ding-young opened a new pull request, #17315: URL: https://github.com/apache/datafusion/pull/17315
## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123. --> ## Rationale for this change When we spill `RecordBatch` on external sorting, we call `batch.get_sliced_size` to report `max_record_batch_size` in each spill file. Thereby we can safely read the batch back from spill file with correct memory estimation. However, it is found (in https://github.com/apache/datafusion/pull/17029) that `get_sliced_size` underestimated the memory size for `StringViewArray`. The diff was quite large i.e. when correct batch size was 1392730 bytes, it returned 163840 bytes, which means the actual memory usage may far exceed the configured memory_limit, especially when merging spill file. This underestimation happens because arrow api `get_slice_memory_size` counts for only `views` buffer for `StringViewArray` while ignoring the capacity for `data` (payload) buffer. See https://github.com/apache/arrow-rs/blob/a620957bc98b7aa14faec10635bb798932f00bf9/arrow-data/src/data.rs#L464-L476 https://github.com/apache/arrow-rs/blob/a620957bc98b7aa14faec10635bb798932f00bf9/arrow-data/src/data.rs#L1743-L1752 <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> ## What changes are included in this PR? This PR corrects the memory estimation for `batch.get_sliced_size` for `StringViewArray` by manually adding up the capacity for data buffers. Since we call this function after `StringViewArray.gc`, it is safe to add the buffer capacity directly. We may need to upstream this patch if needed. <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> ## Are these changes tested? Yes. <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> ## Are there any user-facing changes? Some external sort queries (including those that use `StringViewArray`) may fail more frequently under tight memory limits, because we fix the underestimation. However, since this reflects actual memory usage and we're still working on the fix, so I think it's okay to proceed. <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. --> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
