1]
> [https://github.com/apache/spark/blob/8cd1be4fb380429dec536da2629ba88b6ebc39d3/sql/core/src/main/scala/org/apache/spark/sql/execution/Columnar.scala#L494-L511]
> [2]
> [https://github.com/apache/gluten/blob/2dcee79e3105607bbc83af4e98e08531dc3fce59/gluten-core/src/main/scala/org/apache/gluten/execution/GlutenPlan.scala#L45-L79]
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