Metadata

Metadata transform plugin

Description

The Metadata transform plugin is used to extract metadata information from data rows and convert it into regular fields for subsequent processing and analysis.

Core Features:

• Extracts metadata (such as database name, table name, row type, etc.) as visible fields
• Supports custom output field names
• Does not modify original data fields, only adds metadata fields

Typical Use Cases:

• Recording data source (database name, table name) during CDC data synchronization
• Tracking data change types (INSERT, UPDATE, DELETE)
• Recording event time and delay information of data
• Identifying data sources when merging multiple tables

Supported Metadata Fields

Metadata Key	Output Type	Description	Data Source
Database	string	Name of the database containing the data	All connectors
Table	string	Name of the table containing the data	All connectors
RowKind	string	Row change type, values: +I (insert), -U (update before), +U (update after), -D (delete)	All connectors
EventTime	long	Event timestamp of data change (milliseconds)	CDC connectors
Delay	long	Data collection delay time (milliseconds), i.e., the difference between data extraction time and database change time	CDC connectors
Partition	string	Partition information of the data, multiple partition fields separated by commas	Connectors supporting partitions

Important Notes

1. Metadata field names are case-sensitive: Configuration must strictly follow the Key names in the table above (e.g., Database, Table, RowKind, etc.)
2. CDC-specific fields: EventTime and Delay are only valid when using CDC connectors (except TiDB-CDC)

Options

name	type	required	default value	description
metadata_fields	map	no	empty map	Mapping relationship between metadata fields and output fields, format: Metadata Key = output field name

metadata_fields [map]

Defines the mapping relationship between metadata fields and output fields.

Configuration Format:

metadata_fields {
  <Metadata Key> = <output field name>
  <Metadata Key> = <output field name>
  ...
}

Configuration Example:

metadata_fields {
  Database = source_db      # Map database name to source_db field
  Table = source_table      # Map table name to source_table field
  RowKind = op_type         # Map row type to op_type field
  EventTime = event_ts      # Map event time to event_ts field
  Delay = sync_delay        # Map delay time to sync_delay field
  Partition = partition_info # Map partition info to partition_info field
}

Notes:

• The left side must be a supported metadata Key (see table above), and is strictly case-sensitive
• The right side is a custom output field name, which cannot duplicate existing field names
• You can select only the metadata fields you need, not all of them must be configured

Complete Examples

Example 1: MySQL CDC Data Synchronization, Extracting All Metadata

Synchronizing data from MySQL database and extracting all available metadata information.

env {
  parallelism = 1
  job.mode = "STREAMING"
  checkpoint.interval = 5000
}

source {
  MySQL-CDC {
    plugin_output = "mysql_cdc_source"
    server-id = 5652
    username = "root"
    password = "your_password"
    table-names = ["mydb.users"]
    url = "jdbc:mysql://localhost:3306/mydb"
  }
}

transform {
  Metadata {
    plugin_input = "mysql_cdc_source"
    plugin_output = "metadata_added"
    metadata_fields {
      Database = source_database    # Extract database name
      Table = source_table          # Extract table name
      RowKind = change_type         # Extract change type
      EventTime = event_timestamp   # Extract event time
      Delay = sync_delay_ms         # Extract sync delay
    }
  }
}

sink {
  Console {
    plugin_input = "metadata_added"
  }
}

Input Data Example:

Original data row (from mydb.users table):
id=1, name="John", age=25
RowKind: +I (INSERT)

Output Data Example:

Transformed data row:
id=1, name="John", age=25, source_database="mydb", source_table="users",
change_type="+I", event_timestamp=1699000000000, sync_delay_ms=100

---

Example 2: Extracting Only Partial Metadata

Extracting only data source information (database name and table name) for multi-table merge scenarios.

env {
  parallelism = 1
  job.mode = "STREAMING"
}

source {
  MySQL-CDC {
    plugin_output = "multi_table_source"
    server-id = 5652
    username = "root"
    password = "your_password"
    table-names = ["db1.orders", "db2.orders"]
    url = "jdbc:mysql://localhost:3306"
  }
}

transform {
  Metadata {
    plugin_input = "multi_table_source"
    plugin_output = "with_source_info"
    metadata_fields {
      Database = db_name
      Table = table_name
    }
  }
}

sink {
  Jdbc {
    plugin_input = "with_source_info"
    url = "jdbc:mysql://localhost:3306/target_db"
    table = "merged_orders"
    # Target table will contain db_name and table_name fields to identify data source
  }
}