morningman opened a new pull request, #69568:
URL: https://github.com/apache/doris/pull/69568
### What problem does this PR solve?
Issue Number: None
Related PR: #69567
Problem Summary:
**In short.** A CASE WHEN whose result type is VARBINARY and that has two or
more WHEN branches failed in BE with `argument_type VarBinary not supported`.
BE now selects VARBINARY values the way it selects strings.
**Background.** VARBINARY values reach queries through external tables
(Iceberg, Paimon and Hive binary columns map to VARBINARY) and through
`CAST(... AS VARBINARY)`. BE evaluates CASE WHEN in `VCaseExpr`: it computes,
for every row, the index of the branch that the row takes, and then
`VCaseExpr::_execute_update_result` builds the result column, dispatching on
the result's primitive type to a typed copy loop. Nereids rewrites a CASE with
a single WHEN and an ELSE into `if()`, whose generic path copies values through
`IColumn::insert_from` and accepts any column type.
**The problem, and what it cost.** The dispatch in `_execute_update_result`
had no entry for `TYPE_VARBINARY`, so it fell through to
`NOT_IMPLEMENTED_ERROR`. Every query with such a CASE failed, whatever the
constant-folding mode (the CASE is evaluated by BE, not folded), for example
```sql
SELECT CASE WHEN number % 3 = 0 THEN CAST(concat('a', number) AS VARBINARY)
WHEN number % 3 = 1 THEN CAST('y' AS VARBINARY)
ELSE X'FF' END
FROM numbers("number" = "6");
-- ERROR 1105 (HY000): errCode = 2, detailMessage =
(127.0.0.1)[NOT_IMPLEMENTED_ERROR][E3]
-- argument_type Nullable(VarBinary) not supported
```
Only a CASE with one WHEN and an ELSE worked, because it is evaluated as
`if()`. branch-4.2 has the same gap.
**How this PR fixes it.** `TYPE_VARBINARY` now maps to `ColumnVarbinary`,
and `ColumnVarbinary` takes the per-row copy (`update_result_normal`) that CASE
already uses for strings, both for a nullable result (including CASE without
ELSE, whose unmatched rows are NULL) and for a non-nullable one. FE needs no
change.
**Results.**
| CASE WHEN with a VARBINARY result | Before | After |
|---|---|---|
| Two or more WHEN branches, with ELSE | fails: `argument_type VarBinary not
supported` | returns the selected bytes |
| Two or more WHEN branches, without ELSE | fails: `argument_type
Nullable(VarBinary) not supported` | returns the selected bytes, NULL for
unmatched rows |
| One WHEN with ELSE (rewritten to `if()`) | works | works (unchanged) |
- BE unit tests: `VCaseVarbinaryTest` adds two cases through
`_execute_update_result`: a non-nullable result with ELSE (a column branch, a
constant branch, NUL and non-UTF-8 bytes) and a nullable result without ELSE
(NULL from a branch and from unmatched rows). Both fail without the change with
the error above. `VCaseSelectionTest` still passes (50 cases in total).
- Regression test:
`query_p0/sql_functions/binary_functions/test_varbinary_case_when` runs CASE
with and without ELSE over a table, over `numbers()` and on constants, in the
three constant-folding modes (FE folding, folding by BE, no folding); the
results match in all modes.
### Release note
Fix: a CASE WHEN with two or more WHEN branches and a VARBINARY result
failed with "argument_type VarBinary not supported".
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [x] Regression test
- [x] 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:
- [x] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [x] 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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