fix: Support dictionary type in parquet metadata statistics. #11169
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appletreeisyellow
approved these changes
Jun 28, 2024
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Thank you for fixing it! @efredine 💯
I left comments in the test to avoid confusions
| assert_eq!(c_dic_stats.null_count, Precision::Exact(0)); | ||
| assert_eq!( | ||
| c_dic_stats.max_value, | ||
| Precision::Exact(Utf8(Some("c".into()))) |
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Suggested change
| Precision::Exact(Utf8(Some("c".into()))) | |
| Precision::Exact(Utf8(Some("d".into()))) |
To avoid any confusion, with the new dictionary keys, the max value is "d"
|
Thanks @alamb @appletreeisyellow - I should have reviewed the tests more closely - thanks for the feedback. I will make the adjustments now. |
alamb
approved these changes
Jun 30, 2024
findepi
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Jul 16, 2024
…11169) * fix: Support dictionary type in parquet metadata statistics. * Simplify tests. --------- Co-authored-by: Eric Fredine <[email protected]>
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Which issue does this PR close?
Closes #11145.
Rationale for this change
What changes are included in this PR?
Modifies
create_max_min_accsto instantiate accumulators for unpacked data - the value DataType of the Dictionary.This bug is very similar to a previous bug that impacted the Min/Max aggregate functions. #1235
In addition, the
min_max_aggregate_data_typefn is copied fromdatafusion/datafusion/physical-expr/src/aggregate/min_max.rs
Lines 63 to 73 in 8216e32
I'm unsure if copying the function is the right thing to do in order to prevent coupling between the crates or if it should be moved to some core crate? It also seems like the dedicated min and max functions are to be refactored into a user defined functions?
Are these changes tested?
Yes - a new test has been added.
Are there any user-facing changes?
Currently implemented so the column statistics are returned as an unpacked type. So for
DataType::Dictionary(Int32, Utf8)the min or max value is returned asExact(Utf8("a")). Would it be better to return it asExact(Dictionary(Int32, Utf8("a")))? I'm unsure what the previous implementation would have returned and whether or not it was correct. But it's possible that returning it as an unpacked type would be a breaking change if it previously returned it as a Dictionary type.Happy to change the implementation to return a Dictionary type. I'm just unsure which offers the best experience.