| From: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
|---|---|
| To: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Arthur Zakirov <a(dot)zakirov(at)postgrespro(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Another oddity in handling of WCO constraints in postgres_fdw |
| Date: | 2018-03-09 11:55:46 |
| Message-ID: | 5AA27642.4040905@lab.ntt.co.jp |
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| Lists: | pgsql-hackers |
Hi Ashutosh,
(2018/03/08 14:24), Ashutosh Bapat wrote:
> Etsuro said [2] that WCO constraints can not be implemented on foreign
> server and normal check constraints can be, and for that he provides
> an example in [3]. But I think that example is going the wrong
> direction.
More precisely, what I'm saying there is: for WCO constraints created by
an auto-updatable view over a foreign table, we cannot always implement
constraints on the remote side that match with those WCO constraints.
> For local constraints to be enforced, we use remote
> constraints. For local WCO we need to use remote WCO. That means we
> create many foreign tables pointing to same local table on the foreign
> server through many views, but it's not impossible.
Maybe I don't understand this correctly, but I guess that it would be
the user's responsibility to not create foreign tables in such a way.
Best regards,
Etsuro Fujita
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