Benedikt Kämpgen: 1 revision: From LD-Cubes

2023-01-04T13:24:17Z

1 revision: From LD-Cubes

Benedikt Kämpgen: /* How to get from MDX to Initial Logical Query Plan */

2014-03-23T13:17:01Z

‎How to get from MDX to Initial Logical Query Plan

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==Interfaces between olap4j and Linked Data Engine in olap4ld==
* Asking a query, schematically:

[[File:Olap4ld_olap_query_sequence_diagram_v2.png]]

===Metadata queries===
* [[Olap4ld Metadata Schema]]

===Analytical queries===

===Overview: Current olap4ld transformation pipeline===
# MDX (SELECT ... ON COLUMNS .. ON ROWS WHERE)
# MDX Parse Tree
# Initial Logical Query Plan

===How to get from MDX to Initial Logical Query Plan===
* Parse Tree is created by olap4j.
** Select node
* From Parse Tree to Initial Query Plan:
** A cellset is created and the metadata from the parse tree retrieved.
*** cube <= Note, here, metadata queries to the cube and its elements are issued via Olap4ldDatabaseMetadata.executeMetadataRequestOnLdce(), e.g., to identify elements in the MDX query and to resolve functions such as Member().
*** COLUMN axis: columnPositions and columnHierarchies
*** ROW axis: rowPositions and rowHierarchies
** An Initial Query Plan from the cellset metadata is created
*** [[BaseCubeOp]] - First, all metadata about the cube is transformed from olap4j metadata to List<Node[]> so that it can be inserted to Base-cube. We could also not have such parameters and have the Base-cube evaluator do that. In my opinion, Base-cube should do more, anyway: Load and validate one single data cube.
*** [[RollupOp]] - Contains all in MDX mentioned dimensions.
*** [[SliceOp]] - Contains all not in MDX mentioned dimensions.
*** [[DiceOp]]
*** [[ProjectionOp]]
*** [[DrillAcrossOp]]

* OLAP cellset (cube, filter, hierarchies, positions, column, hierarchies, positions, row, hier, positions...)
* OLAP query
** OLAP query (cube, slicerrollups, dices, projections)
** Initial Logical Query Plan
* cellset Metadata (MetaData cube, filterAxisMetaData with axis and hierarchies, axisMetaData with axis and hierarchies, filter cell set axis with axis and filter positions, cell set axes with axis and positions)

===CellSets===
[[File:Cellset_schematically.png]]

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Benedikt Kämpgen: 1 revision: From LD-Cubes

Benedikt Kämpgen: /* How to get from MDX to Initial Logical Query Plan */