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Robert Bradshaw updated BEAM-11355: ----------------------------------- Resolution: Fixed Status: Resolved (was: Open) > pipeline_from_stages after sort_stages can return non-topologically ordered > pipelines > ------------------------------------------------------------------------------------- > > Key: BEAM-11355 > URL: https://issues.apache.org/jira/browse/BEAM-11355 > Project: Beam > Issue Type: Bug > Components: sdk-py-core > Reporter: Yifan Mai > Assignee: Yifan Mai > Priority: P2 > Time Spent: 1h > Remaining Estimate: 0h > > translations.sort_stages() sorts stages in topological order. However, > calling translations.pipeline_from_stages() on sorted stages can result in a > pipeline that is not topologically ordered. This is because of how it > constructs the tree of parent to subtransforms. > Example pipeline: > * Leaf transforms are A, B and C. > * Composite transform D has subtransforms B and C. > * Root transform E has subtransforms A and D. > * A produces an output that is an input to C, and B produces an output that > is an input to C. > * After optimizations and sort stages, the order of leaf stages is B, A, C > (this is a valid ordering) > Under the current implementation of translations.pipeline_from_stages(): > # B is added to the pipeline first, which also adds its parent D and its > grandparent E to the pipeline. D is added as the first subtransform of E and > B is added as the first subtransform of D. > # A is added to the pipeline second. A is added as the second subtransform > of E. > # C is added to the pipeline third. C is added as the second subtransform of > D. > The order is now E(D(B, C), A) which is invalid because C must follow A. A > valid order would be E(A, D(B, C)). > The easiest fix is to change translations.pipeline_from_stages() such that > whenever a leaf transform is added to the pipeline, all its ancestors are > moved to the last position of the subtransforms of their respective parent. -- This message was sent by Atlassian Jira (v8.3.4#803005)