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https://issues.apache.org/jira/browse/ARROW-1886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16407175#comment-16407175
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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_r175943904
##########
File path: cpp/src/arrow/util/bit-util-test.cc
##########
@@ -41,6 +44,59 @@ static void EnsureCpuInfoInitialized() {
}
}
+void WriteVectorToWriter(internal::BitmapWriter& writer, const
std::vector<int> values) {
+ for (const auto& value : values) {
+ if (value) {
+ writer.Set();
+ } else {
+ writer.Clear();
+ }
+ writer.Next();
+ }
+ writer.Finish();
+}
+
+void BitmapFromVector(const std::vector<int>& values, int64_t bit_offset,
+ std::shared_ptr<Buffer>* out_buffer, int64_t*
out_length) {
+ const int64_t length = values.size();
+ *out_length = length;
+ ASSERT_OK(GetEmptyBitmap(default_memory_pool(), length + bit_offset,
out_buffer));
+ auto writer = internal::BitmapWriter((*out_buffer)->mutable_data(),
bit_offset, length);
+ WriteVectorToWriter(writer, values);
+}
+
+#define ASSERT_READER_SET(reader) \
+ do { \
+ ASSERT_TRUE(reader.IsSet()); \
+ ASSERT_FALSE(reader.IsNotSet()); \
+ reader.Next(); \
+ } while (0)
+
+#define ASSERT_READER_NOT_SET(reader) \
+ do { \
+ ASSERT_FALSE(reader.IsSet()); \
+ ASSERT_TRUE(reader.IsNotSet()); \
+ reader.Next(); \
+ } while (0)
+
+// Assert that a BitmapReader yields the given bit values
+void ASSERT_READER_VALUES(internal::BitmapReader& reader, std::vector<int>
values) {
+ for (const auto& value : values) {
+ if (value) {
+ ASSERT_READER_SET(reader);
+ } else {
+ ASSERT_READER_NOT_SET(reader);
+ }
+ }
+}
+
+// Assert equal contents of a memory area and a vector of bytes
+void ASSERT_BYTES_EQ(const uint8_t* left, const std::vector<uint8_t>& right) {
+ // No direct conversion from (T*, size) to vector<T>
Review comment:
Can't you construct it like this?
```c++
std::vector<T> left_array(left, left + right.size());
```
Or am I missing something
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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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