functions do not handle missing value well

[galkk]

Functions do not handle missing value from an document well.

Test data

Based on https://partiql.org/tutorial.html#tuples-with-missing-attributes.

PUT /employess_with_missing/_doc/3?pretty
{
  "name": "Bob Smith"
}

PUT /employess_with_missing/_doc/4?pretty
{
  "name": "Susan Smith", "title": "Dev Mgr", "age": 33
}


PUT /employess_with_missing/_doc/6?pretty
{
  "name": "Jane Smith", "title": "Software Eng 2", "age": 25
}

String funtion trim: error

GET /_opendistro/_sql/_explain
{
  "query": "SELECT e.name, TRIM(e.title) as outputTitle from employess_with_missing"
}

Returns

        "type": "script_exception",
        "reason": "runtime error",
        "script_stack": [
          "org.elasticsearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:94)",
          "org.elasticsearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:41)",
          "trim_1018882869 = doc['e.title'].value.trim();",
          "                      ^---- HERE"
        ],
        "script": "def trim_1018882869 = doc['e.title'].value.trim();return trim_1018882869;",
        "lang": "painless"
      }

Expected result:

  {
    'id': 3,
    'employeeName': 'Bob Smith'
  },
  {
    'id': 4,
    'employeeName': 'Susan Smith',
    'outputTitle': 'Dev Mgr'
  },
  {
    'id': 6,
    'employeeName': 'Jane Smith',
    'outputTitle': 'Software Eng 2'
  }

Numerical function error

GET /_opendistro/_sql
{
  "query": "SELECT e.name from employess_with_missing e WHERE sqrt(age) > 27"
}

Has the same error about missing field, while it should return all names from table