bug : SELECT TIMESTAMP 'now'; not working

[abhyuday26]

Describe the bug

As per #7686 we should get same result for these three queries

SELECT CURRENT_TIMESTAMP;
SELECT now();
SELECT TIMESTAMP 'now';

But we encounter below error

ERROR: QueryError: Expr error: Parse error: Can't cast string to timestamp (expected format is YYYY-MM-DD HH:MM:SS[.D+{up to 6 digits}] or YYYY-MM-DD HH:MM or YYYY-MM-DD or ISO 8601 format)

Support for above two queries was given in #7695

To Reproduce

It can be simply reproduced by running this query.
SELECT TIMESTAMP 'now';

Expected behavior

It should return the current timestamp.

         timestamp
----------------------------
 2023-02-21 19:26:33.361002
(1 row)

Additional context

No response

[xiangjinwu]

Yes, TIMESTAMP 'now' is not implemented right now.

However, even though SELECT TIMESTAMP 'now';, SELECT now(); and SELECT CURRENT_TIMESTAMP; are expected to return the same result as a batch query, they have different meaning in (materialized) views. The TIMESTAMP 'now' form would be a constant equal to the time of view creation.

Let's treat this as a missing feature and decide whether we want to support it (and warn user) rather than a bug.
cc @neverchanje

[xiangjinwu]

until a valid use case raised