feat: metadata columns #14057
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feat: metadata columns #14057
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logical-expr
jayzhan211
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Jan 10, 2025
| return metadata.qualified_field(i - self.inner.len()); | ||
| } | ||
| } | ||
| self.inner.qualified_field(i) |
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Is it better not to mix inner field and meta field?
maybe we need another method meta_field(&self, i: usize)
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actually implementing another method was my first attempt. but I found that I need to change a lot of code, because column index is used everywhere. that's why in currently implementation metadata column has index + len(fields).
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Which issue does this PR close?
Closes #13975.
Rationale for this change
many databases support pseudo columns, for example, file_path, file_name, file_size, rowid.
for pseudo columns, we don't want to get them by default, but we want to be able to use them explicitly.
for the database that supports rowid.
select * from tbwon't return rowid. but we can get rowid byselect rowid, * from tb. spark has already supported metadata columns. this PR want to support it in datafusion.What changes are included in this PR?
Are these changes tested?
Unit test is added
Are there any user-facing changes?
No
For FFI table provider API, one function that returns metadata column is added.