Class TransformFilterPlacementConservative

  • All Implemented Interfaces:
    Transform

    public class TransformFilterPlacementConservative
    extends TransformCopy
    Rewrite an algebra expression to put filters as close to their bound variables in a BGP. Works on (filter (BGP ...) )

    This is a conservative and relatively limited optimization and has been superseded in the default optimizer by the TransformFilterPlacement as of the 2.11.x releases. This original version of TransformFilterPlacement only operates on filters over BGPs, quad blocks, sequences and conditions (a form of LeftJoin with no scope issues) of the same. However in some cases it may be desirable to have the more limited and conservative behaviour so this is preserved in the code for those who want to use this.

    The context flag ARQ.optFilterPlacementConservative may be set to have the default optimizer use this in place of the newer and more aggressive TransformFilterPlacement