(partially) support column mapping #174
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This initial PR offers partial support for column mapping. To achieve this, we parse the transformation expression provided by kernel to get the mapping for each file.
This PR adds:
The main limitation is that this does not yet support nested field mapping. This currently isn't possible in DuckDB's MultiFileReader API in a sensible way. We are however planning to refactor the MultiFileReader(MFR) API for DuckDB v1.3.0 to ensure this is possibly to do quite easily. This refactor should also make this whole process much more understandable because it's currently a serious mental exercise to wrap your head around column mapping for nested types in DuckDB. It will bring the MFR API much closer to what the delta kernel wants us to do with the read schema's and transformations.