Re: "Multiple table synchronizations are processed serially" still happens - Mailing list pgsql-hackers

From Guillaume Lelarge
Subject Re: "Multiple table synchronizations are processed serially" still happens
Date
Msg-id CAECtzeVNd+o9LUnRGA_6KpugcsS_6o2241DosSdsEe4=933ABg@mail.gmail.com
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In response to Re: "Multiple table synchronizations are processed serially" still happens  (Amit Kapila <amit.kapila16@gmail.com>)
Responses Re: "Multiple table synchronizations are processed serially" still happens
List pgsql-hackers
Hi,

Le jeu. 20 mai 2021 à 12:09, Amit Kapila <amit.kapila16@gmail.com> a écrit :
On Wed, Apr 28, 2021 at 2:43 PM Guillaume Lelarge
<guillaume@lelarge.info> wrote:
>
> And it logs the "still waiting" message as long as the first table is being synchronized. Once this is done, it releases the lock, and the synchronization of the second table starts.
>
> Is there something I didn't understand on the previous thread?
>

It seems from a script that you are creating a subscription on the
same node as publication though in a different DB, right?

Yes, that's right.

If so, the
problem might be that copying the data of the first table creates a
transaction which blocks creation of the slot for second table copy.

I don't understand how a transaction could block the creation of a slot. Could you explain that to me? or do you know where this is explained in the documentation?

The commit you referred will just fix the problem while reading the
data from the publisher not while writing data in the table in the
subscriber.

> I'd like to know why serial synchronization happens, and if there's a way to avoid it.
>

I guess you need to create a subscription on a different node.


Thanks.


--
Guillaume.

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