How Magic xpa Prepares the Data View (Magic xpa 4.x)
When Magic xpa starts a task, the engine identifies which records will be included in the Data View Editor before executing operations in the Task Prefix logic units. It does this as follows:
It examines the data view operations, looking for Column operations for variables from main and linked tables, and Virtual operations and parameters, and includes all these variables in the Logical Record and Row.
Magic xpa evaluates the Task Range expression and any Range lower and upper expressions in their order of appearance in the Data View Editor. These Range criteria limit the records that can be included in the data view. If you make Range active during runtime, the end user can further limit the range of records included in the data view. For a data view created from an SQL table, Magic xpa also evaluates and performs the Magic xpa and the database added Where clauses.
If you have entries in the Sort window, the engine sorts the Main Source according to the specified index segments. If you make the Sort function active during runtime, end users can perform their own sorts over the data view record. Only records that comply with the range criteria are sorted.
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The Magic xpa task may be based on a SQL statement defined in the Magic xpa SQL Command task object. In this case, the data view is prepared by the SQL database to which the SQL statement is directed and all the standard Magic xpa data view preparation logic is bypassed. However, Magic xpa maintains normal operation in the stages after the data view preparation stage. The variables used for such a SQL-based data view are usually virtual variables, because the data view is not based on the usual structure that Magic xpa recognizes a data source definition in the Data repository.
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Data View Tuning
Record Data View Instance
Data View Editor
