Date: Thu, 17 Oct 2024 09:08:26 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Koen De Groote <kdg.dev@gmail.com>
Cc: pgsql-docs@lists.postgresql.org
Subject: Re: Logical replication - initial data synchronization
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On Thu, Oct 17, 2024 at 10:59:51AM +0200, Koen De Groote wrote:
> Hello Bruce, thanks for picking this up.
> 
> Personally, I would make explicit mention of the fact that creating the
> snapshot and copying the data is taken care of by Postgres itself. Those are
> the points that had me confused early on, wondering if I had to perform the
> copy once the snapshot was ready.

Updated patch attached.  I tried to tighten up the wording and add more
detail.  I didn't see the point in repeating the same paragraph later on
so I removed it.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  When a patient asks the doctor, "Am I going to die?", he means 
  "Am I going to die soon?"

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diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
new file mode 100644
index 98a7ad0..f104125
*** a/doc/src/sgml/logical-replication.sgml
--- b/doc/src/sgml/logical-replication.sgml
***************
*** 24,33 ****
   </para>
  
   <para>
!   Logical replication of a table typically starts with taking a snapshot
!   of the data on the publisher database and copying that to the subscriber.
!   Once that is done, the changes on the publisher are sent to the subscriber
!   as they occur in real-time.  The subscriber applies the data in the same
    order as the publisher so that transactional consistency is guaranteed for
    publications within a single subscription.  This method of data replication
    is sometimes referred to as transactional replication.
--- 24,34 ----
   </para>
  
   <para>
!   When logical replication of a table typically starts, a snapshot is
!   taken of the table's data on the publisher database and copied to the
!   subscriber.  Once complete, changes on the publisher since the initial
!   copy are sent continually to the subscriber.  The subscriber applies
!   the data in the same
    order as the publisher so that transactional consistency is guaranteed for
    publications within a single subscription.  This method of data replication
    is sometimes referred to as transactional replication.
***************
*** 165,171 ****
     The individual tables can be added and removed dynamically using
     <link linkend="sql-alterpublication"><command>ALTER PUBLICATION</command></link>.  Both the <literal>ADD
     TABLE</literal> and <literal>DROP TABLE</literal> operations are
!    transactional; so the table will start or stop replicating at the correct
     snapshot once the transaction has committed.
    </para>
   </sect1>
--- 166,172 ----
     The individual tables can be added and removed dynamically using
     <link linkend="sql-alterpublication"><command>ALTER PUBLICATION</command></link>.  Both the <literal>ADD
     TABLE</literal> and <literal>DROP TABLE</literal> operations are
!    transactional, so the table will start or stop replicating at the correct
     snapshot once the transaction has committed.
    </para>
   </sect1>
*************** CONTEXT:  processing remote data for rep
*** 1953,1967 ****
    <title>Architecture</title>
  
    <para>
-    Logical replication starts by copying a snapshot of the data on the
-    publisher database.  Once that is done, changes on the publisher are sent
-    to the subscriber as they occur in real time.  The subscriber applies data
-    in the order in which commits were made on the publisher so that
-    transactional consistency is guaranteed for the publications within any
-    single subscription.
-   </para>
- 
-   <para>
     Logical replication is built with an architecture similar to physical
     streaming replication (see <xref linkend="streaming-replication"/>).  It is
     implemented by <literal>walsender</literal> and <literal>apply</literal>
--- 1954,1959 ----

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