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Posted to reviews@spark.apache.org by "landlord-matt (via GitHub)" <gi...@apache.org> on 2023/11/17 15:54:49 UTC
[PR] [MINOR][Docs] Clarify sort behaviour for structs [spark]
landlord-matt opened a new pull request, #43871:
URL: https://github.com/apache/spark/pull/43871
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It clarifies what the the natural order of a struct is. This is to my knowledge never stated anywhere, but according to this [Stack Overflow answer](https://stackoverflow.com/a/68848379) it is the first field.
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It was unclear how this would behave for structs.
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It improves the documentation
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Not applicable
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No
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "landlord-matt (via GitHub)" <gi...@apache.org>.
landlord-matt commented on code in PR #43871:
URL: https://github.com/apache/spark/pull/43871#discussion_r1399028056
##########
python/pyspark/sql/functions.py:
##########
@@ -14102,7 +14102,7 @@ def sort_array(col: "ColumnOrName", asc: bool = True) -> Column:
Collection function: sorts the input array in ascending or descending order according
to the natural ordering of the array elements. Null elements will be placed at the beginning
of the returned array in ascending order or at the end of the returned array in descending
- order.
+ order. The natural order of a struct is the natural order of the first field in the struct schema.
Review Comment:
Maybe you are right and StackOverflow is wrong. I'm not so good at Scala, but I think it is decided [here ](https://github.com/apache/spark/blob/398bff77b1c837aed55f4f10ff1157f7da813570/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateOrdering.scala#L58) or perhaps [here](https://github.com/apache/spark/blob/398bff77b1c837aed55f4f10ff1157f7da813570/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/PhysicalDataType.scala#L318)
Maybe it is sorting first on the first field, then on second and so on.
A more correct description would in this case be
```suggestion
order. The natural order of a struct is the natural order of the underlying fields of the struct schema in positional order.
```
I'm not 100 % sure this is true either. Are we sure that we get the field in positional order when it iterates through the fields?
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "landlord-matt (via GitHub)" <gi...@apache.org>.
landlord-matt commented on PR #43871:
URL: https://github.com/apache/spark/pull/43871#issuecomment-1824563107
@JoshRosen : Thanks for clarifying! While it is true that the code is available for anyone to read and it is well written, I still think it would nice to have a text version for us dummies. Instead of explaining it in the function, I also had this brilliant idea of explaining it in the data type document. What do you think of this proposal? https://github.com/apache/spark/pull/43981
Also, I am still wondering about this section. It loops through all the fields in the schema and adds it to that magic ordering array. I assume that ordering array corresponds to "ORDER BY 1,2,3", but what is "1,2,3" in this case? How does it iterate through the schema?
https://github.com/apache/spark/blob/fdcd20f4b51c3ddddaae12f7d3f429e7b77c9f5e/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/PhysicalDataType.scala#L318-L329
If you want you can also check out my other proposal about collect_list that was ignored :( https://github.com/apache/spark/pull/43787
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "HyukjinKwon (via GitHub)" <gi...@apache.org>.
HyukjinKwon commented on code in PR #43871:
URL: https://github.com/apache/spark/pull/43871#discussion_r1398565942
##########
python/pyspark/sql/functions.py:
##########
@@ -14102,7 +14102,7 @@ def sort_array(col: "ColumnOrName", asc: bool = True) -> Column:
Collection function: sorts the input array in ascending or descending order according
to the natural ordering of the array elements. Null elements will be placed at the beginning
of the returned array in ascending order or at the end of the returned array in descending
- order.
+ order. The natural order of a struct is the natural order of the first field in the struct schema.
Review Comment:
Oh, so it doesn't sort by the second field?
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] closed pull request #43871: [MINOR][DOCS] Clarify sort behaviour for structs
URL: https://github.com/apache/spark/pull/43871
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "landlord-matt (via GitHub)" <gi...@apache.org>.
landlord-matt commented on PR #43871:
URL: https://github.com/apache/spark/pull/43871#issuecomment-1820696947
Another alternative would be instead of writing it for this function, we could add something on this documentation page. I don't it is open source though https://spark.apache.org/docs/latest/sql-ref-datatypes.html
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "JoshRosen (via GitHub)" <gi...@apache.org>.
JoshRosen commented on PR #43871:
URL: https://github.com/apache/spark/pull/43871#issuecomment-1821456888
> I don't think this documentation is open source though, so I can't submit a proposal.
The Spark website's source code can be found at https://github.com/apache/spark-website
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Re: [PR] [MINOR][DOCS] Clarify sort behaviour for structs [spark]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #43871:
URL: https://github.com/apache/spark/pull/43871#issuecomment-1974952321
We're closing this PR because it hasn't been updated in a while. This isn't a judgement on the merit of the PR in any way. It's just a way of keeping the PR queue manageable.
If you'd like to revive this PR, please reopen it and ask a committer to remove the Stale tag!
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