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[SPARK-48281][SQL] Alter string search logic for UTF8_BINARY_LCASE collation (StringInStr, SubstringIndex) #46589

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@uros-db uros-db commented May 15, 2024

What changes were proposed in this pull request?

String searching in UTF8_BINARY_LCASE now works on character-level, rather than on byte-level. For example: instr("İ", "i"); now returns 0, because there exists no start, len such that lowercase(substring("İ", start, len)) == "i".

Why are the changes needed?

Fix functions that give unusable results due to one-to-many case mapping when performing string search under UTF8_BINARY_LCASE (see example above).

Does this PR introduce any user-facing change?

Yes, behaviour of instr and substring_index expressions is changed for edge cases with one-to-many case mapping.

How was this patch tested?

New unit tests in CollationSupportSuite.

Was this patch authored or co-authored using generative AI tooling?

No.

@github-actions github-actions bot added the SQL label May 15, 2024
@uros-db uros-db changed the title [WIP][SPARK-48281][SQL] Alter string search logic for UTF8_BINARY_LCASE collation (StringInStr, SubStringIndex) [WIP][SPARK-48281][SQL] Alter string search logic for UTF8_BINARY_LCASE collation (StringInStr, SubstringIndex) May 15, 2024
@uros-db uros-db requested a review from mkaravel May 17, 2024 08:25
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Thank you for addressing my comments.
LGTM!

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Please update the PR description.

@uros-db uros-db changed the title [WIP][SPARK-48281][SQL] Alter string search logic for UTF8_BINARY_LCASE collation (StringInStr, SubstringIndex) [SPARK-48281][SQL] Alter string search logic for UTF8_BINARY_LCASE collation (StringInStr, SubstringIndex) May 21, 2024
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updated PR description & title
@cloud-fan ready for review

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@uros-db Please see my comment about the PR description in #46511
The same comment applies to the PR description for this PR.

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please fix merge conflicts.

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thanks, merging to master!

@cloud-fan cloud-fan closed this in 0461745 May 29, 2024
riyaverm-db pushed a commit to riyaverm-db/spark that referenced this pull request Jun 7, 2024
…llation (StringInStr, SubstringIndex)

### What changes were proposed in this pull request?
String searching in UTF8_BINARY_LCASE now works on character-level, rather than on byte-level. For example: `instr("İ", "i")`; now returns 0, because there exists no `start, len` such that `lowercase(substring("İ", start, len)) == "i"`.

### Why are the changes needed?
Fix functions that give unusable results due to one-to-many case mapping when performing string search under UTF8_BINARY_LCASE (see example above).

### Does this PR introduce _any_ user-facing change?
Yes, behaviour of `instr` and `substring_index` expressions is changed for edge cases with one-to-many case mapping.

### How was this patch tested?
New unit tests in `CollationSupportSuite`.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes apache#46589 from uros-db/alter-lcase-vol2.

Authored-by: Uros Bojanic <157381213+uros-db@users.noreply.github.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
cloud-fan pushed a commit that referenced this pull request Jun 11, 2024
### 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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