xanderbailey opened a new pull request, #19737:
URL: https://github.com/apache/datafusion/pull/19737
## Problem
The ascii function previously collected all output values into an
intermediate
Vec<i32> before constructing the final Int32Array. This approach caused an
unnecessary heap allocation that scaled with the size of the input array.
## Solution
Replace the collect-based approach with direct use of Int32Array::builder,
which constructs the array incrementally without intermediate storage.
## Which issue does this PR close?
<!--
We generally require a GitHub issue to be filed for all bug fixes and
enhancements and this helps us generate change logs for our releases. You can
link an issue to this PR using the GitHub syntax. For example `Closes #123`
indicates that this PR will close issue #123.
-->
- Closes #.
## Rationale for this change
- Eliminates one heap allocation per function call
- Reduces memory pressure for large arrays
- Follows the same pattern used by other optimized string functions in the
codebase
- Maintains identical functionality with all existing tests passing
The optimization removes an O(n) memory allocation where n is the array
length.
While the performance improvement may be modest for small arrays, it becomes
more significant for larger datasets and reduces GC pressure in
memory-constrained
environments.
<!--
Why are you proposing this change? If this is already explained clearly in
the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand your
changes and offer better suggestions for fixes.
-->
## What changes are included in this PR?
### Before
```rust
let values: Vec<_> = (0..array.len())
.map(|i| { /* compute ascii value */ })
.collect();
let array = Int32Array::new(values.into(), array.nulls().cloned());
```
### After
```rust
let mut builder = Int32Array::builder(len);
for i in 0..len {
if array.is_null(i) {
builder.append_null();
} else {
let value = /* compute ascii value */;
builder.append_value(value);
}
}
```
<!--
There is no need to duplicate the description in the issue here but it is
sometimes worth providing a summary of the individual changes in this PR.
-->
## Are these changes tested?
<!--
We typically require tests for all PRs in order to:
1. Prevent the code from being accidentally broken by subsequent changes
2. Serve as another way to document the expected behavior of the code
If tests are not included in your PR, please explain why (for example, are
they covered by existing tests)?
-->
## Are there any user-facing changes?
<!--
If there are user-facing changes then we may require documentation to be
updated before approving the PR.
-->
<!--
If there are any breaking changes to public APIs, please add the `api
change` label.
-->
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
