PostgreSQL SQL compatibility: VARCHAR(N)

[emarsden]

Describe the bug

SELECT 'foo'::varchar(20) triggers a parse error.

Error message/log

ERROR:  Failed to run the query

Caused by:
  sql parser error: expected end of statement, found: (
LINE 1: SELECT 'foo'::varchar(20);
                              ^

To Reproduce

SELECT 'foo'::varchar(20);

Expected behavior

No response

How did you deploy RisingWave?

Via the dockerhub image.

The version of RisingWave

PostgreSQL 13.14.0-RisingWave-2.1.0 (d6e98ac)

Additional context

No response

[lmatz]

Thanks @emarsden,

in RW, the underlying implementation does not differentiate varchar(x), varchar(y), and varchar types.

So we chose to ban the varchar() ones to avoid users' confusion.

[emarsden]

OK, thanks. I see that this is documented at https://docs.risingwave.com/sql/data-types/overview. It would be useful for users to document the limitations in PostgreSQL compatibility more explicitly (I see for example that the obj_description() function from PostgreSQL does not return correct results for a "COMMENT ON TABLE ...").