**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
public final void testEvaluate() {
        testEvaluate(false);
    }
    public final void testEvaluateFloating() {
        testEvaluate(true);
    }
    private void testEvaluate(boolean readFloating) {
        assumeTrue("All test data types must be representable in order to build fields", testCase.allTypesAreRepresentable());
        logger.info(
            "Test Values: " + testCase.getData().stream().map(TestCaseSupplier.TypedData::toString).collect(Collectors.joining(","))
        );
        Expression expression = readFloating ? buildDeepCopyOfFieldExpression(testCase) : buildFieldExpression(testCase);
        if (testCase.getExpectedTypeError() != null) {
            assertTrue("expected unresolved", expression.typeResolved().unresolved());
            if (readFloating == false) {
                
                assertThat(expression.typeResolved().message(), equalTo(testCase.getExpectedTypeError()));
            }
            return;
        }
        assertFalse("expected resolved", expression.typeResolved().unresolved());
        expression = new FoldNull().rule(expression);
        assertThat(expression.dataType(), equalTo(testCase.expectedType));
        
        Object result;
        try (ExpressionEvaluator evaluator = evaluator(expression).get(driverContext())) {
            try (Block.Ref ref = evaluator.eval(row(testCase.getDataValues()))) {
                result = toJavaObject(ref.block(), 0);
            }
        }