**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
data,
                        oc.evaluatorToString,
                        oc.expectedType,
                        nullValue(),
                        null,
                        oc.getExpectedTypeError()
                    );
                }));
                if (firstTimeSeenSignature) {
                    List<DataType> typesWithNull = IntStream.range(0, original.types().size())
                        .mapToObj(i -> i == finalNullPosition ? DataTypes.NULL : original.types().get(i))
                        .toList();
                    boolean newSignature = uniqueSignatures.add(typesWithNull);
                    if (newSignature) {
                        suppliers.add(new TestCaseSupplier(typesWithNull, () -> {
                            TestCaseSupplier.TestCase oc = original.get();
                            List<TestCaseSupplier.TypedData> data = IntStream.range(0, oc.getData().size()).mapToObj(i -> {
                                TestCaseSupplier.TypedData od = oc.getData().get(i);
                                if (i == finalNullPosition) {
                                    return new TestCaseSupplier.TypedData(null, DataTypes.NULL, od.name());
                                }
                                return od;
                            }).toList();
                            return new TestCaseSupplier.TestCase(
                                data,
                                "LiteralsEvaluator[lit=null]",
                                entirelyNullPreservesType == false && oc.getData().size() == 1 ? DataTypes.NULL : oc.expectedType,
                                nullValue(),
                                null,
                                oc.getExpectedTypeError()