Implemented ordering for expanded iterators #8741
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Added a test for nested iterator execution ordering. (Failing at commit time!)
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When a graph has nested iterators, some "ready to run" node combinations do not actually belong together. Previously, the scheduler would still try to build nodes for those mismatched combinations, which could cause the same work to run more than once. This change skips any combination that is missing a valid iterator parent, so nested iterator expansions run once per intended item.
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lstein
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Jan 11, 2026
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I'd like to be able to review this PR, but I've never quite understood how to use the collection/iteration functions in the workflow editor and don't think I have the expertise to identify edge cases and so forth.
If no one else is able to review, I'll come up to speed and give it a shot.
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Summary
Feature: best-effort in-order execution for nodes expanded by
IterateInvocation, subject to ready state.Why: iteration-expanded work could run in an arbitrary order when multiple iteration branches become ready at the same time, which reduces determinism and makes behavior harder to reason about.
How: compute a cached per-exec-node "iteration path" (outer to inner indices for nested iterators, respecting collector boundaries) and use it to ordered-insert ready nodes into the existing per-class ready queues. FIFO is preserved for equal iteration paths, and no blocking is introduced.
Related Issues / Discussions
QA Instructions
Create a collection, note the ordering, then iterate and pass values to a series of other nodes. Check that the outputs use the source collection's items in order.
Merge Plan
Checklist
What's Newcopy (if doing a release after this PR)