Re: function to_char(unknown) is not unique at character 8

[gzh <gzhcoder@xxxxxxx>]

Thank you for the solution you provided to identify these useless usage of this function，I learned a lot from it.

At 2023-07-06 22:42:38, "Pavel Stehule" <pavel.stehule@xxxxxxxxx> wrote:

čt 6. 7. 2023 v 16:28 odesílatel gzh <gzhcoder@xxxxxxx> napsal:

Thank you for the solution, it works fine.

> I have a question. Why do you use the to_char(string) function? Instead to_char('text') you can write only 'text'.

I'm guessing it's probably a bug made by the original developer,

but I'm not sure how many bugs there are, because it works fine in older version(orafce 3.13).

you can use another version

CREATE OR REPLACE FUNCTION oracle.to_char(text)

RETURNS text AS $$

BEGIN

  RAISE WARNING 'using useless to_char function';

  RETURN $1;

END;

$$ LANGUAGE plpgsql IMMUTABLE;

This can help to identify these useless usage of this function

Unfortunately, the Oracle type system is very different, so it is hard to emulate in Postgres. And Oracle PL/SQL design allows people to write terribly ugly code. These bad things are hard to repeat in Pg.

 

At 2023-07-06 19:54:19, "Pavel Stehule" <pavel.stehule@xxxxxxxxx> wrote:

čt 6. 7. 2023 v 13:38 odesílatel gzh <gzhcoder@xxxxxxx> napsal:

Thank you very much for taking the time to reply to my question. 

There are a lot of TO_CHAR in my application, and there is a high cost of modifying the code, 

is there another solution to solve the problem without modifying the code?

There is one dirty workaround, and because it is dirty, I don't want to push it to orafce.

You can create own function to_char

CREATE OR REPLACE FUNCTION oracle.to_char(text)

RETURNS text AS $$

SELECT $1

$$ LANGUAGE sql IMMUTABLE STRICT;

This version will be preferred and fix this issue. On second thought, the behavior can be a little bit different than before.

I have a question. Why do you use the to_char(string) function? Instead to_char('text') you can write only 'text'.

 

At 2023-07-06 19:21:24, "Pavel Stehule" <pavel.stehule@xxxxxxxxx> wrote:

Hi

čt 6. 7. 2023 v 11:19 odesílatel gzh <gzhcoder@xxxxxxx> napsal:

Hi, 

I upgraded the version of PostgreSQL from 12.6 to 12.13, 

when I execute the sql below , the to_char function caused the following error.

---------------SQL------------------

select TO_CHAR('1000000');

ERROR:  function to_char(unknown) is not unique at character 8

HINT:  Could not choose a best candidate function. You might need to add explicit type casts.

There is no problem before the upgrade and to_char function comes from the Orafce extension.

The configuration of the old and new databases is as follows.

Database server (old): PostgreSQL 12.6（orafce3.13）

Database server (new): PostgreSQL 12.13（orafce3.24）

The new database has successfully installed the orafce 3.24 extension.

It does not occur in "PostgreSQL 12.6 and orafce 3.13", 

but occurs in "PostgreSQL 12.13 and orafce 3.24", 

so either the difference between 12.6 and 12.13 or the difference between orafce 3.13 and 3.24 is suspicious.

What is the reason for the problem and how to fix the error?

The new orafce contains to_char for numeric types and to_char for timestamp. Old orafce had to_char function (with one argument) only for numeric types.

This is the reason why the system doesn't know if a string of unknown type (postgresql string literal) should be processed as numeric or as a timestamp.

The best fix is specify used type like

(2023-07-06 13:19:33) postgres=# select oracle.TO_CHAR('1000000'::int);
┌─────────┐
│ to_char │
╞═════════╡
│ 1000000 │
└─────────┘
(1 row)

Regards

Pavel

Regards