comphead commented on code in PR #5348: URL: https://github.com/apache/datafusion-comet/pull/5348#discussion_r3778885329
########## docs/source/contributor-guide/expression-audits/string_funcs.md: ########## @@ -245,6 +245,10 @@ - Spark 3.5.8 (audited 2026-05-27): registry alias of `Upper`. Same support as `upper`. - Spark 4.0.1 (audited 2026-05-27): unchanged alias of `Upper`. +## unbase64 + +- Native candidate (assessed 2026-08-13): Recommended ([#5347](https://github.com/apache/datafusion-comet/issues/5347)). Compatibility: High (semantics identical across 3.4.3, 3.5.8, 4.0.1, and 4.1.1; no collation, timezone, locale, or decimal dependence; the `java.util.Base64.getMimeDecoder()` skip rule and its four `IllegalArgumentException` conditions are fully enumerable from the JDK source, and Comet already ports the mirror-image MIME encoder in `spark_base64`). Upside: High (5 JVM heap allocations per non-null row, roughly 41k per 8192-row batch, plus a double scan from the MIME `decodedOutLength` pre-scan, all removable with the `spark_unhex` pattern of a 256-entry table plus a preallocated `BinaryBuilder`; counts derived from source, not measured, and workload presence is unmeasured). Upstream `datafusion-spark::SparkUnBase64` is not usable: it lowers to `decode(bin, 'base64pad')`, whose strict engine errors on the non-alphabet bytes Spark skips, so it cannot round-trip Com et's own CRLF-chunked `base64` output. Review Comment: is it part of PR? -- 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]
