Re: [HACKERS] logical replication syntax (was DROP SUBSCRIPTION,query cancellations and slot handling) - Mailing list pgsql-hackers

From Masahiko Sawada
Subject Re: [HACKERS] logical replication syntax (was DROP SUBSCRIPTION,query cancellations and slot handling)
Date
Msg-id CAD21AoDwJHTPn9ZN34AVLZrCD4BqSfKUJnnuGMaks2O_0RZrbQ@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] logical replication syntax (was DROP SUBSCRIPTION,query cancellations and slot handling)  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
Responses Re: [HACKERS] logical replication syntax (was DROP SUBSCRIPTION,query cancellations and slot handling)  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
List pgsql-hackers
On Tue, May 9, 2017 at 2:07 PM, Peter Eisentraut
<peter.eisentraut@2ndquadrant.com> wrote:
> On 5/8/17 23:23, Peter Eisentraut wrote:
>> The way this uses RESTRICT and CASCADE appears to be backwards from its
>> usual meaning.  Normally, CASCADE when dropping an object that is still
>> used by others will cause those other objects to be dropped.  The
>> equivalent here would be DROP REPLICATION SLOT + CASCADE would drop the
>> subscription.
>>
>> What we want to simulate instead is an "auto" dependency of the slot on
>> the subscription.  So you can drop the slot separately (subject to other
>> restrictions), and it is dropped automatically when the subscription is
>> dropped.  To avoid that, you can disassociate the slot from the
>> subscription, which you have implemented.
>>
>> I think we can therefore do without RESTRICT/CASCADE here.  If a slot is
>> associated with the subscription, it should be there when we drop the
>> subscription.  Otherwise, the user has to disassociate the slot and take
>> care of it manually.  So just keep the "cascade" behavior.
>>
>> Similarly, I wouldn't check first whether the slot exists.  If the
>> subscription is associated with the slot, it should be there.
>
> Here is your patch amended for that.
>

I think we should change tab-completion support for that as well.

diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 183fc37..046fdd5 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -2684,7 +2684,7 @@ psql_completion(const char *text, int start, int end)
       /* DROP SUBSCRIPTION */       else if (Matches3("DROP", "SUBSCRIPTION", MatchAny))
-               COMPLETE_WITH_LIST2("DROP SLOT", "NODROP SLOT");
+               COMPLETE_WITH_LIST2("CASCADE", "RESTRICT");
/* EXECUTE */       else if (Matches1("EXECUTE"))

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center



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