Processing Data

Adding Additional Columns

1. On the Process Data page of the real-time synchronization task, click Additional Columns, locate the table to be processed, and click Add in the Operation column.
   Figure 1 Additional columns
   

2. In the displayed Add dialog box, specify the column name, operation type, and field type. Click OK.
   Figure 2 Operation types
   
   

   • In many-to-one mapping scenarios, additional columns for data processing are required to avoid data conflicts.
   • The following operation types are supported:
     • Default: Use the default value to fill in the new column.
     • Use the create_time column and update_time column as an example to fill the new column with the data creation time and data update time.
     • Expression: Use the concat(_current_database, '@',_current_table) expression to fill in the new column. You cannot manually enter an expression.
     • If you fill in the new column in serverName@database@table format, you need to enter a server name and then the database name and table name will be automatically filled in.
     • Value: Select a value, for example, synchronization time.
   • You can apply the additional column information of the first editable table to all editable tables in batches.
   • During MySQL to GaussDB(for MySQL) synchronization, if the number of columns in a single table exceeds 500, the number of additional columns added to the table may exceed the upper limit. As a result, the task fails.
   • If serverName@database@table is used to add an additional column, this additional column will be used on the destination database as an implicit filtering condition for row comparison and value comparison by default.

3. Click Next.

Filtering Data

1. On the Processing Data page, set Processing Type to Data filtering.
   Figure 3 Filtering data
   

2. In the Object area, select the table to be processed.
3. In the Filtering Criteria area, enter the filter criteria (only the part after WHERE in the SQL statement, for example, id=1), and click Verify.
   

   • Each table has only one verification rule.
   • Up to 512 tables can be filtered at a time.
   • The filter expression cannot use the package, function, variable, or constant of a specific DB engine. It must comply with the general SQL standard. Enter the part following WHERE in the SQL statement (excluding WHERE and semicolons), for example, sid > 3 and sname like "G %". A maximum of 512 characters are allowed.
   • In SQL statements for setting filter criteria, keywords must be enclosed in backquotes, and the value of datatime (including date and time) and character string type must be enclosed in single quotation marks, for example, `update` > '2022-07-13 00:00:00' and age >10, `update` ='abc'.
   • Implicit conversion rules are not supported. Enter filtering criteria of a valid data type. For example, if column c of an Oracle database uses characters of the varchar2 type, the filtering criteria must be set to c > '10' instead of c > 10.
   • Filter criteria cannot be configured for large objects, such as CLOB, BLOB, and BYTEA.
   • Filtering rules cannot be set for objects whose database names and table names contain newline characters.
   • The syntax of row-level locks, such as for update, cannot be used as filtering criteria.
   • Function operations cannot be performed on column names. If function operations are performed, data may be inconsistent.
   • You are not advised to set filter criteria for fields of approximate numeric types, such as FLOAT, DECIMAL, and DOUBLE.
   • Do not use fields containing special characters as a filter condition.
   • You are advised not to perform DDL operations on columns involved in filter criteria. Otherwise, task exceptions may occur.
   • You are not advised to use non-idempotent expressions or functions as data processing conditions, such as SYSTIMESTAMP and SYSDATE, because the returned result may be different each time the function is called.
   • The filtering rules for a synchronized table cannot be modified.

4. After the verification is successful, click Generate Processing Rule. The rule is displayed.
5. Click Next.

Advanced Settings for Data Filtering

If you need to query an association table, you can use the advanced settings of data processing.

1. On the Process Data page of the real-time synchronization task, set Processing Type to Data filtering.
2. In the Object area, select the table to be processed.
3. In the Filtering Criteria area, specify the filtering criteria, for example, id1 in (select id from db1.tab1 where id >=3 and id <10), and click Verify.
   

   • Each table has only one verification rule.
   • Up to 512 tables can be filtered at a time.
   • The filter expression cannot use the package, function, variable, or constant of a specific DB engine. It must comply with the general SQL standard. Enter the part following WHERE in the SQL statement (excluding WHERE and semicolons), for example, sid > 3 and sname like "G %". A maximum of 512 characters are allowed.
   • Implicit conversion rules are not supported. Enter filtering criteria of a valid data type. For example, if column c of an Oracle database uses characters of the varchar2 type, the filtering criteria must be set to c > '10' instead of c > 10.
   • Filter criteria cannot be configured for large objects, such as CLOB, BLOB, and BYTEA.
   • Filtering rules cannot be set for objects whose database names and table names contain newline characters.
   • The syntax of row-level locks, such as for update, cannot be used as filtering criteria.
   • You are not advised to set filter criteria for fields of approximate numeric types, such as FLOAT, DECIMAL, and DOUBLE.
   • Do not use fields containing special characters as a filter condition.
   • You are not advised to use non-idempotent expressions or functions as data processing conditions, such as SYSTIMESTAMP and SYSDATE, because the returned result may be different each time the function is called.

4. After the verification is successful, click Generate Processing Rule. The rule is displayed.
5. In the Advanced Settings area, specify the configuration condition and rule for the association table to help you filter data.
   Figure 4 Advanced settings
   
   1. In the Configuration Condition area, enter the association table information entered in 3.

      Database Name, Table Name, Column Name, Primary Key, Index, and Filter Criteria are mandatory. If the table does not have an index, enter its primary key.

      Filter Criteria is the filter condition of the association table information entered in 3.

   2. Then, click Verify.
   3. After the verification is successful, click Generate Configuration Rule. The rule is displayed in the Configuration Rule area.

      To filter data in multiple association tables, repeat 5.

      

      Configuration rules can be deleted.

6. Click Next.

Processing Columns

1. On the Process Data page of the real-time synchronization task, select Processing Columns.
2. In the Object area, select the objects to be processed.
   Figure 5 Processing Columns
   

3. Click Edit to the right of the selected object.
4. In the Edit Column dialog box, select the columns to be mapped and enter new column names.
   Figure 6 Edit Column
   
   

   • You can query or filter columns or create new column names.
   • After the column name is edited, the column name of the destination database is changed to the new name.
   • The new column name cannot be the same as the original column name or an existing column name.
   • Columns whose database names or table names contain newline characters cannot be mapped.
   • The column name in the synchronized table cannot be modified.
   • Only selected columns are synchronized. Newly-added columns are not included in column processing.
   • MySQL to MySQL and MySQL to GaussDB(for MySQL) synchronizations do not support column mapping based on the partitioning column of a partitioned table.
   • GaussDB partition keys cannot be filtered.
   • In the incremental phase, DDL operations cannot be performed on filtered or mapped columns in a table.

5. Click Confirm.
6. Click Next.

Viewing Data Filtering Results

1. On the Data Synchronization Management page, click the task to be processed.
2. Click the Process Data tab to view data filtering records. Click in the upper right corner to refresh the record list.

View Column Processing

1. On the Data Synchronization Management page, click the target synchronization task name in the Task Name/ID column.
2. In the navigation pane on the left, choose Synchronization Mapping. In the upper right corner, and select Columns to view column mapping records. Click in the upper right corner to refresh the record list.
   Figure 7 Viewing column mappings