Protocol version downgrade support in Delta Tables #2061
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Which Delta project/connector is this regarding?
Description
Currently, we support Protocol downgrade in the form of feature removal but downgrading protocol versions is not possible. This PR adds support for protocol version downgrade. This is only allowed for tables that support either reader+writer table features or writer table features. The protocol downgrade takes place when the user removes a table feature and there are no non-legacy table features left in the table. The protocol is downgraded to the minimum reader/writer versions required to support all enabled legacy features.
For example,
Protocol(3, 7, readerFeatures=(DeletionVectors), writerFeatures=(DeletionVectors, ChangeDataFeed)is downgraded toProtocol(1, 4)after removing the DeletionVectors table feature.How was this patch tested?
Added tests in
DeltaProtocolVersionSuiteandDeltaTableFeatureSuite.Does this PR introduce any user-facing changes?
The protocol versions are downgraded when there are non-legacy features in the table.