Scan on hash key attribute does not return result with some comparison operators

[Andrii Ostapenko]

When we perform scan operation using hash key attribute in scan filter with comparison operators other than "EQ", we do not always get proper result.
Example:
Table with 2 key attributes:
{
"table_name": "test_table",
"attribute_definitions": [
        {
        "attribute_name": "hash_attr",
        "attribute_type": "S"
        },
        {
        "attribute_name": "range_attr",
        "attribute_type": "S"
        }
],
"key_schema": [
        {
        "attribute_name": "hash_attr",
        "key_type": "HASH"
        },
        {
        "attribute_name": "range_attr",
        "key_type": "RANGE"
        }
]
}

Puting item:
{
        "item": {
                "hash_attr": {"S": "Hello"},
                "range_attr": {"S": "World"}
        }
}

Scanning:
{
"scan_filter": {
        "hash_attr": {
                "attribute_value_list": [{"S": "Hel"}] ,
                "comparison_operator": "BEGINS_WITH"
        }
}
}

Result:
{"count": 0, "items": [], "scanned_count": 0}