HappenLee opened a new pull request, #63498:
URL: https://github.com/apache/doris/pull/63498
### What problem does this PR solve?
Issue Number: N/A
Problem Summary:
`SELECT length(col_varchar)` on a low-cardinality (dict-encoded) column
failed with:
NOT_IMPLEMENTED_ERROR: Method insert_offsets_from_lengths is not supported
Root cause (two-step):
1. When `enable_low_cardinality_optimize=true`, the predicate column is
created as `ColumnDictI32` by `Schema::get_predicate_column_ptr()`. The
`only_read_offsets` code path in `BinaryDictPageDecoder` resolves dict codes to
lengths and calls `dst->insert_offsets_from_lengths()`, but `ColumnDictI32`
does not implement that method.
2. After converting `ColumnDictI32` to `PredicateColumnType<TYPE_STRING>`
via `convert_to_predicate_column_if_dictionary()`, the same call failed again
because `PredicateColumnType` also lacked the implementation.
Fix:
- `binary_dict_page.cpp`: call `convert_to_predicate_column_if_dictionary()`
on `dst` before invoking `insert_offsets_from_lengths` in both `next_batch()`
and `read_by_rowids()` (covers dict-encoded pages and the plain-encoded
fallback path).
- `predicate_column.h`: implement `insert_offsets_from_lengths` for the
`StringRef` specialisation of `PredicateColumnType`. A single backing buffer
is allocated from the internal Arena and zero-filled; each element records the
correct length so that downstream `filter_by_selector` /
`copy_column_data_by_selector` can materialise the right-sized strings into the
output `ColumnString`, giving the correct result for `length()`.
### Release note
Fix crash/error when calling `length()` on a varchar/char column that uses
the low-cardinality (dictionary) optimisation.
### Check List (For Author)
- Test: Manual test (query reproduced and confirmed fixed)
- Behavior changed: No
- Does this need documentation: No
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
### Release note
None
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] 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:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] 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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