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Date: Tue, 7 May 2024 09:43:58 -0700
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Subject: Re: PERIOD foreign key feature
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From: Paul Jungwirth <pj@illuminatedcomputing.com>
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On 5/7/24 08:23, David G. Johnston wrote:
> On Tue, May 7, 2024 at 7:54 AM Bruce Momjian <bruce@momjian.us <mailto:bruce@momjian.us>> wrote:
>     In the two marked lines, it says "if one side of the foreign key uses
>     PERIOD, the other side must too."  However, looking at the example
>     queries, it seems like if the foreign side has PERIOD, the primary side
>     must have WITHOUT OVERLAPS, not PERIOD.
> 
>     Does this doc text need correcting?
> 
> 
> The text is factually correct, though a bit hard to parse.
> 
> "the other side" refers to the part after "REFERENCES":
> 
> FOREIGN KEY ( column_name [, ... ] [, PERIOD column_name ] ) REFERENCES reftable [ ( refcolumn [, 
> ... ] [, PERIOD column_name ] ) ]
> 
> ***(shouldn't the second occurrence be [, PERIOD refcolum] ?)
> 
> The text is pointing out that since the refcolumn specification is optional you may very well not 
> see a second PERIOD keyword in the clause.  Instead it will be inferred from the PK.
> 
> Maybe:
> 
> Finally, if the foreign key has a PERIOD column_name specification the corresponding refcolumn, if 
> present, must also be marked PERIOD.  If the refcolumn clause is omitted, and thus the reftable's 
> primary key constraint chosen, the primary key must have its final column marked WITHOUT OVERLAPS.

Yes, David is correct here on all points. I like his suggestion to clarify the language here also. 
If you need a patch from me let me know, but I assume it's something a committer can just make happen?

Yours,

-- 
Paul              ~{:-)
pj@illuminatedcomputing.com