Research Article
Pipelined XPath Query Based on Cost Optimization
Algorithm 4
CreatePipeline (Ep,
, T).
Input: XPath query expression Ep, XML statistics , number of available worker threads T. | Output: Pipeline represented by pipeline stage sequence . | (1) | ← ExtractPrimitive(Ep); | (2) | ← CostEstimate(, ); | (3) | .size, ;//the number of primitives P; average cost of pipeline stage . | (4) | , ;//cost accumulation ; primitive sequence within a stage . | (5) | if () | (6) | foreach primitive id | (7) | , ; | (8) | if () | (9) | ← CreatePipeStage(), ; | (10) | else | (11) | foreach primitive id | (12) | ← CreatePipeStage(), ; | (13) | AdjustPipeStage(); | (14) | return; |
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