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https://issues.apache.org/jira/browse/ARROW-1886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16407178#comment-16407178
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ASF GitHub Bot commented on ARROW-1886:
---------------------------------------
cpcloud commented on a change in pull request #1768: ARROW-1886: [C++/Python]
Flatten struct columns in table
URL: https://github.com/apache/arrow/pull/1768#discussion_r175940858
##########
File path: cpp/src/arrow/table.cc
##########
@@ -127,6 +127,38 @@ std::shared_ptr<ChunkedArray> ChunkedArray::Slice(int64_t
offset) const {
return Slice(offset, length_);
}
+Status ChunkedArray::Flatten(MemoryPool* pool,
+ std::vector<std::shared_ptr<ChunkedArray>>* out)
const {
+ std::vector<std::shared_ptr<ChunkedArray>> flattened;
+ if (type()->id() != Type::STRUCT) {
+ // Emulate non-existent copy constructor
+ flattened.emplace_back(std::make_shared<ChunkedArray>(chunks_));
+ *out = flattened;
+ return Status::OK();
+ }
+ std::vector<ArrayVector> flattened_chunks;
+ for (const auto& chunk : chunks_) {
+ ArrayVector res;
+ RETURN_NOT_OK(dynamic_cast<const StructArray&>(*chunk).Flatten(pool,
&res));
Review comment:
This can be turned into a `static_cast`
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> [Python] Add function to "flatten" structs within tables
> --------------------------------------------------------
>
> Key: ARROW-1886
> URL: https://issues.apache.org/jira/browse/ARROW-1886
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Reporter: Wes McKinney
> Assignee: Antoine Pitrou
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.10.0
>
>
> See discussion in https://issues.apache.org/jira/browse/ARROW-1873
> When a user has a struct column, it may be more efficient to flatten the
> struct into multiple columns of the form {{struct_name.field_name}} for each
> field in the struct. Then when you call {{to_pandas}}, Python dictionaries do
> not have to be created, and the conversion will be much more efficient
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