maropu commented on a change in pull request #29950:
URL: https://github.com/apache/spark/pull/29950#discussion_r502990724
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -216,7 +216,7 @@ abstract class Optimizer(catalogManager: CatalogManager)
// The following batch should be executed after batch "Join Reorder" and
"LocalRelation".
Batch("Check Cartesian Products", Once,
CheckCartesianProducts) :+
- Batch("RewriteSubquery", Once,
+ Batch("RewriteSubquery", fixedPoint,
Review comment:
`FixedPoint(1)` instead? Also, could you leave comments about why we use
it instead of `Once`?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -760,12 +756,43 @@ object CollapseProject extends Rule[LogicalPlan] {
s.copy(child = p2.copy(projectList = buildCleanedProjectList(l1,
p2.projectList)))
}
+ private def collapseProjects(plan: LogicalPlan): LogicalPlan = plan match {
+ case p1 @ Project(_, p2: Project) =>
+ val maxCommonExprs = SQLConf.get.maxCommonExprsInCollapseProject
+
+ if (haveCommonNonDeterministicOutput(p1.projectList, p2.projectList) ||
+ getLargestNumOfCommonOutput(p1.projectList, p2.projectList) >
maxCommonExprs) {
+ p1
+ } else {
+ collapseProjects(
+ p2.copy(projectList = buildCleanedProjectList(p1.projectList,
p2.projectList)))
+ }
+ case _ => plan
+ }
+
private def collectAliases(projectList: Seq[NamedExpression]):
AttributeMap[Alias] = {
AttributeMap(projectList.collect {
case a: Alias => a.toAttribute -> a
})
}
+ // Counts for the largest times common outputs from lower operator are used
in upper operators.
+ private def getLargestNumOfCommonOutput(
Review comment:
we cannot share the code between this and
`moreThanMaxAllowedCommonOutput`?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
##########
@@ -1926,6 +1926,19 @@ object SQLConf {
.booleanConf
.createWithDefault(true)
+ val MAX_COMMON_EXPRS_IN_COLLAPSE_PROJECT =
+ buildConf("spark.sql.optimizer.maxCommonExprsInCollapseProject")
+ .doc("An integer number indicates the maximum allowed number of a common
expression " +
Review comment:
`a common expression` -> `common input attributes`?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
##########
@@ -1926,6 +1926,19 @@ object SQLConf {
.booleanConf
.createWithDefault(true)
+ val MAX_COMMON_EXPRS_IN_COLLAPSE_PROJECT =
+ buildConf("spark.sql.optimizer.maxCommonExprsInCollapseProject")
+ .doc("An integer number indicates the maximum allowed number of a common
expression " +
+ "can be collapsed into upper Project from lower Project by optimizer
rule " +
+ "`CollapseProject`. Normally `CollapseProject` will collapse adjacent
Project " +
+ "and merge expressions. But in some edge cases, expensive expressions
might be " +
+ "duplicated many times in merged Project by this optimization. This
config sets " +
+ "a maximum number. Once an expression is duplicated more than this
number " +
+ "if merging two Project, Spark SQL will skip the merging.")
+ .version("3.1.0")
+ .intConf
Review comment:
Could you add `checkValue`?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
##########
@@ -1926,6 +1926,19 @@ object SQLConf {
.booleanConf
.createWithDefault(true)
+ val MAX_COMMON_EXPRS_IN_COLLAPSE_PROJECT =
+ buildConf("spark.sql.optimizer.maxCommonExprsInCollapseProject")
+ .doc("An integer number indicates the maximum allowed number of a common
expression " +
Review comment:
nit: `the maximum allowed number of a common expression can be collapsed
into upper Project from lower Project ...` => `the maximum allowed number of
common input attributes when collapsing adjacent Projects ...`?
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