[BUG] Existing field cannot be overriden with parse command

[kt-eliatra]

What is the bug? According to https://github.com/opensearch-project/sql/blob/main/docs/user/ppl/cmd/parse.rst#example-2-override-an-existing-field, the parse command can be used to override an existing field. It doesn't work in spark ppl.

How can one reproduce the bug? Steps to reproduce the behavior:

1. Create table and add data

   
   CREATE TABLE test (
   name STRING, age INT, email STRING, street_address STRING
   );

INSERT INTO test VALUES ("Alice", 30, "alice@example.com", "123 Main St, Seattle"), ("Bob", 55, "bob@test.org", "456 Elm St, Portland"), ("Charlie", 65, "charlie@domain.net", "789 Pine St, San Francisco"), ("David", 19, "david@anotherdomain.com", "101 Maple St, New York");

2. Run command like

source=test | parse email '.+@(?.+)' | fields email;

3. It returns

[AMBIGUOUS_REFERENCE] Reference email is ambiguous, could be: [email, spark_catalog.default.test.email].

**What is the expected behavior?**
Values from the existing email column are overridden by values computed by the parse command.

**What is your host/environment?**
 - OS: Linux Mint

**Do you have any screenshots?**
If applicable, add screenshots to help explain your problem.

**Do you have any additional context?**
Add any other context about the problem.

[salyh]

Is it even possible to replace a existing column with a new computed column with same name in spark? Not sure about this.

[dblock]

[Catch All Triage - 1, 2, 3, 4]