```
from employees | keep * | mv_expand first_name
```

throws UnresolvedException:

```
org.elasticsearch.xpack.ql.capabilities.UnresolvedException: Invalid call to attribute on an unresolved object ?*
        at org.elasticsearch.xpack.ql.expression.UnresolvedNamedExpression.toAttribute(UnresolvedNamedExpression.java:44)
        at org.elasticsearch.xpack.ql.expression.Expressions.asAttributes(Expressions.java:40)
        at org.elasticsearch.xpack.ql.plan.logical.Project.output(Project.java:62)
        at org.elasticsearch.xpack.esql.plan.logical.MvExpand.<init>(MvExpand.java:31)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.lambda$visitMvExpandCommand$3(LogicalPlanBuilder.java:154)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:89)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitCompositeQuery(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$CompositeQueryContext.accept(EsqlBaseParser.java:232)
        at org.elasticsearch.xpack.ql.parser.ParserUtils.typedParsing(ParserUtils.java:51)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.plan(LogicalPlanBuilder.java:73)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:82)
        at org.elasticsearch.xpack.esql.parser.LogicalPlanBuilder.visitSingleStatement(LogicalPlanBuilder.java:66)
        at org.elasticsearch.xpack.esql.parser.EsqlBaseParser$SingleStatementContext.accept(EsqlBaseParser.java:169)
```

The problem is that MV_EXPAND tries to pre-calculate the output too early, when the resolution did not happen yet.
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java
);
    }
    public void testIdentifiersAsIndexPattern() {
        assertIdentifierAsIndexPattern("foo", "from `foo`");
        assertIdentifierAsIndexPattern("foo,test-*", "from `foo`,`test-*`");
        assertIdentifierAsIndexPattern("foo,test-*", "from foo,test-*");
        assertIdentifierAsIndexPattern("123-test@foo_bar+baz1", "from 123-test@foo_bar+baz1");
        assertIdentifierAsIndexPattern("foo,test-*,abc", "from `foo`,`test-*`,abc");
        assertIdentifierAsIndexPattern("foo,     test-*, abc, xyz", "from `foo,     test-*, abc, xyz`");
        assertIdentifierAsIndexPattern("foo,     test-*, abc, xyz,test123", "from `foo,     test-*, abc, xyz`,     test123");
        assertIdentifierAsIndexPattern("foo,test,xyz", "from foo,   test,xyz");
        assertIdentifierAsIndexPattern(
            "<logstash-{now/M{yyyy.MM}}>,<logstash-{now/d{yyyy.MM.dd|+12:00}}>",
            "from <logstash-{now/M{yyyy.MM}}>, `<logstash-{now/d{yyyy.MM.dd|+12:00}}>`"
        );
    }
    public void testIdentifierAsFieldName() {
        String[] operators = new String[] { "==", "!=", ">", "<", ">=", "<=" };
        Class<?>[] expectedOperators = new Class<?>[] {
            Equals.class,
            Not.class,
            GreaterThan.class,
            LessThan.class,
            GreaterThanOrEqual.class,
            LessThanOrEqual.class };
        String[] identifiers = new String[] { "abc", "`abc`", "ab_c", "a.b.c", "@a", "a.@b", "`a@b.c`" };
        String[] expectedIdentifiers = new String[] { "abc", "abc", "ab_c", "a.b.c", "@a", "a.@b", "a@b.c" };
        LogicalPlan where;
        for (int i = 0; i < operators.length; i++) {
            for (int j = 0; j < identifiers.length; j++) {