Top-down Trace of QOpt (cont)
subquery_planner()
- performs algebraic transformations/simplifications, e.g.
- simplifies conditions in where clauses
- converts sub-queries in where to top-level join
- moves having clauses with no aggregate into where
- flattens sub-queries in join list
- simplifies join tree (e.g. removes redundant terms), etc.
- sets up canonical version of query for plan generation
- invokes
grouping_planner() to produce best path
Code in: backend/optimizer/plan/planner.c
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