Postgres Pro
Downloads
Home   >   mailing lists

Re: [HACKERS] Create subscription with `create_slot=false` andincorrect slot name - Mailing list pgsql-hackers

From Euler Taveira
Subject Re: [HACKERS] Create subscription with `create_slot=false` andincorrect slot name
Date
Msg-id CAHE3wghW1pgkGPmj6-Pi60Q2PjsTfrCKUNu5o5G4uKm2y5iqAA@mail.gmail.com
Whole thread Raw
In response to [HACKERS] Create subscription with `create_slot=false` and incorrect slot name  (Dmitry Dolgov <9erthalion6@gmail.com>)
Responses Re: [HACKERS] Create subscription with `create_slot=false` andincorrect slot name
List pgsql-hackers
Tree view
2017-05-22 17:52 GMT-03:00 Dmitry Dolgov <9erthalion6@gmail.com>:
Maybe this question was already raised before, but I couldn't find a
discussion. When I'm creating a subscription with `create_slot=false` looks
like it's possible to pass a slot name with invalid characters. In this
particular case both publisher and subscriber were on the same machine:

    =# CREATE SUBSCRIPTION test_sub CONNECTION 'dbname=db host=host port=port user=user' PUBLICATION test_pub WITH (create_slot=false, slot_name='test slot');
    NOTICE:  00000: synchronized table states
    LOCATION:  CreateSubscription, subscriptioncmds.c:443
    CREATE SUBSCRIPTION
    Time: 5.887 ms

The command succeed even if slot_name is invalid. That's because slot_name isn't validated. ReplicationSlotValidateName() should be called in parse_subscription_options() to avoid a pilot error. IMHO we should prevent a future error (use of invalid slot name).
 
Of course `test slot` doesn't exist, because I can't create a slot with
incorrect name. And consequently I can't drop this subscription:

    =# DROP SUBSCRIPTION test_sub;
    ERROR:  XX000: could not drop the replication slot "test slot" on publisher
    DETAIL:  The error was: ERROR:  replication slot name "test slot" contains invalid character
    HINT:  Replication slot names may only contain lower case letters, numbers, and the underscore character.
    LOCATION:  DropSubscription, subscriptioncmds.c:947
    Time: 2.615 ms

Indeed you can drop the subscription. There are two details: (i) subscription should be disabled and (ii) slot name can't be set.

bar=# drop subscription sub1;
ERROR:  could not drop the replication slot "does_not_exist" on publisher
DETAIL:  The error was: ERROR:  replication slot "does_not_exist" does not exist
bar=# alter subscription sub1 set (slot_name = NONE);
ERROR:  cannot set slot_name = NONE for enabled subscription
bar=# alter subscription sub1 disable;
ALTER SUBSCRIPTION
bar=# drop subscription sub1;
ERROR:  could not drop the replication slot "does_not_exist" on publisher
DETAIL:  The error was: ERROR:  replication slot "does_not_exist" does not exist
bar=# alter subscription sub1 set (slot_name = NONE);
ALTER SUBSCRIPTION
bar=# drop subscription sub1;
DROP SUBSCRIPTION

Should we add a hint for 'could not drop the replication slot' message?


--
   Euler Taveira                                   Timbira - http://www.timbira.com.br/
   PostgreSQL: Consultoria, Desenvolvimento, Suporte 24x7 e Treinamento

pgsql-hackers by date:

Previous
From: Fabien COELHO
Date:
Subject: Re: [HACKERS] psql - add special variable to reflect the last querystatus
Next
From: tushar
Date:
Subject: Re: [HACKERS] Getting server crash after running sqlsmith