MashZone NextGen 10.2 | Appendix | Legacy Presto components | MashZone NextGen Analytics | RAQL Extension to EMML Statements for Mashups | RAQL Extensions to EMML Statements for Streaming | Data Access as Streaming Datasets
 
Data Access as Streaming Datasets
Datasets loaded with the <loadfrom> extension statement always use streaming, making some data available before all results have been received. Streaming also prevents the creation of a document object model (DOM). For examples, see Group and Analyze Rows and Group and Analyze Rows with Row Detail in Getting Started.
Datasets loaded with <directinvoke>, <sql> or <variable> statements also use streaming ifstream = "true". For examples, see A Basic RAQL Query and Getting Started with MashZone NextGen Analytics in Getting Started and Load Data with <sql>.
Query results from a <raql> extension statement also can use streaming to populate the output variable ifstream = "true". For an example, see Use an In-Memory Store to Store and Load Datasets for MashZone NextGen Analytics in Getting Started. Storing datasets to the In-Memory Store with <storeto> also always uses streaming.
There are two critical differences to keep in mind when accessing streamed data in a mashup:
*Streamed data requires RAQL to access the data. Since no DOM exists, the data is not accessible in other EMML statements using XPath.
*The scope for mashup variables that are used to hold streamed data is limited to oneEMML extension statement. Data is streamed to the receiving statement and then discarded.
There are a few ways to handle streamed access when a mashup needs to process a stream in several statements:
*Save the streamed dataset as a document-type variable with a DOM and use the DOM with EMML statements.
*Load the dataset as a stream multiple times in a mashup.
*Separate each process of the dataset stream into different mashups and call these mashups in another mashup.

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