Mryange opened a new pull request, #65943:
URL: https://github.com/apache/doris/pull/65943
### What problem does this PR solve?
CSV OUTFILE spends substantial CPU time converting FLOAT and DOUBLE values
to strings.
Root cause: the CSV serialization path creates a temporary `std::string` for
every floating-point value, while the formatter generates a fixed number of
significant digits instead of using fmt's faster shortest-roundtrip path.
This change writes formatted values directly to `BufferWritable` and uses
shortest-roundtrip formatting for finite FLOAT and DOUBLE values. In the 1
million row CSV test, the average export time decreased from 14.155 seconds to
8.951 seconds. The focused DOUBLE formatting benchmark improved from 91.656
ns/value to 37.827 ns/value.
### Release note
FLOAT and DOUBLE string serialization now uses the shortest round-trip
representation. NaN and Infinity spelling is unchanged.
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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