Re: Conditional INSERT

> On Mar 15, 2019, at 12:59 PM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> wrote:
>
> On 3/15/19 11:54 AM, basti wrote:
>> this is a dns database, and the client is update the _acme-challenge for
>> LE certificates. I don't want that the client can insert "any" txt record.
>> the client should only insert data if the hostname start with
>> _acme-challenge. i have no control on client.
>> i have try this rule but the server reject this with a endless loop:
>
> To borrow a quote:
>
> "I had a problem so I decided to use a rule, now I have two problems."
>
> Do not use a rule. As suggested upstream use a BEFORE INSERT trigger, you will be a lot happier.
>
>> CREATE RULE insert_acme AS ON INSERT TO t_dnsadmin_records_txt
>> WHERE NEW.hostname like '_acme-challenge%'
>> DO INSERT INTO t_dnsadmin_records_txt VALUES (
>> NEW.domainid,
>> NEW.hostname,
>> NEW.txtdata
>> );
>> On 15.03.19 19:17, Michael Lewis wrote:
>>> On Fri, Mar 15, 2019 at 10:55 AM basti <mailinglist(at)unix-solution(dot)de
>>> <mailto:mailinglist(at)unix-solution(dot)de>> wrote:
>>>
>>> Hello,
>>>
>>> I want to insert data into table only if condition is true.
>>> For example:
>>>
>>> INSERT into mytable (domainid, hostname, txtdata)
>>> VALUES (100,'_acme.challenge.example', 'somedata');
>>>
>>> Alternative to a trigger implementation, if you are generating that
>>> INSERT statement, you can change it to use a sub-select or CTE that
>>> contains no values if the domainid isn't what you like. If you want it
>>> to fail with error, you could add a check constraint. We might need more
>>> context on what you are doing and why to give good advice.
>
>

Does a check constraint not suffice in this situation?