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Yifan Mai commented on BEAM-11196: ---------------------------------- Summarizing an an offline conversation with [~robertwb]: If you fuse two stages without a common parent, currently the parent gets set to `None` i.e. it gets promoted to a root transform. This is problematic because in [some places|https://github.com/apache/beam/blob/eeb1497875bd9f9ae1be60e4b8d2d05dd834064e/sdks/python/apache_beam/pipeline.py#L892] we assume that there is exactly one root transform. Instead we should set the parent to the lowest common ancestor. > Composite transform structure not preserved with fusion. > -------------------------------------------------------- > > Key: BEAM-11196 > URL: https://issues.apache.org/jira/browse/BEAM-11196 > Project: Beam > Issue Type: Bug > Components: sdk-py-core > Reporter: Robert Bradshaw > Assignee: Yifan Mai > Priority: P2 > Fix For: 2.26.0 > > > This causes problems with combiner packing, among other things. -- This message was sent by Atlassian Jira (v8.3.4#803005)