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https://issues.apache.org/jira/browse/ARROW-1886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16407174#comment-16407174
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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_r175944515
##########
File path: cpp/src/arrow/util/bit-util.cc
##########
@@ -172,4 +172,58 @@ bool BitmapEquals(const uint8_t* left, int64_t
left_offset, const uint8_t* right
return true;
}
+namespace {
+
+void AlignedBitmapAnd(const uint8_t* left, int64_t left_offset, const uint8_t*
right,
+ int64_t right_offset, uint8_t* out, int64_t out_offset,
+ int64_t length) {
+ DCHECK_EQ(left_offset % 8, right_offset % 8);
+ DCHECK_EQ(left_offset % 8, out_offset % 8);
+
+ const int64_t nbytes = BitUtil::BytesForBits(length + left_offset);
+ left += left_offset / 8;
+ right += right_offset / 8;
+ out += out_offset / 8;
+ for (int64_t i = 0; i < nbytes; ++i) {
+ out[i] = left[i] & right[i];
+ }
+}
+
+void UnalignedBitmapAnd(const uint8_t* left, int64_t left_offset, const
uint8_t* right,
+ int64_t right_offset, uint8_t* out, int64_t out_offset,
+ int64_t length) {
+ auto left_reader = internal::BitmapReader(left, left_offset, length);
+ auto right_reader = internal::BitmapReader(right, right_offset, length);
+ auto writer = internal::BitmapWriter(out, out_offset, length);
+ for (int64_t i = 0; i < length; ++i) {
+ if (left_reader.IsSet() && right_reader.IsSet()) {
+ writer.Set();
+ }
+ left_reader.Next();
+ right_reader.Next();
+ writer.Next();
+ }
+ writer.Finish();
+}
+
+} // namespace
+
+Status BitmapAnd(MemoryPool* pool, const uint8_t* left, int64_t left_offset,
+ const uint8_t* right, int64_t right_offset, int64_t length,
+ int64_t out_offset, std::shared_ptr<Buffer>* out_buffer) {
Review comment:
I guess there's some precedent here for that, but calling this `BitmapAnd`
and having it take `MemoryPool` as its first argument is confusing.
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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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