Greenplum Migration Synchronization to PostgreSQL

NineData data replication supports copying data from Greenplum to PostgreSQL, supporting both structural and full data replication.

Feature Introduction

NineData data replication supports high-performance replication of structure, full data, and incremental data between data sources. For certain data sources, it also provides bidirectional replication, enabling the quick construction of geo-distributed active-active business architectures.

• Structure: Supports the replication of object structures between homogeneous and heterogeneous data sources, greatly reducing the barrier to data replication between two sources.
• Full Data: Achieves row-level concurrent batch replication through intelligent data sharding, effectively ensuring replication performance. The independently developed novel breakpoint resume technology ensures the accuracy of data in tables without primary keys.
• Incremental Data: Supports DML and DDL incremental data replication for all object types. By leveraging technologies such as row-level concurrency and hotspot merging, it delivers robust replication performance.
• Bidirectional Real-time Data Replication (only between MySQL instances): Direct bidirectional replication of data between multiple nodes ensures that all node data remains up-to-date.

With the above features, it is easy and efficient to achieve scenarios such as full|incremental data replication, full|incremental data migration, full|incremental data synchronization, data integration, and seamless migration without downtime, providing enterprises with flexible and reliable data replication solutions.

Prerequisites

• The source and target data sources have been added to NineData. For details on how to add them, see Adding Data Sources.

• The source database type is Greenplum.

• The target database is PostgreSQL.

• The following permissions for the source and target data sources are required.

  Replication Type	Source Data Source	Target Data Source
  Structural Replication	SELECT、SHOW VIEW	DDL
  Full Replication	SELECT、SHOW VIEW	DML

Usage Limitations

• Before performing data synchronization, it is necessary to assess the performance of the source and target data sources, and it is recommended to perform data synchronization during off-peak business hours. Otherwise, the initial full data will occupy a certain amount of read and write resources of the source and target data sources, leading to increased database load.
• It is recommended to ensure that each table in the synchronization object has a primary key or unique constraint, and the column names are unique, otherwise, the same data may be synchronized repeatedly.

Operation Steps

Commercialization Notice

NineData’s data replication product has been commercialized. You can still use 10 replication tasks for free, with the following considerations:

• Among the 10 replication tasks, you can include 1 Incremental task, with a specification of Micro.

• Tasks with a status of Terminated do not count towards the 10-task limit. If you have already created 10 replication tasks and want to create more, you can terminate previous replication tasks and then create new ones.

• When creating replication tasks, you can only select the Spec you have purchased. Specifications that have not been purchased will be grayed out and cannot be selected. If you need to purchase additional specifications, please contact us through the customer service icon at the bottom right of the page.

1. Log in to the NineData Console.

2. In the left navigation pane, click Replication > Data Replication.

3. On the Replication page, click Create Replication in the upper-right corner.

4. On the Source & Target tab, configure the parameters in the following table, and click Next.

   Parameter	Description
   Name	Enter a name for the data synchronization task. To make the task easier to find and manage later, use a meaningful name. Up to 64 characters are supported.
   Source	The data source that contains the objects to synchronize.
   Target	The data source that receives the synchronized objects.
   Target Object Name	Select the case conversion rule for object names after they are migrated from the source to the target. Convert all to Lowercase: Regardless of the naming rule on the source, all target names are lowercase. Consistent with Source: Keep the naming rule of the source. Convert all to Uppercase: Regardless of the naming rule on the source, all target names are uppercase.
   Type	Select the replication type. Schema: Synchronize only the database and table schemas of the source data source, without synchronizing data. Full: Synchronize all objects and data from the source data source, namely full data replication. The switch on the right enables periodic full replication. For more information, see Periodic Full Replication.
   Spec (Unavailable only when Schema is selected)	The specification of the replication task. A larger specification provides a higher replication rate. Hover over the icon to view the rate and configuration information of each specification. Each specification shows the available quantity and total quantity. When the available quantity is 0, the specification is grayed out and cannot be selected.
   If target table already exists (Required when Schema is selected)	Pre-Check Error and Stop Task: Stop the task when a table with the same name is detected during the precheck stage. Skip and Continue Task: When a table with the same name is detected during the precheck stage, display a prompt and continue the task. During schema replication, ignore the table with the same name. If you also perform data replication, data is appended to the table with the same name and existing data is not overwritten. Delete Objects and Rewrite: When a table with the same name is detected during the precheck stage, display a prompt and continue the task. During schema replication, delete the table with the same name in the target database and replicate the table schema again based on the source database. If you also perform data replication, data is written after schema replication is complete.
   Target Table Exists Data (Required when Full is selected)	Pre-Check Error and Stop Task: Stop the task when data is detected in the target table during the precheck stage. Ignore existing target data and append to it.: When data is detected in the target table during the precheck stage, ignore that data and append other data. Clear target existing data before write: When data is detected in the target table during the precheck stage, delete that data and write it again.

5. On the Objects tab, configure the following parameters, and click Next.

   Parameter	Description
   Replication Objects	Select the content to replicate. You can select All Objects to replicate all content in the source database, or select Customized Object, select the content to replicate in the Source Object list, and click > to add it to the Target Object list on the right.

   If you need to create multiple replication links with the same replication objects, you can create a configuration file and import it when creating a task. Click Import Config in the upper-right corner, click Download Template to download the configuration file template, edit the file, and then click Upload to upload it for batch import. Configuration file description:

   Parameter	Description
   source_table_name	The source table name of the object to synchronize.
   destination_table_name	The target table name that receives the synchronized object.
   source_schema_name	The source schema name of the object to synchronize.
   destination_schema_name	The target schema name that receives the synchronized object.
   source_database_name	The source database name of the object to synchronize.
   target_database_name	The target database name that receives the synchronized object.
   column_list	The list of columns to synchronize.
   extra_configuration	Additional configuration information. You can configure the following information here: column_rules: Defines column mappings and value rules. Field descriptions: column_name: Original column name. destination_column_name: Specifies the target column name. column_value: Specifies the column value, which can be an SQL function or a constant value. filter_condition: Specifies row-level data filtering conditions. Only rows that meet the conditions are replicated.

   tip

   • The following is an example of extra_configuration:

     {
       "extra_config":{
         "column_rules":[
           {
             "column_name": "created_time", // Specifies the original column name to be mapped.
             "destination_column_name": "migrated_time", // Maps the target column name to "migrated_time".
             "column_value": "current_timestamp()" // Changes the column value to the current timestamp.
           }
         ],
         "filter_condition": "id != 0" // Only rows whose ID is not 0 are synchronized.
       }
     }

   • For a complete example of the configuration file, see the downloaded template.

6. On the "Mapping" tab, choose different operations based on the selected replication type, and click Save and Pre-Check. If the source and target data sources are updated during mapping configuration, click Refresh Metadata in the upper-right corner of the page to refresh the source and target data source information.

   • Includes Schema: Configure the table name after synchronization to the target data source.

   • Does not include Schema: The system selects the database with the same name in the target data source by default. If no such database exists, you need to manually select the target database. The table names and column names in the target database must match the synchronization objects. If they do not match, you can manually map the table names and column names.

   You can also perform the following operations:

   • Click Mapping & Filtering on the right side of the page to customize the column names after synchronization to the target data source.
   • On the Mapping & Filtering page, click Data Filter to configure filtering conditions by using comparison expressions. Only data that meets the filtering conditions is synchronized to the target data source. For example, if the filtering condition is set to emp_no>=10005, data whose emp_no column value is less than 10005 is not synchronized to the target data source.
   • Click the icon to the right of "Target Table" to search for a table name and replace it with the target name.
   • Enter a table name in the Search Table text box in the upper-right corner to quickly locate the target table.
   • Click Batch Configuration in the upper-right corner to define common rules in batches, such as table name and column name case conversion, prefix or suffix addition, and replacement, so that mapping configuration can be applied uniformly to a large number of tables and columns.

• Click the drop-down menu to the right of Object Owner to specify the owner of the object. If you do not select an owner, An account with the same name as schema is used by default.

7. On the Pre-check tab, wait for the system to complete the precheck. After the precheck is passed, click Launch.

   • You can select Enable data consistency comparison. After the synchronization task is complete, a data consistency comparison task based on the source data source automatically starts to ensure data consistency between both ends. Based on the selected Type, Enable data consistency comparison starts at the following times:

     • Schema: Starts after schema replication is complete.
     • Schema+Full: Starts after full replication is complete.
     • Full: Starts after full replication is complete.

   • If the precheck fails, click Details in the Actions column on the right of the failed check item, troubleshoot the cause, manually fix the issue, and then click Check Again to run the precheck again until it passes.

   • Check items whose Result is Warning can be fixed or ignored depending on the situation.

8. On the Launch page, the Launch Successfully prompt appears, indicating that the synchronization task has started. You can then perform the following operations:

   • Click View Details to view the execution status of each stage of the synchronization task.

   • Click Back to list to return to the Replication task list page.

Viewing Synchronization Results

1. Log in to the NineData Console.

2. Click on Replication > Data Replication in the left navigation pane.

3. On the Replication page, click on the Task ID of the target synchronization task, and the page description is as follows.

   

   Number	Function	Description
   1	Configure Alerts	After configuring alerts, the system will notify you in the selected way when the task fails. For more information, please refer to Operational Monitoring Overview.
   2	More	Pause: Pause the task. Only tasks with the status Running are selectable. Duplicate: Create a new replication task with the same configuration as the current task. Terminate: End tasks that are incomplete or in listening (i.e., in incremental synchronization). After terminating the task, it cannot be restarted, so please proceed with caution. If triggers are included in the synchronization object, trigger replication options will pop up, please choose as needed. Delete: Delete the task. Once the task is deleted, it cannot be recovered, so please proceed with caution.
   3	Structural Replication (Displayed in scenarios involving structural replication)	Display the progress and details of structural replication. Click on Log on the right side of the page: View the execution log of structural replication. Click on on the right side of the page: View the latest information. Click on View DDL in the Actions column on the right side of the target object in the list: View SQL playback.
   4	Full Replication (Displayed in scenarios involving full replication)	Display the progress and details of full replication. Click on Monitor on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click on Flow Control Settings on the right side of the monitoring indicator page to limit the rate of data written to the target data source per second. The unit is rows/second. Click on Log on the right side of the page: View the execution log of full replication. Click on on the right side of the page: View the latest information.
   5	Data Comparison	Display the comparison results between the source data source and the target data source. If you have not enabled data comparison, click Enable Comparison on the page. Click on Re-compare on the right side of the page: Re-initiate the comparison of data between the current source and target ends. Click on Stop on the right side of the page: After starting the comparison task, you can click this button to stop the comparison task immediately. Click on Log on the right side of the page: View the execution log of consistency comparison. Click on Monitor (only displayed in data comparison): View the trend chart of RPS (records per second compared) for comparison. Click on Details to view records from earlier times. Click on in the Actions column on the right side of the comparison list (displayed only under the Data tab when there is inconsistency): View detailed comparison between the source and target ends. Click on in the Actions column on the right side of the comparison list (displayed only in case of inconsistency): Generate change SQL, which you can directly copy to the target data source to execute and modify the inconsistent content.
   6	Expand	Display detailed information of the current replication task. Common Options: Export table configuration: Export the current task's database and table configuration, allowing for quick import when creating a new replication task. This helps rapidly establish multiple replication links with the same replication objects. Alert Rules: Configure the alarm strategy for the current task.

Appendix 1: Data Type Mapping Table

Category	Greenplum Data Type	PostgreSQL Data Type
Numeric	SMALLINT/INT2	SMALLINT/INT2
	INTEGER/INT4/INT	INTEGER/INT4/INT
	BIGINT/INT8	BIGINT/INT8
	BIT	BIT
	BIT VARING	BIT VARING
	DOUBLE	DOUBLE
	DOUBLE PRECISION	DOUBLE PRECISION
	REAL	REAL
	FLOAT4	FLOAT4
	FLOAT8	FLOAT8
	NUMERIC	NUMERIC
	MOENY	MOENY
	BOOL/BOOLEAN	BOOL/BOOLEAN
DATE AND TIME	DATE	DATE
	TIMESTAMP WITHOUT TIME ZONE /TIMESTAMPTZ	TIMESTAMP WITHOUT TIME ZONE /TIMESTAMPTZ
	TIMESTAMP WITH TIME ZONE	TIMESTAMP WITH TIME ZONE
	TIME WITH TIME ZONE /TIMETZ	TIME WITH TIME ZONE /TIMETZ
	TIMESTAMP	TIMESTAMP
	TIME	TIME
	INTERVAL	INTERVAL
STRING	CHAR	CHAR
	CHARACTER VARYING	CHARACTER VARYING
	CHARACTER	CHARACTER
	TEXT	TEXT
	INET	INET
	CIDR	CIDR
	MACADDR	MACADDR
	MACADDR8	MACADDR8
	UUID	UUID
RANGE	INT4RANGE	INT4RANGE
	INT8RANGE	INT8RANGE
	NUMRANGE	NUMRANGE
	DATERANGE	DATERANGE
JSON	JSON	JSON
	JSONB	JSONB
BINARY	BYTEA	BYTEA
SPATIAL	POINT	POINT
	LINE	LINE
	LSEG	LSEG
	BOX	BOX
	PATH	PATH
	POLYGON	POLYGON
	CIRCLE	CIRCLE
XML	XML	XML

Appendix 2: Pre-Check Item List

Check Item	Check Content
Source Data Source Connection Check	Check the gateway status of the source data source, whether the instance is reachable, and the accuracy of the username and password
Target Data Source Connection Check	Check the gateway status of the target data source, whether the instance is reachable, and the accuracy of the username and password
Source Database Permission Check	Check whether the account permissions of the source database meet the requirements
Target Database Data Existence Check	Check whether there is data in the target database for the objects to be replicated
Target Database Same Name Object Existence Check	Check whether the objects to be replicated already exist in the target database

Related Documentation

Introduction to Data Replication