Subject: Re: Improve new hash partition bound check error messages
To: Heikki Linnakangas <hlinnaka@iki.fi>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
References: <bb9d60b4-aadb-607a-1a9d-fdc3434dddcd@enterprisedb.com>
 <9fc7eb48-0e8f-0836-8def-bc4b242e9c63@iki.fi>
From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Organization: EnterpriseDB
Message-ID: <aeb41d57-da42-b46d-bfc1-4933afbc5658@enterprisedb.com>
Date: Wed, 3 Feb 2021 15:52:51 +0100
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On 2021-02-02 13:26, Heikki Linnakangas wrote:
> How about this?
> 
> CREATE TABLE fail_part PARTITION OF hash_parted FOR VALUES WITH (MODULUS
> 25, REMAINDER 3);
> ERROR:  every hash partition modulus must be a factor of the next larger
> modulus
> DETAIL:  25 is not divisible by 10, the modulus of existing partition
> "hpart_1"

I don't know if we can easily get the name of the existing partition. 
I'll have to check that.

I'm worried that this phrasing requires the user to understand that 
"divisible by" is related to "factor of", which is of course correct but 
introduces yet more complexity into this.

I'll play around with this a bit more.