[SPARK-48283][SQL] Modify string comparison for UTF8_BINARY_LCASE #46700
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common/unsafe/src/main/java/org/apache/spark/sql/catalyst/util/CollationAwareUTF8String.java
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common/unsafe/src/test/java/org/apache/spark/unsafe/types/CollationSupportSuite.java
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Main question here is whether we want to fix the "conversion" from UTF8String to Java string in this PR or in a follow up PR (see comments in the PR). Either way is fine with me. By "conversion" here I mean:
- Splitting the UTF8String value into illegal and legal UTF8 byte sequences as per UNICODE (no surrogate semantics).
- Replacing illegal byte sequences with U+FFFD.
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mkaravel
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Jun 6, 2024
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in conclusion: we'll need to modify the logic for illegal UTF8 byte sequence replacement, to stay consistent with ICU4C however, we'll do this in a follow-up PR |
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@cloud-fan please review |
cloud-fan
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Jun 6, 2024
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thanks, merging to master! |
This was referenced Jun 10, 2024
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### What changes were proposed in this pull request? Renaming `UTF8_BINARY_LCASE` collation to `UTF8_LCASE`. ### Why are the changes needed? As part of the collation effort in Spark, we've moved away from byte-by-byte logic towards character-by-character logic, so what we used to call `UTF8_BINARY_LCASE` is now more precisely `UTF8_LCASE`. For example, string searching in UTF8_LCASE now works on character-level (rather than on byte-level), which is reflected in this PRs: #46511, #46589, #46682, #46761, #46762. In addition, string comparison also works on character-level now, as per the changes introduced in this PR: #46700. ### Does this PR introduce _any_ user-facing change? Yes, what was previously named `UTF8_BINARY_LCASE` collation, will from now on be named `UTF8_LCASE`. ### How was this patch tested? Existing tests. ### Was this patch authored or co-authored using generative AI tooling? No. Closes #46924 from uros-db/rename-lcase. Authored-by: Uros Bojanic <157381213+uros-db@users.noreply.github.com> Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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What changes were proposed in this pull request?
String comparison and hashing in UTF8_BINARY_LCASE is now context-unaware, and uses ICU root locale rules to convert string to lowercase at code point level, taking into consideration special cases for one-to-many case mapping. For example: comparing "ΘΑΛΑΣΣΙΝΟΣ" and "θαλασσινοσ" under UTF8_BINARY_LCASE now returns true, because Greek final sigma is special-cased in the new comparison implementation.
Why are the changes needed?
Does this PR introduce any user-facing change?
Yes, comparing strings under UTF8_BINARY_LCASE will now give different results in two kinds of special cases (Turkish dotted letter "i" and Greek final letter "sigma").
How was this patch tested?
Unit tests in
CollationSupportSuite.Was this patch authored or co-authored using generative AI tooling?
No.