#2121 ✓resolved
David Costanzo

JPABase.equals() invokes _key() before checking null/ref equality

Reported by David Costanzo | May 16th, 2017 @ 04:30 PM | in 1.5.0 (closed)

When profiling my application, I noticed an unexpected bottleneck in JPABase.equals(). In my use case, the "this" object and the "other" object arguments are usually references to the same object. However JPABase.equals() calls the relatively expensive _key() method before doing the very fast reference checks, even though it doesn't use the key until after the reference checks.

Per the "Contributor Guide" I am opening a Lighthouse ticket before submitting pull request.

Framework version: 1.4.3
Platform you're using: GNU/Linux

Reproduction steps:
By inspection

In my application's use case, I invoke JPABase.equals() many times with and in most cases the objects are the same reference (it's in a mutator method where, if the field doesn't change, then it's a no-op, otherwise it does an expensive update). Usually equals() operators are written to make this fast. However JPABase.equals() calls _key() before doing any reference checks and _key() uses reflection, which is relatively expensive.

From framework/src/play/db/jpa/JPABase.java

    public boolean equals(Object other) {
        final Object key = this._key(); // <--- expensive calculated here

        if (other == null) {
            return false;
        if (this == other) { // fast reference equality (common case)
            return true;
        if (key == null) { // <-- not used until here
            return false;

JPABase.equals() is functionally correct as-is, but I don't see any reason to call _key() before its return value is needed. Moving the call to _key() below the reference checks will make reference equality fast without slowing down the other cases. This is a non-invasive change that doesn't hurt any use cases and will help some.

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