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* Extend phrase by an example
@ 2018-09-08 11:56 PG Doc comments form <[email protected]>
2018-09-09 15:11 ` Re: Extend phrase by an example David G. Johnston <[email protected]>
0 siblings, 1 reply; 2+ messages in thread
From: PG Doc comments form @ 2018-09-08 11:56 UTC (permalink / raw)
To: [email protected]; +Cc: [email protected]
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/10/static/rowtypes.html
Description:
Hi.
On the page:
https://www.postgresql.org/docs/10/static/rowtypes.html
>then the same inventory_item composite type shown above would come into
being as a byproduct, and could be used just as above. Note however an
important restriction of the current implementation: since no constraints
are associated with a composite type, the constraints shown in the table
definition do not apply to values of the composite type outside the table.
(A partial workaround is to use domain types as members of composite
types.)
The part:
>(A partial workaround is to use domain types as members of composite
types.)
From here I can understand that workaround is possible.
But what is workaround? and why it is partial?
Would be great to have this description.
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Extend phrase by an example
2018-09-08 11:56 Extend phrase by an example PG Doc comments form <[email protected]>
@ 2018-09-09 15:11 ` David G. Johnston <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: David G. Johnston @ 2018-09-09 15:11 UTC (permalink / raw)
To: [email protected] <[email protected]>; [email protected] <[email protected]>
On Saturday, September 8, 2018, PG Doc comments form <[email protected]>
wrote:
> the constraints shown in the table
> definition do not apply to values of the composite type outside the table.
> (A partial workaround is to use domain types as members of composite
> types.)
>
> The part:
> >(A partial workaround is to use domain types as members of composite
> types.)
>
> From here I can understand that workaround is possible.
>
> But what is workaround? and why it is partial?
> Would be great to have this description.
>
The main thing is that some constraints are implemented via triggers and
those can only be attached to actual tables. So in the example the
REFERENCES constraint can only be used on the original table records and
can never applied to a standalone value of that type.
David J.
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