show how logical decoding is controlled over the
    streaming replication protocol, using the
    program <xref linkend="app-pgrecvlogical"/> included in the PostgreSQL
    distribution.  This requires that client authentication is set up to allow
    replication connections
    (see <xref linkend="streaming-replication-authentication"/>) and
    that <varname>max_wal_senders</varname> is set sufficiently high to allow
    an additional connection.  The second example shows how to stream two-phase
    transactions.  Before you use two-phase commands, you must set
    <xref linkend="guc-max-prepared-transactions"/> to at least 1.
   </para>
<programlisting>
Example 1:
$ pg_recvlogical -d postgres --slot=test --create-slot
$ pg_recvlogical -d postgres --slot=test --start -f -
<keycombo action="simul"><keycap>Control</keycap><keycap>Z</keycap></keycombo>
$ psql -d postgres -c "INSERT INTO data(data) VALUES('4');"
$ fg
BEGIN 693
table public.data: INSERT: id[integer]:4 data[text]:'4'
COMMIT 693
<keycombo action="simul"><keycap>Control</keycap><keycap>C</keycap></keycombo>
$ pg_recvlogical -d postgres --slot=test --drop-slot

Example 2:
$ pg_recvlogical -d postgres --slot=test --create-slot --two-phase
$ pg_recvlogical -d postgres --slot=test --start -f -
<keycombo action="simul"><keycap>Control</keycap><keycap>Z</keycap></keycombo>
$ psql -d postgres -c "BEGIN;INSERT INTO data(data) VALUES('5');PREPARE TRANSACTION 'test';"
$ fg
BEGIN 694
table public.data: INSERT: id[integer]:5 data[text]:'5'
PREPARE TRANSACTION 'test', txid 694
<keycombo action="simul"><keycap>Control</keycap><keycap>Z</keycap></keycombo>
$ psql -d postgres -c "COMMIT PREPARED 'test';"
$ fg
COMMIT PREPARED 'test', txid 694
<keycombo action="simul"><keycap>Control</keycap><keycap>C</keycap></keycombo>
$ pg_recvlogical -d postgres --slot=test --drop-slot
</programlisting>

  <para>
  The following example shows SQL interface that can be used to decode prepared
  transactions. Before you use two-phase commit commands, you must set
  <varname>max_prepared_transactions</varname> to at least 1. You must also have
  set the two-phase parameter as 'true' while creating the slot using
  <function>pg_create_logical_replication_slot</function>
  Note that we will stream the entire transaction after the commit if it
  is not already decoded.
  </para>
<programlisting>
postgres=# BEGIN;
postgres=*# INSERT INTO data(data) VALUES('5');
postgres=*# PREPARE TRANSACTION 'test_prepared1';

postgres=# SELECT * FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL);
    lsn    | xid |                          data
-----------+-----+---------------------------------------------------------
 0/1689DC0 | 529 | BEGIN 529
 0/1689DC0 | 529 | table public.data: INSERT: id[integer]:3 data[text]:'5'
 0/1689FC0 | 529 | PREPARE TRANSACTION 'test_prepared1', txid 529
(3 rows)

postgres=# COMMIT PREPARED 'test_prepared1';
postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
    lsn    | xid |                    data
-----------+-----+--------------------------------------------
 0/168A060 | 529 | COMMIT PREPARED 'test_prepared1', txid 529
(4 row)

postgres=#-- you can also rollback a prepared transaction
postgres=# BEGIN;
postgres=*# INSERT INTO data(data) VALUES('6');
postgres=*# PREPARE TRANSACTION 'test_prepared2';
postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
    lsn    | xid |                          data
-----------+-----+---------------------------------------------------------
 0/168A180 | 530 | BEGIN 530
 0/168A1E8 | 530 | table public.data: INSERT: id[integer]:4 data[text]:'6'
 0/168A430 | 530 | PREPARE TRANSACTION 'test_prepared2', txid 530
(3 rows)

postgres=# ROLLBACK PREPARED 'test_prepared2';
postgres=# select * from pg_logical_slot_get_changes('regression_slot', NULL, NULL);
    lsn    | xid |                     data
-----------+-----+----------------------------------------------
 0/168A4B8 | 530 |