**Build scan:**
https://gradle-enterprise.elastic.co/s/fvg2knbi424p4/tests/:x-pack:plugin:esql:test/org.elasticsearch.xpack.esql.expression.function.scalar.conditional.LeastTests/testEvaluateInManyThreads%20%7BTestCase=(%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E)%20null%20in%204%7D
**Reproduction lines:**
```
gradlew ':x-pack:plugin:esql:test' --tests "org.elasticsearch.xpack.esql.expression.function.scalar.conditional.GreatestTests.testEvaluateInManyThreads {TestCase=(<mv_integer>) null in 0}" -Dtests.seed=BCCD8A2AFCEA37CB -Dtests.locale=zh -Dtests.timezone=Europe/Guernsey -Druntime.java=21

gradlew ':x-pack:plugin:esql:test' --tests "org.elasticsearch.xpack.esql.expression.function.scalar.conditional.LeastTests.testEvaluateInManyThreads {TestCase=(<keyword>, <keyword>, <keyword>, <keyword>, <keyword>, <keyword>, <keyword>) null in 4}" -Dtests.seed=BCCD8A2AFCEA37CB -Dtests.locale=lt -Dtests.timezone=Indian/Christmas -Druntime.java=21

 gradlew ':x-pack:plugin:esql:test' --tests "org.elasticsearch.xpack.esql.expression.function.scalar.conditional.GreatestTests.testEvaluateInManyThreads {TestCase=(<mv_integer>) null in 0}" -Dtests.seed=BCCD8A2AFCEA37CB -Dtests.locale=zh -Dtests.timezone=Europe/Guernsey -Druntime.java=21
```

**Applicable branches:**
main

**Reproduces locally?:**
Yes

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.esql.expression.function.scalar.conditional.LeastTests&tests.test=testEvaluateInManyThreads%20%7BTestCase%3D(%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E,%20%3Ckeyword%3E)%20null%20in%204%7D


**Failure excerpt:**
```
org.elasticsearch.xpack.esql.expression.function.scalar.conditional.GreatestTests > classMethod FAILED
    java.lang.AssertionError: expected:<[boolean, double, integer, ip, keyword, long, text, version]> but was:<[integer]>


```
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/function/AbstractFunctionTestCase.java
}
            for (Future<?> f : futures) {
                f.get();
            }
        } finally {
            exec.shutdown();
        }
    }
    public final void testEvaluatorToString() {
        assumeTrue("nothing to do if a type error", testCase.getExpectedTypeError() == null);
        assumeTrue("All test data types must be representable in order to build fields", testCase.allTypesAreRepresentable());
        var factory = evaluator(buildFieldExpression(testCase));
        try (ExpressionEvaluator ev = factory.get(driverContext())) {
            assertThat(ev.toString(), equalTo(testCase.evaluatorToString));
        }
    }
    public final void testFactoryToString() {
        assumeTrue("nothing to do if a type error", testCase.getExpectedTypeError() == null);
        assumeTrue("All test data types must be representable in order to build fields", testCase.allTypesAreRepresentable());
        var factory = evaluator(buildFieldExpression(testCase));
        assertThat(factory.toString(), equalTo(testCase.evaluatorToString));
    }
    public final void testFold() {
        Expression expression = buildLiteralExpression(testCase);
        if (testCase.getExpectedTypeError() != null) {
            assertTrue(expression.typeResolved().unresolved());
            assertThat(expression.typeResolved().message(), equalTo(testCase.getExpectedTypeError()));
            return;
        }
        assertFalse(expression.typeResolved().unresolved());