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Using the Java or the SQL engine

From the Advanced settings of an analysis, you can use either the Java or the SQL engine to execute your analysis. The choice of the engine can sometimes slightly change analysis results, for example when you select the summary statistics indicators to profile a DB2 database. This is because indicators are computed differently depending on the database type, and also because Talend uses special functions when working with Java.

SQL engine

If you use the SQL engine to execute an analysis:

  • An SQL query is generated for each indicator used in the analysis, the analysis runs multiple indicators in parallel and results are refreshed in the charts while the analysis is still in progress.
  • Data monitoring and processing are carried on the DBMS.
  • Only statistical results are retrieved locally.

By using this engine, you guarantee system better performance. You can also access valid/invalid data in the data explorer.

This engine is used by default and is recommended for big data.

Java engine

If you use the Java engine to execute an analysis:

  • Only one query is generated for all indicators used in the analysis.
  • All monitored data is retrieved locally to be analyzed.
  • You can set the parameters to decide whether to access the analyzed data and how many data rows to show per indicator. This will help to avoid memory limitation issues since it is impossible to store all analyzed data.

When you execute the analysis with the Java engine, you do not need different query templates specific for each database. However, system performance is significantly reduced in comparison with the SQL engine. Executing the analysis with the Java engine uses disk space as all data is retrieved and stored locally. If you want to free up some space, you may delete the data stored in the main Talend Studio directory, at Talend-Studio>workspace>project_name>Work_MapDB.

Known limitations on Oracle data types

Some data types are not supported depending on the engine you are using. For more information, see Oracle data types.

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