Matching events between flow versions (data)

[edhinkle]

Different versions of flow may lead to the same data event being assigned different Event IDs. This may occur due to changes in the event building between flow versions or due to differences in flow settings (e.g. only running over beam events). While this feature is expected, it complicates analyzers' ability to compare the same event across different flow reprocessings. In July 2024 2x2 data, this is particularly an issue for beam events, which are expected to be built regardless of flow version. In the case of beam events, the unix timestamp may be used to match events across versions, but events in general are not easily searchable using this parameter across all file types, partly because multiple events (beam + non-beam) may have the same unix timestamp. An example use case where this matching issue caused challenges is documented here.