CREATE SUBSCRIPTION — define a new subscription
CREATE SUBSCRIPTIONsubscription_nameCONNECTION 'conninfo' PUBLICATIONpublication_name[, ...] [ WITH (subscription_parameter[=value] [, ... ] ) ]
CREATE SUBSCRIPTION adds a new logical-replication
subscription. The user that creates a subscription becomes the owner
of the subscription. The subscription name must be distinct from the name of
any existing subscription in the current database.
A subscription represents a replication connection to the publisher. Hence, in addition to adding definitions in the local catalogs, this command normally creates a replication slot on the publisher.
A logical replication worker will be started to replicate data for the new subscription at the commit of the transaction where this command is run, unless the subscription is initially disabled.
To be able to create a subscription, you must have the privileges of the
the pg_create_subscription role, as well as
CREATE privileges on the current database.
Additional information about subscriptions and logical replication as a whole is available at Section 31.2 and Chapter 31.
subscription_name #The name of the new subscription.
CONNECTION 'conninfo' #The libpq connection string defining how to connect to the publisher database. For details see Section 34.1.1.
PUBLICATION publication_name [, ...] #Names of the publications on the publisher to subscribe to.
WITH ( subscription_parameter [= value] [, ... ] ) #This clause specifies optional parameters for a subscription.
The following parameters control what happens during subscription creation:
connect (boolean) #
Specifies whether the CREATE SUBSCRIPTION
command should connect to the publisher at all. The default
is true. Setting this to
false will force the values of
create_slot, enabled and
copy_data to false.
(You cannot combine setting connect
to false with
setting create_slot, enabled,
or copy_data to true.)
Since no connection is made when this option is
false, no tables are subscribed. To initiate
replication, you must manually create the replication slot, enable
the subscription, and refresh the subscription. See
Section 31.2.3
for examples.
create_slot (boolean) #
Specifies whether the command should create the replication slot on
the publisher. The default is true.
If set to false, you are responsible for
creating the publisher's slot in some other way. See
Section 31.2.3
for examples.
enabled (boolean) #
Specifies whether the subscription should be actively replicating
or whether it should just be set up but not started yet. The default
is true.
slot_name (string) #Name of the publisher's replication slot to use. The default is to use the name of the subscription for the slot name.
Setting slot_name to NONE
means there will be no replication slot associated with the
subscription. Such subscriptions must also have both
enabled and create_slot set to
false. Use this when you will be creating the
replication slot later manually. See
Section 31.2.3
for examples.
The following parameters control the subscription's replication behavior after it has been created:
binary (boolean) #
Specifies whether the subscription will request the publisher to send
the data in binary format (as opposed to text). The default is
false. Any initial table synchronization copy
(see copy_data) also uses the same format. Binary
format can be faster than the text format, but it is less portable
across machine architectures and PostgreSQL
versions. Binary format is very data type specific; for example, it
will not allow copying from a smallint column to an
integer column, even though that would work fine in text
format. Even when this option is enabled, only data types having binary
send and receive functions will be transferred in binary. Note that
the initial synchronization requires all data types to have binary
send and receive functions, otherwise the synchronization will fail
(see CREATE TYPE for more about send/receive
functions).
When doing cross-version replication, it could be that the
publisher has a binary send function for some data type, but the
subscriber lacks a binary receive function for that type. In
such a case, data transfer will fail, and
the binary option cannot be used.
If the publisher is a PostgreSQL version
before 16, then any initial table synchronization will use text format
even if binary = true.
copy_data (boolean) #
Specifies whether to copy pre-existing data in the publications
that are being subscribed to when the replication starts.
The default is true.
If the publications contain WHERE clauses, it
will affect what data is copied. Refer to the
Notes for details.
See Notes for details of how
copy_data = true can interact with the
origin parameter.
streaming (enum) #
Specifies whether to enable streaming of in-progress transactions
for this subscription. The default value is off,
meaning all transactions are fully decoded on the publisher and only
then sent to the subscriber as a whole.
If set to on, the incoming changes are written to
temporary files and then applied only after the transaction is
committed on the publisher and received by the subscriber.
If set to parallel, incoming changes are directly
applied via one of the parallel apply workers, if available. If no
parallel apply worker is free to handle streaming transactions then
the changes are written to temporary files and applied after the
transaction is committed. Note that if an error happens in a
parallel apply worker, the finish LSN of the remote transaction
might not be reported in the server log.
synchronous_commit (enum) #
The value of this parameter overrides the
synchronous_commit setting within this
subscription's apply worker processes. The default value
is off.
It is safe to use off for logical replication:
If the subscriber loses transactions because of missing
synchronization, the data will be sent again from the publisher.
A different setting might be appropriate when doing synchronous
logical replication. The logical replication workers report the
positions of writes and flushes to the publisher, and when using
synchronous replication, the publisher will wait for the actual
flush. This means that setting
synchronous_commit for the subscriber to
off when the subscription is used for
synchronous replication might increase the latency for
COMMIT on the publisher. In this scenario, it
can be advantageous to set synchronous_commit
to local or higher.
two_phase (boolean) #
Specifies whether two-phase commit is enabled for this subscription.
The default is false.
When two-phase commit is enabled, prepared transactions are sent
to the subscriber at the time of PREPARE
TRANSACTION, and are processed as two-phase
transactions on the subscriber too. Otherwise, prepared
transactions are sent to the subscriber only when committed, and
are then processed immediately by the subscriber.
The implementation of two-phase commit requires that replication
has successfully finished the initial table synchronization
phase. So even when two_phase is enabled for a
subscription, the internal two-phase state remains
temporarily “pending” until the initialization phase
completes. See column subtwophasestate
of pg_subscription
to know the actual two-phase state.
disable_on_error (boolean) #
Specifies whether the subscription should be automatically disabled
if any errors are detected by subscription workers during data
replication from the publisher. The default is
false.
password_required (boolean) #
If set to true, connections to the publisher made
as a result of this subscription must use password authentication
and the password must be specified as a part of the connection
string. This setting is ignored when the subscription is owned by a
superuser. The default is true. Only superusers
can set this value to false.
run_as_owner (boolean) #
If true, all replication actions are performed as the subscription
owner. If false, replication workers will perform actions on each
table as the owner of that table. The latter configuration is
generally much more secure; for details, see
Section 31.9.
The default is false.
origin (string) #
Specifies whether the subscription will request the publisher to only
send changes that don't have an origin or send changes regardless of
origin. Setting origin to none
means that the subscription will request the publisher to only send
changes that don't have an origin. Setting origin
to any means that the publisher sends changes
regardless of their origin. The default is any.
See Notes for details of how
copy_data = true can interact with the
origin parameter.
When specifying a parameter of type boolean, the
= value
part can be omitted, which is equivalent to
specifying TRUE.
See Section 31.9 for details on how to configure access control between the subscription and the publication instance.
When creating a replication slot (the default behavior), CREATE
SUBSCRIPTION cannot be executed inside a transaction block.
Creating a subscription that connects to the same database cluster (for
example, to replicate between databases in the same cluster or to replicate
within the same database) will only succeed if the replication slot is not
created as part of the same command. Otherwise, the CREATE
SUBSCRIPTION call will hang. To make this work, create the
replication slot separately (using the
function pg_create_logical_replication_slot with the
plugin name pgoutput) and create the subscription using
the parameter create_slot = false. See
Section 31.2.3
for examples. This is an implementation restriction that might be lifted in a
future release.
If any table in the publication has a WHERE clause, rows
for which the expression
evaluates to false or null will not be published. If the subscription has
several publications in which the same table has been published with
different WHERE clauses, a row will be published if any
of the expressions (referring to that publish operation) are satisfied. In
the case of different WHERE clauses, if one of the
publications has no WHERE clause (referring to that
publish operation) or the publication is declared as
FOR ALL TABLES
or FOR TABLES IN SCHEMA,
rows are always published regardless of the definition of the other
expressions. If the subscriber is a PostgreSQL
version before 15, then any row filtering is ignored during the initial data
synchronization phase. For this case, the user might want to consider
deleting any initially copied data that would be incompatible with
subsequent filtering. Because initial data synchronization does not take
into account the publication
publish
parameter when copying existing table data, some rows may be copied that
would not be replicated using DML. See
Section 31.2.2 for examples.
Subscriptions having several publications in which the same table has been published with different column lists are not supported.
We allow non-existent publications to be specified so that users can add
those later. This means
pg_subscription
can have non-existent publications.
When using a subscription parameter combination of
copy_data = true and origin = NONE,
the initial sync table data is copied directly from the publisher, meaning
that knowledge of the true origin of that data is not possible. If the
publisher also has subscriptions then the copied table data might have
originated from further upstream. This scenario is detected and a WARNING is
logged to the user, but the warning is only an indication of a potential
problem; it is the user's responsibility to make the necessary checks to
ensure the copied data origins are really as wanted or not.
To find which tables might potentially include non-local origins (due to other subscriptions created on the publisher) try this SQL query:
# substitute <pub-names> below with your publication name(s) to be queried
SELECT DISTINCT PT.schemaname, PT.tablename
FROM pg_publication_tables PT,
pg_subscription_rel PS
JOIN pg_class C ON (C.oid = PS.srrelid)
JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE N.nspname = PT.schemaname AND
C.relname = PT.tablename AND
PT.pubname IN (<pub-names>);
Create a subscription to a remote server that replicates tables in
the publications mypublication and
insert_only and starts replicating immediately on
commit:
CREATE SUBSCRIPTION mysub
CONNECTION 'host=192.168.1.50 port=5432 user=foo dbname=foodb'
PUBLICATION mypublication, insert_only;
Create a subscription to a remote server that replicates tables in
the insert_only publication and does not start replicating
until enabled at a later time.
CREATE SUBSCRIPTION mysub
CONNECTION 'host=192.168.1.50 port=5432 user=foo dbname=foodb'
PUBLICATION insert_only
WITH (enabled = false);
CREATE SUBSCRIPTION is a PostgreSQL
extension.