# CREATE SOURCE: PostgreSQL (New Syntax) Creates a new source from PostgreSQL 11+. > **Disambiguation:** This page reflects the new syntax which allows Materialize to handle upstream DDL changes, specifically adding or dropping columns, without downtime. For the deprecated syntax, see the [old reference page](/sql/create-source/postgres/). Creates a new source from PostgreSQL. Materialize supports creating sources from PostgreSQL version 11+. Once a new source is created, you can CREATE TABLE FROM SOURCE to create the corresponding tables in Materialize and start the data ingestion process. PostgreSQL 16+ is required for connecting Materialize to a physical replica. ## Prerequisites To create a source from PostgreSQL 11+, you must first: - **Configure upstream PostgreSQL instance** - Set up logical replication. - Create a publication. - Create a replication user and password for Materialize to use to connect. - **Configure network security** - Ensure Materialize can connect to your PostgreSQL instance. - **Create a connection to PostgreSQL in Materialize** - The connection setup depends on the network security configuration. For details, see the [PostgreSQL integration guides](/ingest-data/postgres/#integration-guides). ## Syntax To create a source from an external PostgreSQL: ```mzsql CREATE SOURCE [IF NOT EXISTS] [IN CLUSTER ] FROM POSTGRES CONNECTION (PUBLICATION '') [WITH ( [, ...] )] ; ``` | Syntax element | Description | | --- | --- | | **IF NOT EXISTS** | *Optional.* If specified, do not throw an error if a source with the same name already exists. Instead, issue a notice and skip the source creation. | | `` | The name of the source to create. Names for sources must follow the [naming guidelines](/sql/identifiers/#naming-restrictions). | | **IN CLUSTER** `` | *Optional.* The [cluster](/sql/create-cluster) to maintain this source. Otherwise, the source will be created in the active cluster. {{< tip >}} If possible, use a cluster dedicated just for sources. See also [Operational guidelines](/manage/operational-guidelines/#sources). {{< /tip >}} | | `` | The name of the PostgreSQL connection to use for the source. For details on creating connections, check the [`CREATE CONNECTION`](/sql/create-connection/#postgresql) documentation page. A connection is **reusable** across multiple `CREATE SOURCE` statements. | | `` | The name of the PostgreSQL publication to associate with the source. For details on creating a publication in your PostgreSQL database, see the [integration guides for your PostgreSQL](/ingest-data/postgres/#integration-guides). | | **WITH** (`` [, ...]) | *Optional.* The following ``s are supported: \| Option \| Description \| \|--------\|-------------\| \| `TIMESTAMP INTERVAL [=] ` \| The interval at which timestamps are assigned to data read from this source. Accepts positive [interval](/sql/types/interval/) values (e.g. `'500ms'`, `'1s'`). The value must be between the system parameters `min_timestamp_interval` and `max_timestamp_interval`. Default: the value of the `default_timestamp_interval` system parameter (`1s`). The interval can also be changed after creation with [`ALTER SOURCE`](/sql/alter-source/). \| | ## Details ### Ingesting data After a source is created, you can create tables from the source, referencing the tables in the publication, to start ingesting data. You can create multiple tables that reference the same table in the publication. See [`CREATE TABLE FROM SOURCE`](/sql/create-table/) for details. #### Handling table schema changes The use of the `CREATE SOURCE` with the new [`CREATE TABLE FROM SOURCE`](/sql/create-table/) allows for the handling of certain upstream DDL changes without downtime. See [`CREATE TABLE FROM SOURCE`](/sql/create-table/postgres/#handling-table-schema-changes) for details. See also [Handling upstream operations](#handling-upstream-operations) for additional upstream operation considerations. #### Supported types With the new syntax, after a PostgreSQL source is created, you [`CREATE TABLE FROM SOURCE`](/sql/create-table/) to create a corresponding table in Matererialize and start ingesting data.

Materialize natively supports the following PostgreSQL types (including the array type for each of the types):

  • bool
  • bpchar
  • bytea
  • char
  • date
  • daterange
  • float4
  • float8
  • int2
  • int2vector
  • int4
  • int4range
  • int8
  • int8range
  • interval
  • json
  • jsonb
  • numeric
  • numrange
  • oid
  • text
  • time
  • timestamp
  • timestamptz
  • tsrange
  • tstzrange
  • uuid
  • varchar
For more information, including strategies for handling unsupported types, see [`CREATE TABLE FROM SOURCE`](/sql/create-table/). ### Publication membership PostgreSQL's logical replication API does not provide a signal when users remove tables from publications. Because of this, Materialize relies on periodic checks to determine if a table has been removed from a publication, at which time it generates an irrevocable error, preventing any values from being read from the table. However, it is possible to remove a table from a publication and then re-add it before Materialize notices that the table was removed. In this case, Materialize can no longer provide any consistency guarantees about the data we present from the table and, unfortunately, is wholly unaware that this occurred. To mitigate this issue, if you need to drop and re-add a table to a publication, ensure that you remove the table/subsource from the source _before_ re-adding it using the [`DROP SOURCE`](/sql/drop-source/) command. ### PostgreSQL replication slots When you define a source, Materialize will automatically create a **replication slot** in the upstream PostgreSQL database (see [PostgreSQL replication slots](#postgresql-replication-slots)). Each source ingests the raw replication stream data for all tables in the specified publication using **a single** replication slot. This allows you to minimize the performance impact on the upstream database as well as reuse the same source across multiple materializations. The name of the replication slot created by Materialize is prefixed with `materialize_`. In Materialize, you can query the `mz_internal.mz_postgres_sources` to find the replication slots created: ```mzsql SELECT id, replication_slot FROM mz_internal.mz_postgres_sources; ``` ``` id | replication_slot ---------+---------------------------------------------- u8 | materialize_7f8a72d0bf2a4b6e9ebc4e61ba769b71 ``` > **Tip:** - For PostgreSQL 13+, set a reasonable value > for [`max_slot_wal_keep_size`](https://www.postgresql.org/docs/13/runtime-config-replication.html#GUC-MAX-SLOT-WAL-KEEP-SIZE) > to limit the amount of storage used by replication slots. > - If you stop using Materialize, or if either the Materialize instance or > the PostgreSQL instance crash, delete any replication slots. You can query > the `mz_internal.mz_postgres_sources` table to look up the name of the > replication slot created for each source. > - If you delete all objects that depend on a source without also dropping > the source, the upstream replication slot remains and will continue to > accumulate data so that the source can resume in the future. To avoid > unbounded disk space usage, make sure to use [`DROP > SOURCE`](/sql/drop-source/) or manually delete the replication slot. ### Reading from a physical standby Materialize can replicate from a PostgreSQL physical standby (read replica) instead of the primary, using logical decoding on the standby. This requires **PostgreSQL 16+** on both the primary and the standby, since earlier versions do not support creating logical replication slots on a standby. When the upstream is a standby, the replication slot is created on the standby and Materialize only connects to the standby. Note that slot creation on a standby can block until the primary emits a standby snapshot (a `RUNNING_XACTS` WAL record). On an idle primary, run [`SELECT pg_log_standby_snapshot()`](https://www.postgresql.org/docs/16/functions-admin.html#FUNCTIONS-SNAPSHOT-SYNCHRONIZATION) on the primary to unblock source creation. ## Handling upstream operations This section describes how changes to upstream tables that Materialize ingests affect the corresponding Materialize tables. ### Adding a column When you add a new column to your upstream table, Materialize continues to ingest only the existing columns. To incorporate the new column: - If using the new [`CREATE SOURCE` and `CREATE TABLE FROM SOURCE`](/sql/create-source/postgres-v2/) syntax, create a new table from the source. See [Handle upstream column addition](/ingest-data/postgres/source-versioning/#handle-upstream-column-addition). - If using the legacy [`CREATE SOURCE ... FOR ...`](/sql/create-source/postgres/) syntax that creates subsources, use [`DROP SOURCE`](/sql/drop-source/) to drop the affected subsource, and then add the table back to the source using [`ALTER SOURCE ... ADD SUBSOURCE`](/sql/alter-source/). The re-added subsource includes the new column. ### Dropping a column Dropping columns that Materialize does not ingest (for example, columns added after the source was created, or columns that are excluded) is supported. As these columns were never ingested, you can drop them without issue. If your Materialize source ingests a column, dropping that column from your upstream table puts the affected table into an error state. - If using the new [`CREATE SOURCE` and `CREATE TABLE FROM SOURCE`](/sql/create-source/postgres-v2/) syntax, you can safely drop a column by first ignoring it in Materialize. See [Handle upstream column drop](/ingest-data/postgres/source-versioning/#handle-upstream-column-drop). - If using legacy [`CREATE SOURCE ... FOR ...`](/sql/create-source/postgres/) syntax, use [`DROP SOURCE`](/sql/drop-source/) to drop the affected subsource, and then add the table back to the source using [`ALTER SOURCE ... ADD SUBSOURCE`](/sql/alter-source/). ### Changing constraints Materialize ignores the following constraint changes: foreign key, `CHECK`, and `EXCLUSION`. As such, you can add or drop them without affecting ingestion. Materialize also ignores `NOT NULL`, `UNIQUE`, and `PRIMARY KEY` constraints that are added after the Materialize table is created (that is, the table was created without them). Adding such a constraint, and later dropping it, does not affect ingestion. Dropping a `NOT NULL`, `UNIQUE`, or `PRIMARY KEY` constraint that existed when the table was created puts the affected table into an error state. ### Changing a column's data type Changing an ingested column's data type upstream puts the affected Materialize table into an error state unless the column was ingested as `text` via the `TEXT COLUMNS` option. Ingestion for that table stops, and you must drop and recreate the table in Materialize to resume ingestion. ### Renaming a column Renaming a column that Materialize ingests puts the affected table into an error state. Ingestion for that table stops, and you must drop and recreate the table in Materialize to resume ingestion. ### Table-level operations The following upstream operations put the affected table into an error state. Ingestion for that table stops, and you must drop and recreate the affected table in Materialize to resume: - Dropping a table (`DROP TABLE`), removing it from the publication (`ALTER PUBLICATION ... DROP TABLE`), or dropping the publication (`DROP PUBLICATION`). - Renaming a table or moving it to a different schema. - Setting a table's replica identity to anything other than `FULL` (`ALTER TABLE ... REPLICA IDENTITY`). - Truncating a table (`TRUNCATE`). To clear a table without putting it into an error state, use an unqualified `DELETE FROM t;` instead. ## Examples ### Prerequisites To create a source from PostgreSQL 11+, you must first: - **Configure upstream PostgreSQL instance** - Set up logical replication. - Create a publication. - Create a replication user and password for Materialize to use to connect. - **Configure network security** - Ensure Materialize can connect to your PostgreSQL instance. - **Create a connection to PostgreSQL in Materialize** - The connection setup depends on the network security configuration. For details, see the [PostgreSQL integration guides](/ingest-data/postgres/#integration-guides). ### Create a source {#create-source-example} Once you have configured the upstream PostgreSQL, network security, and created the connection, you can create the source. In this example, the PostgreSQL publication is `mz_source` and the connection to PostgreSQL is `pg_connection`. ```mzsql /* This example assumes: - In the upstream PostgreSQL, you have defined: - replication user and password with the appropriate access. - a publication named `mz_source` for the `public.items` and `public.orders` tables. - In Materialize: - You have created a secret for the PostgreSQL password. - You have defined the connection to the upstream PostgreSQL. - You have used the connection to create a source. For example (substitute with your configuration): CREATE SECRET pgpass AS ''; -- substitute CREATE CONNECTION pg_connection TO POSTGRES ( HOST '', -- substitute DATABASE , -- substitute USER , -- substitute PASSWORD SECRET pgpass -- [, ] ); */ CREATE SOURCE pg_source FROM POSTGRES CONNECTION pg_connection ( PUBLICATION 'mz_source' ); ``` After a source is created, you can create tables from the source, referencing specific upstream table(s). Use a [DDL transaction block](/sql/begin/#ddl-only-transactions) to create multiple tables from the same source. ```mzsql BEGIN; CREATE TABLE items FROM SOURCE pg_source(REFERENCE public.items) ; CREATE TABLE orders FROM SOURCE pg_source(REFERENCE public.orders) ; COMMIT; ``` {{< note >}} - Although the example creates the tables with the same name as the upstream tables, the tables in Materialize can have different names. - You can create multiple tables that reference the same upstream table. {{< /note >}} For more information, see [`CREATE TABLE`](/sql/create-table/). ## Related pages - [`CREATE TABLE`](/sql/create-table/) - [`CREATE SECRET`](/sql/create-secret) - [`CREATE CONNECTION`](/sql/create-connection) - [PostgreSQL integration guides](/ingest-data/postgres/#integration-guides) [`enum`]: https://www.postgresql.org/docs/current/datatype-enum.html [`money`]: https://www.postgresql.org/docs/current/datatype-money.html