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Ensure Nested Loop Join output follows probe order #10651

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Ensure Nested Loop Join output follows probe order #10651

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3 changes: 2 additions & 1 deletion velox/core/PlanNode.h
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Expand Up @@ -1669,7 +1669,8 @@ class MergeJoinNode : public AbstractJoinNode {
///
/// Nested loop join supports both equal and non-equal joins. Expressions
/// specified in joinCondition are evaluated on every combination of left/right
/// tuple, to emit result.
/// tuple, to emit result. Results are emitted following the same input order of
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@mbasmanova mbasmanova Aug 5, 2024

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It would be nice to also update documentation in https://facebookincubator.github.io/velox/develop/operators.html#nestedloopjoinnode

Should we clarify that the order is preserved only within a single thread of execution?

/// probe rows for inner and left joins, for each thread of execution.
///
/// To create Cartesian product of the left/right's output, use the constructor
/// without `joinType` and `joinCondition` parameter.
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4 changes: 3 additions & 1 deletion velox/docs/develop/operators.rst
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Expand Up @@ -562,7 +562,9 @@ NestedLoopJoinNode
NestedLoopJoinNode represents an implementation that iterates through each row from
the left side of the join and, for each row, iterates through all rows from the right
side of the join, comparing them based on the join condition to find matching rows
and emitting results. Nested loop join supports non-equality join.
and emitting results. Nested loop join supports non-equality joins, and emit output
rows in the same order as the probe input (for inner and left outer joins) for each
thread of execution.

.. list-table::
:widths: 10 30
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