shahwazreza opened a new pull request, #26957:
URL: https://github.com/apache/datafusion/pull/26957
## Which issue does this PR close?
- Closes #26948.
## Rationale for this change
`repeat` on a `LargeUtf8` string with a huge count, such as
`repeat(arrow_cast('a', 'LargeUtf8'), 1152921504606846976)`, aborts the process
or panics instead of returning an error. `Utf8` and `Utf8View` already return
an error above `i32::MAX` bytes, but the `LargeUtf8` cap was `i64::MAX`, which
admits sizes no allocation can satisfy.
## What changes are included in this PR?
The issue asks whether to use a fixed cap or fallible allocation. This PR
uses a fixed cap, `LARGE_UTF8_MAX_SIZE = u32::MAX`, in both the scalar and the
array paths. I chose it over fallible allocation for two reasons:
- The array path allocates through
`GenericStringArrayBuilder::with_capacity`, which has no fallible variant.
Making it fallible seems to belong to #22688 rather than this fix.
- A cap gives the same error behavior as `Utf8`, and it matches DuckDB's
string size limit, which the issue mentions.
The exact cap value is a judgment call. I picked `u32::MAX` so `LargeUtf8`
still allows larger results than `Utf8`. I'm happy to change it, for example to
PostgreSQL's 1 GB, if reviewers prefer.
As the issue notes, this does not guard against an allocation under the cap
that succeeds under overcommit and fails later.
## What is the testing strategy for this PR?
Two unit tests in `repeat.rs` use a count of `1 << 60` with `LargeUtf8`. One
covers the scalar path through `test_function!`, and one covers the array path.
Both previously aborted the test process. Now they get the overflow error.
## Are there any user-facing changes?
`repeat` now returns an error for `LargeUtf8` results larger than `u32::MAX`
bytes instead of attempting them.
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