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Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.
Improve the descriptions of some options. Fix sloppy grammar and markup. Peter Smith and Tom Lane Discussion: https://postgr.es/m/CAHut+PtPJDSOxtuMGpO2yDrRPKxcYGL4n7HqJP9HernZE=Cj+g@mail.gmail.com
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‎doc/src/sgml/ref/alter_subscription.sgml‎

Lines changed: 19 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -50,14 +50,14 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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(Currently, all subscription owners must be superusers, so the owner checks
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will be bypassed in practice. But this might change in the future.)
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</para>
53-
53+
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<para>
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When refreshing a publication we remove the relations that are no longer
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part of the publication and we also remove the table synchronization slots
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if there are any. It is necessary to remove these slots so that the resources
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allocated for the subscription on the remote host are released. If due to
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network breakdown or some other error, <productname>PostgreSQL</productname>
60-
is unable to remove the slots, an ERROR will be reported. To proceed in this
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is unable to remove the slots, an error will be reported. To proceed in this
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situation, the user either needs to retry the operation or disassociate the
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slot from the subscription and drop the subscription as explained in
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<xref linkend="sql-dropsubscription"/>.
@@ -69,9 +69,11 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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option as true cannot be executed inside a transaction block.
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These commands also cannot be executed when the subscription has
72-
<literal>two_phase</literal> commit enabled, unless <literal>copy_data = false</literal>.
73-
See column <literal>subtwophasestate</literal> of
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<xref linkend="catalog-pg-subscription"/> to know the actual two-phase state.
72+
<literal>two_phase</literal> commit enabled,
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unless <literal>copy_data</literal> is <literal>false</literal>.
74+
See column <structfield>subtwophasestate</structfield> of
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<link linkend="catalog-pg-subscription"><structname>pg_subscription</structname></link>
76+
to know the actual two-phase state.
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</para>
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</refsect1>
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@@ -92,7 +94,7 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<term><literal>CONNECTION '<replaceable class="parameter">conninfo</replaceable>'</literal></term>
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<listitem>
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<para>
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This clause alters the connection property originally set by
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This clause replaces the connection string originally set by
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<xref linkend="sql-createsubscription"/>. See there for more
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information.
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</para>
@@ -105,7 +107,8 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<term><literal>DROP PUBLICATION <replaceable class="parameter">publication_name</replaceable></literal></term>
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<listitem>
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<para>
108-
Changes the list of subscribed publications. <literal>SET</literal>
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These forms change the list of subscribed publications.
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<literal>SET</literal>
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replaces the entire list of publications with a new list,
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<literal>ADD</literal> adds additional publications to the list of
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publications, and <literal>DROP</literal> removes the publications from
@@ -143,8 +146,8 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<para>
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Fetch missing table information from publisher. This will start
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replication of tables that were added to the subscribed-to publications
146-
since the last invocation of <command>REFRESH PUBLICATION</command> or
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since <command>CREATE SUBSCRIPTION</command>.
149+
since <command>CREATE SUBSCRIPTION</command> or
150+
the last invocation of <command>REFRESH PUBLICATION</command>.
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</para>
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<para>
@@ -156,9 +159,9 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<term><literal>copy_data</literal> (<type>boolean</type>)</term>
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<listitem>
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<para>
159-
Specifies whether the existing data in the publications that are
160-
being subscribed to should be copied once the replication starts.
161-
The default is <literal>true</literal>. (Previously subscribed
162+
Specifies whether to copy pre-existing data in the publications
163+
that are being subscribed to when the replication starts.
164+
The default is <literal>true</literal>. (Previously-subscribed
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tables are not copied.)
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</para>
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</listitem>
@@ -171,8 +174,8 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<term><literal>ENABLE</literal></term>
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<listitem>
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<para>
174-
Enables the previously disabled subscription, starting the logical
175-
replication worker at the end of transaction.
177+
Enables a previously disabled subscription, starting the logical
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replication worker at the end of the transaction.
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</para>
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</listitem>
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</varlistentry>
@@ -181,8 +184,8 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
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<term><literal>DISABLE</literal></term>
182185
<listitem>
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<para>
184-
Disables the running subscription, stopping the logical replication
185-
worker at the end of transaction.
187+
Disables a running subscription, stopping the logical replication
188+
worker at the end of the transaction.
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</para>
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</listitem>
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</varlistentry>

‎doc/src/sgml/ref/create_subscription.sgml‎

Lines changed: 57 additions & 50 deletions
Original file line numberDiff line numberDiff line change
@@ -32,20 +32,21 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
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<title>Description</title>
3333

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<para>
35-
<command>CREATE SUBSCRIPTION</command> adds a new subscription for the
36-
current database. The subscription name must be distinct from the name of
37-
any existing subscription in the database.
35+
<command>CREATE SUBSCRIPTION</command> adds a new logical-replication
36+
subscription. The subscription name must be distinct from the name of
37+
any existing subscription in the current database.
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</para>
3939

4040
<para>
41-
The subscription represents a replication connection to the publisher. As
42-
such this command does not only add definitions in the local catalogs but
43-
also creates a replication slot on the publisher.
41+
A subscription represents a replication connection to the publisher.
42+
Hence, in addition to adding definitions in the local catalogs, this
43+
command normally creates a replication slot on the publisher.
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</para>
4545

4646
<para>
4747
A logical replication worker will be started to replicate data for the new
48-
subscription at the commit of the transaction where this command is run.
48+
subscription at the commit of the transaction where this command is run,
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unless the subscription is initially disabled.
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</para>
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<para>
@@ -73,14 +74,15 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
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<term><literal>CONNECTION '<replaceable class="parameter">conninfo</replaceable>'</literal></term>
7475
<listitem>
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<para>
76-
The connection string to the publisher. For details
77-
see <xref linkend="libpq-connstring"/>.
77+
The <application>libpq</application> connection string defining how
78+
to connect to the publisher database. For details see
79+
<xref linkend="libpq-connstring"/>.
7880
</para>
7981
</listitem>
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</varlistentry>
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8284
<varlistentry>
83-
<term><literal>PUBLICATION <replaceable class="parameter">publication_name</replaceable></literal></term>
85+
<term><literal>PUBLICATION <replaceable class="parameter">publication_name</replaceable> [, ...]</literal></term>
8486
<listitem>
8587
<para>
8688
Names of the publications on the publisher to subscribe to.
@@ -105,25 +107,23 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
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<listitem>
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<para>
107109
Specifies whether the <command>CREATE SUBSCRIPTION</command>
108-
should connect to the publisher at all. Setting this to
109-
<literal>false</literal> will change default values of
110-
<literal>enabled</literal>, <literal>create_slot</literal> and
110+
command should connect to the publisher at all. The default
111+
is <literal>true</literal>. Setting this to
112+
<literal>false</literal> will force the values of
113+
<literal>create_slot</literal>, <literal>enabled</literal> and
111114
<literal>copy_data</literal> to <literal>false</literal>.
115+
(You cannot combine setting <literal>connect</literal>
116+
to <literal>false</literal> with
117+
setting <literal>create_slot</literal>, <literal>enabled</literal>,
118+
or <literal>copy_data</literal> to <literal>true</literal>.)
112119
</para>
113120

114121
<para>
115-
It is not allowed to combine <literal>connect</literal> set to
116-
<literal>false</literal> and <literal>enabled</literal>,
117-
<literal>create_slot</literal>, or <literal>copy_data</literal>
118-
set to <literal>true</literal>.
119-
</para>
120-
121-
<para>
122-
Since no connection is made when this option is set
123-
to <literal>false</literal>, the tables are not subscribed, and so
122+
Since no connection is made when this option is
123+
<literal>false</literal>, no tables are subscribed, and so
124124
after you enable the subscription nothing will be replicated.
125-
It is required to run
126-
<literal>ALTER SUBSCRIPTION ... REFRESH PUBLICATION</literal> in order
125+
You will need to then run
126+
<literal>ALTER SUBSCRIPTION ... REFRESH PUBLICATION</literal>
127127
for tables to be subscribed.
128128
</para>
129129
</listitem>
@@ -135,6 +135,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
135135
<para>
136136
Specifies whether the command should create the replication slot on
137137
the publisher. The default is <literal>true</literal>.
138+
If set to <literal>false</literal>, you are responsible for
139+
creating the publisher's slot in some other way.
138140
</para>
139141
</listitem>
140142
</varlistentry>
@@ -143,8 +145,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
143145
<term><literal>enabled</literal> (<type>boolean</type>)</term>
144146
<listitem>
145147
<para>
146-
Specifies whether the subscription should be actively replicating,
147-
or whether it should be just setup but not started yet. The default
148+
Specifies whether the subscription should be actively replicating
149+
or whether it should just be set up but not started yet. The default
148150
is <literal>true</literal>.
149151
</para>
150152
</listitem>
@@ -154,15 +156,15 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
154156
<term><literal>slot_name</literal> (<type>string</type>)</term>
155157
<listitem>
156158
<para>
157-
Name of the replication slot to use. The default behavior is to
158-
use the name of the subscription for the slot name.
159+
Name of the publisher's replication slot to use. The default is
160+
to use the name of the subscription for the slot name.
159161
</para>
160162

161163
<para>
162-
When <literal>slot_name</literal> is set to
163-
<literal>NONE</literal>, there will be no replication slot
164-
associated with the subscription. This can be used if the
165-
replication slot will be created later manually. Such
164+
Setting <literal>slot_name</literal> to <literal>NONE</literal>
165+
means there will be no replication slot
166+
associated with the subscription. Use this when you will be
167+
creating the replication slot later manually. Such
166168
subscriptions must also have both <literal>enabled</literal> and
167169
<literal>create_slot</literal> set to <literal>false</literal>.
168170
</para>
@@ -172,7 +174,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
172174
</para>
173175

174176
<para>
175-
The following parameters control the replication behavior:
177+
The following parameters control the subscription's replication
178+
behavior after it has been created:
176179

177180
<variablelist>
178181

@@ -183,14 +186,14 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
183186
Specifies whether the subscription will request the publisher to
184187
send the data in binary format (as opposed to text).
185188
The default is <literal>false</literal>.
186-
Even when this option is enabled, only data types that have
189+
Even when this option is enabled, only data types having
187190
binary send and receive functions will be transferred in binary.
188191
</para>
189192

190193
<para>
191-
When doing cross-version replication, it could happen that the
194+
When doing cross-version replication, it could be that the
192195
publisher has a binary send function for some data type, but the
193-
subscriber lacks a binary receive function for the type. In
196+
subscriber lacks a binary receive function for that type. In
194197
such a case, data transfer will fail, and
195198
the <literal>binary</literal> option cannot be used.
196199
</para>
@@ -201,8 +204,8 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
201204
<term><literal>copy_data</literal> (<type>boolean</type>)</term>
202205
<listitem>
203206
<para>
204-
Specifies whether the existing data in the publications that are
205-
being subscribed to should be copied once the replication starts.
207+
Specifies whether to copy pre-existing data in the publications
208+
that are being subscribed to when the replication starts.
206209
The default is <literal>true</literal>.
207210
</para>
208211
</listitem>
@@ -212,9 +215,9 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
212215
<term><literal>streaming</literal> (<type>boolean</type>)</term>
213216
<listitem>
214217
<para>
215-
Specifies whether streaming of in-progress transactions should
216-
be enabled for this subscription. By default, all transactions
217-
are fully decoded on the publisher, and only then sent to the
218+
Specifies whether to enable streaming of in-progress transactions
219+
for this subscription. By default, all transactions
220+
are fully decoded on the publisher and only then sent to the
218221
subscriber as a whole.
219222
</para>
220223
</listitem>
@@ -261,18 +264,22 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
261264
</para>
262265

263266
<para>
264-
When two-phase commit is enabled then the decoded transactions are sent
265-
to the subscriber on the PREPARE TRANSACTION. By default, the transaction
266-
prepared on the publisher is decoded as a normal transaction at commit.
267+
When two-phase commit is enabled, prepared transactions are sent
268+
to the subscriber at the time of <command>PREPARE
269+
TRANSACTION</command>, and are processed as two-phase
270+
transactions on the subscriber too. Otherwise, prepared
271+
transactions are sent to the subscriber only when committed, and
272+
are then processed immediately by the subscriber.
267273
</para>
268274

269275
<para>
270-
The two-phase commit implementation requires that the replication has
271-
successfully passed the initial table synchronization phase. This means
272-
even when two_phase is enabled for the subscription, the internal
273-
two-phase state remains temporarily "pending" until the initialization
274-
phase is completed. See column
275-
<literal>subtwophasestate</literal> of <xref linkend="catalog-pg-subscription"/>
276+
The implementation of two-phase commit requires that replication
277+
has successfully finished the initial table synchronization
278+
phase. So even when <literal>two_phase</literal> is enabled for a
279+
subscription, the internal two-phase state remains
280+
temporarily <quote>pending</quote> until the initialization phase
281+
completes. See column <structfield>subtwophasestate</structfield>
282+
of <link linkend="catalog-pg-subscription"><structname>pg_subscription</structname></link>
276283
to know the actual two-phase state.
277284
</para>
278285

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