Re: Determine length of numeric field

On 2011-02-15, Tony Capobianco <tcapobianco(at)prospectiv(dot)com> wrote:
> I'm altering datatypes in several tables from numeric to integer. In
> doing so, I get the following error:
>
> dw=# \d uniq_hits
> Table "support.uniq_hits"
> Column | Type | Modifiers
> ------------+---------+-----------
> sourceid | numeric |
> hitdate | date |
> total | numeric |
> hitdate_id | integer |
> Indexes:
> "uniq_hits_hitdateid_idx" btree (hitdate_id), tablespace
> "support_idx"
> Tablespace: "support"
>
> esave_dw=# alter table uniq_hits alter sourceid type int;
> ERROR: integer out of range
>
> Sourceid should not be more than 5 digits long. I'm able to perform
> this query on Oracle and would like something similar on postgres 8.4:
>
> delete from uniq_hits where sourceid in (select sourceid from uniq_hits
> where length(sourceid) > 5);

delete from uniq_hits where sourceid in (select sourceid from uniq_hits
where length(sourceid::text) > 5);

or even: delete from uniq_hits where length(sourceid::text) > 5;

but using length on numbers is usually the wrong way.

do this instead: delete from uniq_hits where abs(sourceid) > 2^32-1;

Which will hit all the ones that can't be converted.

You may want to do a select first to see what you're deleting.

> I haven't had much luck with the length or char_length functions on
> postgres.

The length functions only work with strings. using them on numbers is
usually the wrong thing as there is not a 1 to 1 mapping between
strings an numbers.

Strings of length only 3 can be out of range for integer (eg: '9e9'),
(but numerics never look like that, larger floats can though)

care to guess the result of this query?

select '9000000000000000'::float, length('9000000000000000'::float::text);

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