maropu commented on a change in pull request #25717: [WIP][SPARK-29013][SQL]
Structurally equivalent subexpression elimination
URL: https://github.com/apache/spark/pull/25717#discussion_r321999396
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
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@@ -65,35 +89,102 @@ class EquivalentExpressions {
}
/**
- * Adds the expression to this data structure recursively. Stops if a
matching expression
- * is found. That is, if `expr` has already been added, its children are not
added.
+ * Adds each expression to structural expression data structure, grouping
them with existing
+ * structurally equivalent expressions. Non-recursive.
+ */
+ def addStructExpr(ctx: CodegenContext, expr: Expression): Unit = {
+ if (expr.deterministic) {
+ val refs = expr.collect {
+ case b: BoundReference => b
+ }
+
+ // For structural equivalent expressions, we need to pass in int type
ordinals into
+ // split functions. If the number of ordinals is more than JVM function
limit, we skip
+ // this expression.
+ // We calculate function parameter length by the number of ints plus
`INPUT_ROW` plus
+ // a int type result array index.
+ val parameterLength = CodeGenerator.calculateParamLength(refs.map(_ =>
Literal(0))) + 2
+ if (CodeGenerator.isValidParamLength(parameterLength)) {
Review comment:
If the length goes over the limit, the current logic gives up eliminating
common exprs? If so, can we fall back into the non-structural mode?
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