feat(writer): add change-type splitter for delta writes - #3231
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Introduce the delta_writer module as the first building block for the DeltaWriter epic (apache#2218). Its record_ops::split_by_change_type takes a RecordBatch carrying the repo's _change_type column and splits it into separate insert and delete batches. The _change_type column is located by name (RESERVED_COL_NAME_CHANGE_TYPE), wherever it sits in the schema, and must be a non-nullable Utf8 column whose values are all one of the four spec change types. Following Java's BaseDeltaTaskWriter, INSERT and UPDATE_AFTER rows collapse to inserts while DELETE and UPDATE_BEFORE rows collapse to deletes. The _change_type column is stripped from both outputs, preserving each payload column's field-id metadata and the schema-level metadata; input row order is preserved within each side. Anything violating the contract (missing/mistyped/nullable/null/out-of-domain _change_type, or no payload columns) is rejected as DataInvalid. The module is pub(crate) since nothing wires it into a writer yet (that lands in a later PR of the epic).
laskoviymishka
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September 15, 2026 20:02
anoopj
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Sep 16, 2026
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Sep 16, 2026
anoopj
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Sep 16, 2026
anoopj
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Sep 16, 2026
…visibility, trim docs Replace the manual payload-schema rebuild in split_by_change_type with RecordBatch::project, which drops the change-type column while carrying over each surviving field's metadata (field ids) and the schema-level metadata, instead of reimplementing an existing Arrow primitive. Tighten SplitBatches, its fields, and split_by_change_type to pub(crate), matching the crate-internal delta_writer module and the change-type constants. The module stays behind allow(dead_code) until a writer consumes it. Trim the module docs by dropping the epic link and the building-block comments that would go stale, keeping a one-line module purpose and the split_by_change_type Returns/Errors contract.
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September 23, 2026 19:41
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Which issue does this PR close?
Introduce the delta_writer module as the first building block for the DeltaWriter epic (#2218). Its record_ops::split_by_change_type takes a RecordBatch carrying the repo's _change_type column and splits it into separate insert and delete batches.
The _change_type column is located by name (RESERVED_COL_NAME_CHANGE_TYPE), wherever it sits in the schema, and must be a non-nullable Utf8 column whose values are all one of the four spec change types. Following Java's BaseDeltaTaskWriter, INSERT and UPDATE_AFTER rows collapse to inserts while DELETE and UPDATE_BEFORE rows collapse to deletes. The _change_type column is stripped from both outputs, preserving each payload column's field-id metadata and the schema-level metadata; input row order is preserved within each side. Anything violating the contract (missing/mistyped/nullable/null/out-of-domain _change_type, or no payload columns) is rejected as DataInvalid.
The module is pub(crate) since nothing wires it into a writer yet (that lands in a later PR of the epic).
Are these changes tested?
Newly added tests.