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The service is streaming capable, if the result from the backend storage is delivered to the calling client without storing the complete result in memory. If the core-service is used, the client's request gets transformed to a SQL statement used to query the database. The data the database returns is transformed row by row and sent back to the client. The memory consumption is minimal in this case. If the receiving client is also capable of stream handling the result, even large datasets can be processed.
The search and structure service does do not support stream handling. The complete data set of the backend storage (Elasticsearch) is kept and transformed in memory. Therefore it is mandatory to set an upper limit for the result size. If no size is given, the service enforces a default size.
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