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new bbeb8d7417ba [SPARK-46640][SQL] Fix RemoveRedundantAlias by excluding
subquery attributes
bbeb8d7417ba is described below
commit bbeb8d7417bafa09ad5202347175a47b3217e27f
Author: Nikhil Sheoran <125331115+nikhilsheoran...@users.noreply.github.com>
AuthorDate: Fri Jan 12 10:20:49 2024 +0800
[SPARK-46640][SQL] Fix RemoveRedundantAlias by excluding subquery attributes
### What changes were proposed in this pull request?
- In `RemoveRedundantAliases`, we have an `excluded` AttributeSet argument
denoting the references for which we should not remove aliases. For a query
with subquery expressions, adding the attributes references by the subquery in
the `excluded` set prevents rewrites that might remove presumedly redundant
aliases. (Changes in RemoveRedundantAlias)
- Added a configuration flag to disable this fix, if not needed.
- Added a unit test with Filter exists subquery expression to show how the
alias would have been removed.
### Why are the changes needed?
- `RemoveRedundantAliases` does not take into account the outer attributes
of a `SubqueryExpression` when considering redundant aliases, potentially
removing them if it thinks they are redundant.
- This can cause scenarios where a subquery expression has conditions like
`a#x = a#x` i.e. both the attribute names and the expression ID(s) are the
same. This can then lead to conflicting expression ID(s) error.
- For example, in the query example below, the `RemoveRedundantAliases`
would remove the alias `a#0 as a#1` and replace `a#1` with `a#0` in the Filter
exists subquery expression which would create an issue if the subquery
expression had an attribute with reference `a#0` (possible due to different
scan relation instances possibly having the same attribute ID(s) (Ref: #40662)
```
Filter exists [a#1 && (a#1 = b#2)]
: +- LocalRelation <empty>, [b#2]
+- Project [a#0 AS a#1]
+- LocalRelation <empty>, [a#0]
```
becomes
```
Filter exists [a#0 && (a#0 = b#2)]
: +- LocalRelation <empty>, [b#2]
+- LocalRelation <empty>, [a#0]
```
- The changes are needed to fix this bug.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
- Added a unit test with Filter exists subquery expression to show how the
alias would have been removed.
### Was this patch authored or co-authored using generative AI tooling?
No
Closes #44645 from nikhilsheoran-db/SPARK-46640.
Authored-by: Nikhil Sheoran
<125331115+nikhilsheoran...@users.noreply.github.com>
Signed-off-by: Wenchen Fan <wenc...@databricks.com>
---
.../spark/sql/catalyst/optimizer/Optimizer.scala | 12 +++++-
.../org/apache/spark/sql/internal/SQLConf.scala | 9 ++++
.../RemoveRedundantAliasAndProjectSuite.scala | 48 ++++++++++++++++++++++
3 files changed, 68 insertions(+), 1 deletion(-)
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index 61791b35df85..8fcc7c7c26b4 100644
---
a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++
b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -584,10 +584,20 @@ object RemoveRedundantAliases extends Rule[LogicalPlan] {
}
case _ =>
+ val subQueryAttributes = if (conf.getConf(SQLConf
+ .EXCLUDE_SUBQUERY_EXP_REFS_FROM_REMOVE_REDUNDANT_ALIASES)) {
+ // Collect the references for all the subquery expressions in the
plan.
+ AttributeSet.fromAttributeSets(plan.expressions.collect {
+ case e: SubqueryExpression => e.references
+ })
+ } else {
+ AttributeSet.empty
+ }
+
// Remove redundant aliases in the subtree(s).
val currentNextAttrPairs = mutable.Buffer.empty[(Attribute, Attribute)]
val newNode = plan.mapChildren { child =>
- val newChild = removeRedundantAliases(child, excluded)
+ val newChild = removeRedundantAliases(child, excluded ++
subQueryAttributes)
currentNextAttrPairs ++= createAttributeMapping(child, newChild)
newChild
}
diff --git
a/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
b/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
index 1928e74363cb..743a2e20c885 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
@@ -4513,6 +4513,15 @@ object SQLConf {
.booleanConf
.createWithDefault(true)
+ val EXCLUDE_SUBQUERY_EXP_REFS_FROM_REMOVE_REDUNDANT_ALIASES =
+
buildConf("spark.sql.optimizer.excludeSubqueryRefsFromRemoveRedundantAliases.enabled")
+ .internal()
+ .doc("When true, exclude the references from the subquery expressions
(in, exists, etc.) " +
+ s"while removing redundant aliases.")
+ .version("4.0.0")
+ .booleanConf
+ .createWithDefault(true)
+
val TIME_TRAVEL_TIMESTAMP_KEY =
buildConf("spark.sql.timeTravelTimestampKey")
.doc("The option name to specify the time travel timestamp when reading
a table.")
diff --git
a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RemoveRedundantAliasAndProjectSuite.scala
b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RemoveRedundantAliasAndProjectSuite.scala
index cd19e5062ae1..8a0a0466ca74 100644
---
a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RemoveRedundantAliasAndProjectSuite.scala
+++
b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RemoveRedundantAliasAndProjectSuite.scala
@@ -23,6 +23,7 @@ import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.plans.PlanTest
import org.apache.spark.sql.catalyst.plans.logical._
import org.apache.spark.sql.catalyst.rules._
+import org.apache.spark.sql.internal.SQLConf
import org.apache.spark.sql.types.MetadataBuilder
class RemoveRedundantAliasAndProjectSuite extends PlanTest {
@@ -130,4 +131,51 @@ class RemoveRedundantAliasAndProjectSuite extends PlanTest
{
correlated = false)
comparePlans(optimized, expected)
}
+
+ test("SPARK-46640: do not remove outer references from a subquery
expression") {
+ val a = $"a".int
+ val a_alias = Alias(a, "a")()
+ val a_alias_attr = a_alias.toAttribute
+ val b = $"b".int
+
+ // The original input query
+ // Filter exists [a#1 && (a#1 = b#2)]
+ // : +- LocalRelation <empty>, [b#2]
+ // +- Project [a#0 AS a#1]
+ // +- LocalRelation <empty>, [a#0]
+ val query = Filter(
+ Exists(
+ LocalRelation(b),
+ outerAttrs = Seq(a_alias_attr),
+ joinCond = Seq(EqualTo(a_alias_attr, b))
+ ),
+ Project(Seq(a_alias), LocalRelation(a))
+ )
+
+ // The alias would not be removed if excluding subquery references is
enabled.
+ val expectedWhenExcluded = query
+
+ // The alias would have been removed if excluding subquery references is
disabled.
+ // Filter exists [a#0 && (a#0 = b#2)]
+ // : +- LocalRelation <empty>, [b#2]
+ // +- LocalRelation <empty>, [a#0]
+ val expectedWhenNotExcluded = Filter(
+ Exists(
+ LocalRelation(b),
+ outerAttrs = Seq(a),
+ joinCond = Seq(EqualTo(a, b))
+ ),
+ LocalRelation(a)
+ )
+
+
withSQLConf(SQLConf.EXCLUDE_SUBQUERY_EXP_REFS_FROM_REMOVE_REDUNDANT_ALIASES.key
-> "true") {
+ val optimized = Optimize.execute(query)
+ comparePlans(optimized, expectedWhenExcluded)
+ }
+
+
withSQLConf(SQLConf.EXCLUDE_SUBQUERY_EXP_REFS_FROM_REMOVE_REDUNDANT_ALIASES.key
-> "false") {
+ val optimized = Optimize.execute(query)
+ comparePlans(optimized, expectedWhenNotExcluded)
+ }
+ }
}
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