CREATE SOURCE: SQL Server

Creates a new source from SQL Server. Materialize supports creating sources from SQL Server version 2016+. 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.

Prerequisites

To create a source from SQL Server (2016+), you must first:

• Configure your SQL Server.

  • Enable Change Data Capture and SNAPSHOT transaction isolation for the database that you would like to replicate.

• Create a connection to SQL Server in Materialize.

  • The connection setup depends on your network security configuration.

Syntax

CREATE SOURCE [IF NOT EXISTS] <src_name>
[IN CLUSTER <cluster_name>]
FROM SQL SERVER CONNECTION <connection_name>
[WITH ( <with_option> [, ...] )]

Ingesting data

After a source is created, you can create tables from the source upstream SQL Server database that have Change Data Capture enabled. You can create multiple tables that reference the same table in the source.

See CREATE TABLE FROM SOURCE for details.

Handling table schema changes

The use of the CREATE SOURCE with the new CREATE TABLE FROM SOURCE allows for the handling of certain upstream DDL changes without downtime.

See Guide: Handle upstream schema changes with zero downtime for details.

See also Handling upstream operations for additional upstream operation considerations.

Supported types

With the new syntax, after a SQL Server source is created, you CREATE TABLE FROM SOURCE to create a corresponding table in Matererialize and start ingesting data.

Materialize natively supports the following SQL Server types:

• tinyint
• smallint
• int
• bigint
• real
• double precision
• float
• bit
• decimal
• numeric
• money
• smallmoney
• char
• nchar
• varchar
• varchar(max)
• nvarchar
• nvarchar(max)
• sysname
• binary
• varbinary
• json
• date
• time
• smalldatetime
• datetime
• datetime2
• datetimeoffset
• uniqueidentifier

char and nchar columns

To preserve values exactly as SQL Server returns them, char and nchar columns are replicated as text rather than fixed-length. SQL Server and Materialize measure fixed-length character types differently, so replicating as text avoids truncation and padding mismatches.

For more information, including strategies for handling unsupported types, see CREATE TABLE FROM SOURCE.

Monitoring source progress

By default, SQL Server sources expose progress metadata as a subsource that you can use to monitor source ingestion progress. The name of the progress subsource can be specified when creating a source using the EXPOSE PROGRESS AS clause; otherwise, it will be named <src_name>_progress.

The following metadata is available for each source as a progress subsource:

And can be queried using:

SELECT lsn
FROM <src_name>_progress;

The reported lsn should increase as Materialize consumes new CDC events from the upstream SQL Server database. For more details on monitoring source ingestion progress and debugging related issues, see Troubleshooting.

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 syntax, create a new table from the source. See Handle upstream column addition.

• If using the legacy CREATE SOURCE ... FOR ... syntax that creates subsources, use DROP SOURCE to drop the affected subsource, and then add the table back to the source using ALTER SOURCE ... ADD SUBSOURCE. 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 syntax, you can safely drop a column by first ignoring it in Materialize. See Handle upstream column drop.

• If using legacy CREATE SOURCE ... FOR ... syntax, use DROP SOURCE to drop the affected subsource, and then add the table back to the source using ALTER SOURCE ... ADD SUBSOURCE.

Changing constraints

Materialize ignores foreign key and CHECK constraint changes. You can add or drop them without affecting ingestion.

Adding a UNIQUE constraint does not affect ingestion. Dropping a UNIQUE constraint puts the affected table into an error state.

SQL Server does not allow dropping a PRIMARY KEY from a table while change data capture is enabled on it. A primary key that existed when Materialize began ingesting the table therefore cannot be dropped upstream.

Adding or removing a NOT NULL constraint on an ingested column requires an upstream ALTER COLUMN, which puts the affected table into an error state. See Changing a column’s data type.

Changing a column’s data type

Any upstream ALTER COLUMN on an ingested column puts the affected Materialize table into an error state. This covers every ALTER COLUMN operation, not just data-type changes. Changing a column’s collation, sparseness, masking, or nullability all error the table the same way. 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.

Removing a capture instance

SQL Server allows up to two capture instances to exist for a table at once. Materialize ingests from one of them.

Removing the capture instance that Materialize is using puts the affected table into an error state. Removing a capture instance that Materialize is not using does not affect 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).
• Renaming a table or moving it to a different schema.

Example

Creating a source

Prerequisite: Creating a connection to SQL Server

First, you must create a connection to your SQL Server database. A connection describes how to connect and authenticate to an external system you want Materialize to read data from.

Once created, a connection is reusable across multiple CREATE SOURCE statements. For more details on creating connections, check the CREATE CONNECTION documentation page.

CREATE SECRET sqlserver_pass AS '<SQL_SERVER_PASSWORD>';

CREATE CONNECTION sqlserver_connection TO SQL SERVER (
    HOST 'instance.foo000.us-west-1.rds.amazonaws.com',
    PORT 1433,
    USER 'materialize',
    PASSWORD SECRET sqlserver_pass,
    DATABASE '<DATABASE_NAME>'
);

If your SQL Server instance is not exposed to the public internet, you can tunnel the connection through and SSH bastion host.

CREATE CONNECTION ssh_connection TO SSH TUNNEL (
    HOST 'bastion-host',
    PORT 22,
    USER 'materialize',
    DATABASE '<DATABASE_NAME>'
);

CREATE CONNECTION sqlserver_connection TO SQL SERVER (
    HOST 'instance.foo000.us-west-1.rds.amazonaws.com',
    SSH TUNNEL ssh_connection,
    DATABASE '<DATABASE_NAME>'
);

Creating the source in Materialize

You must enable Change Data Capture. See the setup instructions for Azure SQL Database or self-hosted SQL Server.

Once CDC is enabled for all of the tables you wish to create subsources for, you can create a SOURCE in Materialize to begin replicating data!

Create source from the connection we just created

CREATE SOURCE mz_source
    FROM SQL SERVER CONNECTION sqlserver_connection;

After a source is created, you can create a table from the source, referencing specific table(s).

Creates a table in Materialize from the upstream table dbo.items

CREATE TABLE items FROM SOURCE mz_source(REFERENCE dbo.items);

Related pages

• CREATE SECRET
• CREATE CONNECTION
• CREATE SOURCE