viirya commented on a change in pull request #30245:
URL: https://github.com/apache/spark/pull/30245#discussion_r518584261
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -65,11 +65,46 @@ class EquivalentExpressions {
}
}
+ /**
+ * Adds only expressions which are common in each of given expressions, in a
recursive way.
+ * For example, given two expressions `(a + (b + (c + 1)))` and `(d + (e +
(c + 1)))`,
+ * the common expression `(c + 1)` will be added into `equivalenceMap`.
+ */
+ def addCommonExprs(exprs: Seq[Expression], addFunc: Expression => Boolean =
addExpr): Unit = {
+ var exprSetForAll = ExpressionSet()
+
+ addExprTree(exprs.head, (expr: Expression) => {
+ if (exprSetForAll.contains(expr)) {
+ true
+ } else {
+ exprSetForAll += expr
+ false
+ }
+ })
+
+ exprs.tail.foreach { expr =>
+ var exprSet = ExpressionSet()
+ addExprTree(expr, (expr: Expression) => {
+ if (exprSet.contains(expr)) {
+ true
+ } else {
+ exprSet += expr
+ false
+ }
+ })
+ exprSetForAll = exprSetForAll.intersect(exprSet)
+ }
Review comment:
For expression `head`, we add underlying expressions into
`exprSetForAll` set. But for expressions in `tail`, we keep intersect between
`exprSetForAll` and `exprSet`.
We can merge two blocks, but in the block we need to check if current
expression is head expression and do different logic based on the check.
I prefer current one since it looks simpler.
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