问题
I would like to create a more specific error message for Postgres CHECK IN violations. So for example a violation of the following CHECK constraint on a column:
management_zone varchar(15) NOT NULL CHECK (management_zone IN ('Marine', 'Terrestrial') ),
should return a custom error message such as ie.: "Hint: Check spelling. Only allowed inputs are: 'Marine', 'Terrestrial'.
The best solution I have seen so far solves it by using the error message as the name of the check constraint, ie
ADD CONSTRAINT c_managementzone_@Check_spelling._Only_allowed_inputs_are:_'Marine',_'Terrestrial' CHECK (management_zone IN ('Marine', 'Terrestrial') ),
and then applying a function that fixes the error message after the @ sign by replacing the underscores with space to make it more readable. The function is then called using a try and catch statement.
This code however is in t-sql which I am unfamiliar with, and I also don't know enough PL/pgSQL to be able to convert and replicate it. I therefore wonder if anyone can suggest how something similar can be done in postgres, ex. using a function and a trigger?
The t-sql code and explanation is available from here and I copy paste it below: https://social.technet.microsoft.com/wiki/contents/articles/29187.t-sql-error-handling-for-check-constraints.aspx
CREATE FUNCTION dbo.ufnGetClearErrorMessage2()
RETURNS NVARCHAR(4000)
AS
BEGIN
DECLARE @Msg NVARCHAR(4000) = ERROR_MESSAGE() ;
DECLARE @ErrNum INT = ERROR_NUMBER() ;
DECLARE @ClearMessage NVARCHAR(4000) ;
IF @ErrNum = 547
BEGIN
/*--how to find @ClearMessage:
SELECT @msg ,
CHARINDEX('@', @msg) ,
RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg)) ,
CHARINDEX('"', RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg))) ,
LEFT(RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg)), CHARINDEX('"', RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg))) - 1 ) ,
REPLACE(LEFT(RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg)), CHARINDEX('"', RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg))) - 1 ), '_', SPACE(1)) + '.'
*/
SELECT @ClearMessage = @Msg + CHAR(13) +
REPLACE(LEFT(RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg)), CHARINDEX('"', RIGHT(@msg, LEN(@msg) - CHARINDEX('@', @msg))) - 1 ), '_', SPACE(1)) + '.'
END
ELSE
SET @ClearMessage = @Msg ;
RETURN @ClearMessage ;
END
Try and catch:
BEGIN TRY
INSERT dbo.Book
( BookId, WritingDate, publishDate )
VALUES ( 1, GETDATE(), GETDATE() + 1 )
END TRY
BEGIN CATCH
DECLARE @Msg NVARCHAR(4000) = dbo.ufnGetClearErrorMessage2();
THROW 60001, @Msg, 1;
END CATCH
Any advice much apreciated.
回答1:
If you can live with a slightly different check constraint, you can do the following:
Create a function that checks the values:
create function check_zone(p_input text)
returns boolean
as
$$
declare
l_allowed text[] := array['Marine', 'Terrestrial'];
begin
if p_input = any(l_allowed) then
return true;
end if;
raise 'The only allowed values are: %', array_to_string(l_allowed, ', ');
end;
$$
language plpgsql
immutable;
And then use that function instead of an IN condition:
create table data
(
management_zone text not null,
CONSTRAINT check_zone CHECK (check_zone(management_zone))
);
The following INSERT
insert into data values ('foo');
will result in:
ERROR: The only allowed values are: Marine, Terrestrial
来源:https://stackoverflow.com/questions/53448473/custom-error-message-for-postgresql-check-in-list-constraint