Thread: Postgres 8 - problem: invalid input syntax for integer
Hi, In previous version di Postgres (7.2) I used this table: CREATE TABLE tablename (id serial, field int1, field2 text); Now this query work: UPDATE tablename SET field1=''; (NOTE: implicit conversion to 0) UPDATE tablename SET field2=''; (this cause of simple code-generation query - I don't know what's field type) Now in postgres 8 this don't work. Why ?(ok, it's the ufficial documentation but I don't understand... why? it's so comfortable!) Can someone help me to create a CAST to re-use this feature? Thank you! Mauro
mauro wrote:
> Hi, In previous version di Postgres (7.2) I used this table:
> CREATE TABLE tablename (id serial, field int1, field2 text);
>
> Now this query work:
> UPDATE tablename SET field1=''; (NOTE: implicit conversion to 0)
> UPDATE tablename SET field2='';
>
> (this cause of simple code-generation query - I don't know what's
> field type)
Know your field-types. If you don't know what they are, you can't handle
errors elegantly anyway.
> Now in postgres 8 this don't work.
> Why ?(ok, it's the ufficial documentation but I don't understand...
> why? it's so comfortable!)
What number does '' represent?
Does that mean a string of '/2' should equal your number divided by two?
If not, why not?
Who is providing an empty string where you've asked for a number, and
why not trap this error (or store a NULL)?
> Can someone help me to create a CAST to re-use this feature?
Well, you could create a function:
CREATE FUNCTION empty_string_is_zero(text) RETURNS integer AS ' SELECT CASE WHEN $1='''' THEN 0 ELSE $1::integer
END;
' LANGUAGE SQL;
UPDATE my_table SET myfield=empty_string_is_zero('');
HTH
-- Richard Huxton Archonet Ltd
> What number does '' represent?
'No response' value...
> Does that mean a string of '/2' should equal your number divided by two?
right, but it is never required.
> If not, why not?
because I use it to GROUP BY values.
> Who is providing an empty string where you've asked for a number, and
> why not trap this error (or store a NULL)?
You are certainly right. My problem concerns the compatibility of code
among postgres 8 and 7.2 that I wanted to maintain. The existing code
(data analysis) exploits the particularity that the null ('') becomes
0 (ok, no comment :) ) logically wrong but practically perfect!
[...CAST CODE...]
Thank you for the explicit-cast code, but I want reproduce it in
'database level' so I don't use explicit cast but IMPLICIT; everytime
updating integer fields with '' values it cast to (0 or NULL).
Best regards, Mauro
mauro wrote:
>>What number does '' represent?
>
> 'No response' value...
Would've been better to have a genuine response_provided flag, but then
you obviously know that.
>>Who is providing an empty string where you've asked for a number, and
>>why not trap this error (or store a NULL)?
>
> You are certainly right. My problem concerns the compatibility of code
> among postgres 8 and 7.2 that I wanted to maintain. The existing code
> (data analysis) exploits the particularity that the null ('') becomes
> 0 (ok, no comment :) ) logically wrong but practically perfect!
Your best choice is probably to tweak your application and translate ''
to NULL? Then you could add a before trigger to the table to replace
NULL with 0.
> [...CAST CODE...]
>
> Thank you for the explicit-cast code, but I want reproduce it in
> 'database level' so I don't use explicit cast but IMPLICIT; everytime
> updating integer fields with '' values it cast to (0 or NULL).
If you can't do the above, you've got three options: 1. Stay with PG version 7.2 2. Write your own type, with in/out
functionsthat map '' to 0 3. Hack the code to replace the ''=>0 conversion - you could probably
identify the old code from CVS.
Obviously the null+trigger option is better than these three. Of these
three though, number 2 is probably the cleanest solution.
-- Richard Huxton Archonet Ltd