winfriedgerlach opened a new pull request, #22641:
URL: https://github.com/apache/kafka/pull/22641
I propose a small optimization for the `RecordHeaders(Header[])`
constructor. Since this code is used on the hot-path for `Consumer.poll()` (via
`Fetcher` --> `FetchCollector` --> `CompletedFetch`), I think this code should
not be wasteful.
Have a look at the original code:
```java
public RecordHeaders(Header[] headers) {
this(headers == null ? null : Arrays.asList(headers)); // (1)
}
public RecordHeaders(Iterable<Header> headers) {
//Use efficient copy constructor if possible, fallback to iteration
otherwise
if (headers == null) {
this.headers = new ArrayList<>();
} else if (headers instanceof RecordHeaders) {
this.headers = new ArrayList<>(((RecordHeaders)
headers).headers);
} else {
this.headers = new ArrayList<>(); // (2)
for (Header header : headers) { // (3)
Objects.requireNonNull(header, "Header cannot be null.");
this.headers.add(header);
}
}
}
```
Note:
* If `RecordHeaders(Headers[])` is called with a **zero-length** array,
`Arrays.asList()` at (1) creates an `ArrayList` which is then never used, since
the `ArrayList` created at (2) will be the result (and the for-each loop will
never be entered).
* If `RecordHeaders(Headers[])` is called with a **non-zero-length** array,
the list created with `Arrays.asList()` at (1) is also just a useless wrapper.
* The for-each-loop at (3) is also wasteful in the `Array` use-case, since
it creates a new `Iterator` via `ArrayList.iterator()`, while a for-each-loop
over an array does not construct an object (cf. [JLS
14.14.2](https://docs.oracle.com/javase/specs/jls/se25/html/jls-14.html#jls-14.14.2)).
Thus I propose a simple change that avoids both object creations: the
`ArrayList` that's merely used "as transport" to the other constructor and the
`Iterator` that's not needed for iterating an `Array`.
--
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]
