PostgreSQL CDC

PostgreSQL CDC source connector

Key features​

• batch

• stream

• exactly-once

• column projection

• parallelism

• support user-defined split

Description​

The Postgre CDC connector allows for reading snapshot data and incremental data from Postgre database. This document describes how to set up the Postgre CDC connector to run SQL queries against Postgre databases.

Supported DataSource Info​

Datasource	Supported versions	Driver	Url
PostgreSQL	Different dependency version has different driver class.	org.postgresql.Driver	jdbc:postgresql://localhost:5432/test
PostgreSQL	If you want to manipulate the GEOMETRY type in PostgreSQL.	org.postgresql.Driver	jdbc:postgresql://localhost:5432/test

Using Dependency​

Here are the steps to enable CDC (Change Data Capture) in PostgreSQL:

1. Ensure the wal_level is set to logical: Modify the postgresql.conf configuration file by adding "wal_level = logical", restart the PostgreSQL server for the changes to take effect. Alternatively, you can use SQL commands to modify the configuration directly:

ALTER SYSTEM SET wal_level TO 'logical';
SELECT pg_reload_conf();

1. Change the REPLICA policy of the specified table to FULL

ALTER TABLE your_table_name REPLICA IDENTITY FULL;

Data Type Mapping​

PostgreSQL Data type	Nexus Data type
BOOL	BOOLEAN
_BOOL	ARRAY<BOOLEAN>
BYTEA	BYTES
_BYTEA	ARRAY<TINYINT>
INT2 SMALLSERIAL INT4 SERIAL	INT
_INT2 _INT4	ARRAY<INT>
INT8 BIGSERIAL	BIGINT
_INT8	ARRAY<BIGINT>
FLOAT4	FLOAT
_FLOAT4	ARRAY<FLOAT>
FLOAT8	DOUBLE
_FLOAT8	ARRAY<DOUBLE>
NUMERIC(Get the designated column's specified column size>0)	DECIMAL(Get the designated column's specified column size,Gets the number of digits in the specified column to the right of the decimal point)
NUMERIC(Get the designated column's specified column size<0)	DECIMAL(38, 18)
BPCHAR CHARACTER VARCHAR TEXT GEOMETRY GEOGRAPHY JSON JSONB	STRING
_BPCHAR _CHARACTER _VARCHAR _TEXT	ARRAY<STRING>
TIMESTAMP	TIMESTAMP
TIME	TIME
DATE	DATE
OTHER DATA TYPES	NOT SUPPORTED YET

Source Options​

Name	Type	Required	Default	Description
base-url	String	Yes	-	The URL of the JDBC connection. Refer to a case: jdbc:postgresql://localhost:5432/postgres_cdc?loggerLevel=OFF.
username	String	Yes	-	Name of the database to use when connecting to the database server.
password	String	Yes	-	Password to use when connecting to the database server.
database-names	List	No	-	Database name of the database to monitor.
table-names	List	Yes	-	Table name of the database to monitor. The table name needs to include the database name, for example: database_name.table_name
table-names-config	List	No	-	Table config list. for example: [{"table": "db1.schema1.table1","primaryKeys":["key1"]}]
startup.mode	Enum	No	INITIAL	Optional startup mode for PostgreSQL CDC consumer, valid enumerations are initial, earliest, latest and specific. initial: Synchronize historical data at startup, and then synchronize incremental data. earliest: Startup from the earliest offset possible. latest: Startup from the latest offset. specific: Startup from user-supplied specific offsets.
snapshot.split.size	Integer	No	8096	The split size (number of rows) of table snapshot, captured tables are split into multiple splits when read the snapshot of table.
snapshot.fetch.size	Integer	No	1024	The maximum fetch size for per poll when read table snapshot.
slot.name	String	No	-	The name of the PostgreSQL logical decoding slot that was created for streaming changes from a particular plug-in for a particular database/schema. The server uses this slot to stream events to the connector that you are configuring. Default is Nexus.
decoding.plugin.name	String	No	pgoutput	The name of the Postgres logical decoding plug-in installed on the server,Supported values are decoderbufs, wal2json, wal2json_rds, wal2json_streaming,wal2json_rds_streaming and pgoutput.
server-time-zone	String	No	UTC	The session time zone in database server. If not set, then ZoneId.systemDefault() is used to determine the server time zone.
connect.timeout.ms	Duration	No	30000	The maximum time that the connector should wait after trying to connect to the database server before timing out.
connect.max-retries	Integer	No	3	The max retry times that the connector should retry to build database server connection.
connection.pool.size	Integer	No	20	The jdbc connection pool size.
chunk-key.even-distribution.factor.upper-bound	Double	No	100	The upper bound of the chunk key distribution factor. This factor is used to determine whether the table data is evenly distributed. If the distribution factor is calculated to be less than or equal to this upper bound (i.e., (MAX(id) - MIN(id) + 1) / row count), the table chunks would be optimized for even distribution. Otherwise, if the distribution factor is greater, the table will be considered as unevenly distributed and the sampling-based sharding strategy will be used if the estimated shard count exceeds the value specified by sample-sharding.threshold. The default value is 100.0.
chunk-key.even-distribution.factor.lower-bound	Double	No	0.05	The lower bound of the chunk key distribution factor. This factor is used to determine whether the table data is evenly distributed. If the distribution factor is calculated to be greater than or equal to this lower bound (i.e., (MAX(id) - MIN(id) + 1) / row count), the table chunks would be optimized for even distribution. Otherwise, if the distribution factor is less, the table will be considered as unevenly distributed and the sampling-based sharding strategy will be used if the estimated shard count exceeds the value specified by sample-sharding.threshold. The default value is 0.05.
sample-sharding.threshold	Integer	No	1000	This configuration specifies the threshold of estimated shard count to trigger the sample sharding strategy. When the distribution factor is outside the bounds specified by chunk-key.even-distribution.factor.upper-bound and chunk-key.even-distribution.factor.lower-bound, and the estimated shard count (calculated as approximate row count / chunk size) exceeds this threshold, the sample sharding strategy will be used. This can help to handle large datasets more efficiently. The default value is 1000 shards.
inverse-sampling.rate	Integer	No	1000	The inverse of the sampling rate used in the sample sharding strategy. For example, if this value is set to 1000, it means a 1/1000 sampling rate is applied during the sampling process. This option provides flexibility in controlling the granularity of the sampling, thus affecting the final number of shards. It's especially useful when dealing with very large datasets where a lower sampling rate is preferred. The default value is 1000.
exactly_once	Boolean	No	false	Enable exactly once semantic.
format	Enum	No	DEFAULT	Optional output format for PostgreSQL CDC, valid enumerations are DEFAULT, COMPATIBLE_DEBEZIUM_JSON.
debezium	Config	No	-	Pass-through Debezium's properties to Debezium Embedded Engine which is used to capture data changes from PostgreSQL server.
common-options		no	-	Source plugin common parameters, please refer to Source Common Options for details

Task Example​

Simple​

Support multi-table reading

env {
  # You can set engine configuration here
  execution.parallelism = 1
  job.mode = "STREAMING"
  checkpoint.interval = 5000
  read_limit.bytes_per_second=7000000
  read_limit.rows_per_second=400
}

source {
  Postgres-CDC {
    result_table_name = "customers_Postgre_cdc"
    username = "postgres"
    password = "postgres"
    database-names = ["postgres_cdc"]
    schema-names = ["inventory"]
    table-names = ["postgres_cdc.inventory.postgres_cdc_table_1,postgres_cdc.inventory.postgres_cdc_table_2"]
    base-url = "jdbc:postgresql://postgres_cdc_e2e:5432/postgres_cdc?loggerLevel=OFF"
  }
}

transform {

}

sink {
  jdbc {
    source_table_name = "customers_Postgre_cdc"
    url = "jdbc:postgresql://postgres_cdc_e2e:5432/postgres_cdc?loggerLevel=OFF"
    driver = "org.postgresql.Driver"
    user = "postgres"
    password = "postgres"

    generate_sink_sql = true
    # You need to configure both database and table
    database = postgres_cdc
    chema = "inventory"
    tablePrefix = "sink_"
    primary_keys = ["id"]
  }
}

Support custom primary key for table​

source {
  Postgres-CDC {
    result_table_name = "customers_mysql_cdc"
    username = "postgres"
    password = "postgres"
    database-names = ["postgres_cdc"]
    schema-names = ["inventory"]
    table-names = ["postgres_cdc.inventory.full_types_no_primary_key"]
    base-url = "jdbc:postgresql://postgres_cdc_e2e:5432/postgres_cdc?loggerLevel=OFF"
    decoding.plugin.name = "decoderbufs"
    exactly_once = false
    table-names-config = [
      {
        table = "postgres_cdc.inventory.full_types_no_primary_key"
        primaryKeys = ["id"]
      }
    ]
  }
}