[jira] [Created] (IMPALA-15171) NULL out INPUT__FILE__NAME in IcebergDeleteNode if not needed downstream

["Zoltán Borók-Nagy (Jira)" <ji...@apache.org>]

Zoltán Borók-Nagy created IMPALA-15171:
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             Summary: NULL out INPUT__FILE__NAME in IcebergDeleteNode if not needed downstream
                 Key: IMPALA-15171
                 URL: https://issues.apache.org/jira/browse/IMPALA-15171
             Project: IMPALA
          Issue Type: Improvement
          Components: Backend, Frontend
            Reporter: Zoltán Borók-Nagy


pala's IcebergScanPlanner.addDataVirtualPositionSlots() materializes the INPUT__FILE__NAME (file path) virtual column on the data-scan tuple so the IcebergDeleteJoinNode can use it as a position-delete join key.

When the user's query doesn't otherwise need it, the slot is still carried in the join's output tuple and propagates through every downstream EXCHANGE, where the (long, per-data-file) file-path string is deep-copied and serialized on every surviving row — pure overhead.

*Proposed fix*

Have the planner detect whether it created the INPUT__FILE__NAME slot itself (vs. the user/DML already referencing it) and, if so, tell the backend to NULL it out on the delete join's output rows.

{*}Frontend{*}:
  - In addDataVirtualPositionSlots(), probe analyzer.getSlotDescriptor(resolvedPath) == null before adding the slot. All user/DELETE/UPDATE/MERGE references to INPUT__FILE__NAME are registered during analysis (before planning), so "absent" reliably means "no operator above the join needs it."
  - If planner-created, pass the slot id to IcebergDeleteJoinNode via a new TIcebergDeleteNode field.

{*}Backend{*}:
  - In iceberg-delete-node.cc ProcessProbeBatch(), SetNull() the flagged slot on output rows. This is safe (node never re-reads emitted rows) and NULLing a var-len string slot skips both the deep copy and the wire serialization (Tuple::DeepCopyVarlenData / VarlenByteSize guard on the null bit).



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