OrElseCursor doesn't properly support continuations #974
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nschiefer
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Jun 17, 2020
…ations. Use a new structured continuation object and protobuf serialization to record the complete state of the OrElseCursor, including which branch was chosen. Rewrite OrElseCursor's logic in a simpler state-machine style, which makes it easy to resume the cursor before it has made a decision about which branch to take. To avoid problems like we saw with the FlatMapPipelinedCursor's continuations, deprecate the RecordCursor.orElse() fluent method and replace it with a static method that interprets the continuation. Because this changes the continuation format, this is a breaking change.
alecgrieser
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Jun 17, 2020
Fixes #974: OrElseCursor doesn't properly support continuations.
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An
OrElseCursoris built out of an "inner" cursor and and an "else" cursor. If the inner cursor is non-empty, it returns values from the inner cursor; otherwise, it returns the values from the else cursor.Currently, the
OrElseCursoruses pass-through style continuation handling. However, this loses information (specifically: which branch the cursor is using). As a result, if the cursor chooses the else branch, there is no way to continue the cursor's operation.To resolve this, we probably need to give
OrElseCursora structured protobuf continuation, likeFlatMapPipelinedCursor.The text was updated successfully, but these errors were encountered: