It seems that you are tackling common scalar expressions (RexNodes) whereas, based on the name the other rule is dealing with common relational expressions (RelNode).
For your rule, consider using RexProgram, RexProgramBuilder, and Calc. They already convert a list of expressions to a DAG, so that no expression is calculated more than once. Julian > On Jul 14, 2022, at 06:31, Jiajun Xie <[email protected]> wrote: > > Hello, all~ > I am writing an RelOptRule that is for CommonSubExpressions. Here is an > example that I completed. > sql: `select sal, sal * 12, sal * 3, sal * 12 + sal * 3 from emp` > planBefore: ```LogicalProject(SAL=[$5], EXPR$1=[*($5, 12)], > EXPR$2=[*($5, 3)], EXPR$3=[+(*($5, 12), *($5, 3))]) > LogicalTableScan(table=[[CATALOG, SALES, EMP]])``` > planAfter: ```LogicalProject(SAL=[$0], EXPR$1=[$1], EXPR$2=[$2], > EXPR$3=[+($1, $2)]) > LogicalProject(SAL=[$5], CSE$0=[*($5, 12)], CSE$1=[*($5, 3)]) > LogicalTableScan(table=[[CATALOG, SALES, EMP]])``` > I found a RelOptRule that is named as CommonRelSubExprRule, but it is > abstract. I wonder if anyone has implemented it? Is it the same as what I > am doing? > Thanks very much~
