Re: Need help requiring uniqueness in text columns - Mailing list pgsql-general

On Wed 02 Jan 2008 04:23:46 AM EST, Pavel Stehule wrote:
> Hello
>
> IDEA 3:
>
> Use two hash functions:
>
> CREATE UNIQUE INDEX uidx ON TEST((decode(md5(a),'hex')),(hashtext(a)));
>
> removing spaces helps
> CREATE UNIQUE INDEX uidx ON test((decode(md5(lower(replace(a,' ',''))),'hex')));
>
> Regards
> Pavel Stehule
>
> CREATE UNIQUE INDEX nodups on MESSAGE (my_timestamp_col, md5(my_text_col));

What is the advantage of this method?

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