[
https://issues.apache.org/jira/browse/ARROW-2351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16420087#comment-16420087
]
ASF GitHub Bot commented on ARROW-2351:
---------------------------------------
gaolizhou commented on a change in pull request #1803: ARROW-2351 [C++]
StringBuilder::append(vector<string>...) not impleme…
URL: https://github.com/apache/arrow/pull/1803#discussion_r178223472
##########
File path: cpp/src/arrow/builder.cc
##########
@@ -1385,6 +1385,28 @@ const uint8_t* BinaryBuilder::GetValue(int64_t i,
int32_t* out_length) const {
StringBuilder::StringBuilder(MemoryPool* pool) : BinaryBuilder(utf8(), pool) {}
+Status StringBuilder::Append(const std::vector<std::string>& values,
+ uint8_t* null_bytes) {
+ std::size_t total_length = std::accumulate(
+ values.begin(), values.end(), 0ULL,
+ [](uint64_t sum, const std::string& str) { return sum + str.size(); });
Review comment:
Tested with below code, for-loop-solution and accumulate-solution almost has
same performance.To count 100000000 strings, for-loop-solution takes 21.2312 ms,
accumulate-solution takes 21.5120 ms.
log:
```
lizgao@lizgao-ubuntu:~/CLionProjects/cmake-test$ ./cmake_test
WARNING: Logging before InitGoogleLogging() is written to STDERR
I0330 10:29:56.864248 3989 accmulate-lambda-performance.cc:15] Begin
for_loop_solution
I0330 10:29:57.076560 3989 accmulate-lambda-performance.cc:19] End
for_loop_solution = 8000000000
I0330 10:29:57.076603 3989 accmulate-lambda-performance.cc:23] Begin
accumulate_solution
I0330 10:29:57.291723 3989 accmulate-lambda-performance.cc:27] End
accumulate_solution = 8000000000
```
```
//
// Created by lizgao on 3/30/18.
//
#include <cstdint>
#include <numeric>
#include <string>
#include <vector>
#include <glog/logging.h>
namespace {
void for_loop_solution(const std::vector<std::string> &values) {
std::size_t total_length = 0;
std::size_t cnt = values.size();
LOG(INFO) << "Begin for_loop_solution";
for (std::size_t i = 0; i < cnt; ++i) {
total_length += values[i].size();
}
LOG(INFO) << "End for_loop_solution = " << total_length;
}
void accumulate_solution(const std::vector<std::string> &values) {
LOG(INFO) << "Begin accumulate_solution";
std::size_t total_length = std::accumulate(
values.begin(), values.end(), 0ULL,
[](uint64_t sum, const std::string& str) { return sum + str.size();
});
LOG(INFO) << "End accumulate_solution = " << total_length;
}
}
void accumulate_lambda_performance_test() {
std::vector<std::string> str_list(100000000, std::string(80, '*'));
for_loop_solution(str_list);
accumulate_solution(str_list);
}
```
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> [C++] StringBuilder::append(vector<string>...) not implemented
> --------------------------------------------------------------
>
> Key: ARROW-2351
> URL: https://issues.apache.org/jira/browse/ARROW-2351
> Project: Apache Arrow
> Issue Type: Bug
> Components: C++
> Affects Versions: 0.9.0
> Reporter: Rares Vernica
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.10.0
>
>
> For {{StringBuilder}} an {{append(vector<string>, uint8_t*)}} function is
> [declared|https://github.com/apache/arrow/blob/7b2c79765cf92760e1f8cca079159d9613b86412/cpp/src/arrow/builder.h#L721]
> and
> [documented|http://arrow.apache.org/docs/cpp/classarrow_1_1_string_builder.html#a59be34b5e11017a392b4ee019d90da3c]
> but it does not seem to be implemented.
> {code:java}
> undefined reference to `arrow::StringBuilder::Append(std::vector<std::string,
> std::allocator<std::string> > const&, unsigned char*)'
> collect2: error: ld returned 1 exit status
> {code}
> Also worth noting is that the similar function in {{NumericBuilder}} uses
> {{vector<bool>}} for the null values instead of {{uint8_t*}}. It might be
> worth making them consistent.
>
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