Vincent Doba created SPARK-36874:
------------------------------------
Summary: Ambiguous Self-Join detected only on right dataframe
Key: SPARK-36874
URL: https://issues.apache.org/jira/browse/SPARK-36874
Project: Spark
Issue Type: Bug
Components: SQL
Affects Versions: 3.1.2
Reporter: Vincent Doba
When joining two dataframes, if they share the same lineage and one dataframe
is a transformation of the other, Ambiguous Self Join detection only works when
transformed dataframe is the right dataframe.
For instance {{df1}} and {{df2}} where {{df2}} is a filtered {{df1}}, Ambiguous
Self Join detection only works when {{df2}} is the right dataframe:
- {{df1.join(df2, ...)}} correctly fails with Ambiguous Self Join error
- {{df2.join(df1, ...)}} returns a valid dataframe
h1. Minimum Reproducible example
h2. Code
{code:scala}
import sparkSession.implicit._
val df1 = Seq((1, 2, "A1"),(3,4, "A2")).toDF("key1", "key2", "value")
val df2 = df1.filter($"value" === "A2")
df2.join(df1, df1("key1") === df2("key2")).show()
{code}
h2. Expected Result
Throw the following exception:
{code}
Exception in thread "main" org.apache.spark.sql.AnalysisException: Column
key2#11 are ambiguous. It's probably because you joined several Datasets
together, and some of these Datasets are the same. This column points to one of
the Datasets but Spark is unable to figure out which one. Please alias the
Datasets with different names via `Dataset.as` before joining them, and specify
the column using qualified name, e.g. `df.as("a").join(df.as("b"), $"a.id" >
$"b.id")`. You can also set spark.sql.analyzer.failAmbiguousSelfJoin to false
to disable this check.
at
org.apache.spark.sql.execution.analysis.DetectAmbiguousSelfJoin$.apply(DetectAmbiguousSelfJoin.scala:157)
at
org.apache.spark.sql.execution.analysis.DetectAmbiguousSelfJoin$.apply(DetectAmbiguousSelfJoin.scala:43)
at
org.apache.spark.sql.catalyst.rules.RuleExecutor.$anonfun$execute$2(RuleExecutor.scala:216)
at
scala.collection.LinearSeqOptimized.foldLeft(LinearSeqOptimized.scala:126)
at
scala.collection.LinearSeqOptimized.foldLeft$(LinearSeqOptimized.scala:122)
at scala.collection.immutable.List.foldLeft(List.scala:91)
{code}
h2. Actual result
Empty dataframe:
{code:java}
+----+----+-----+----+----+-----+
|key1|key2|value|key1|key2|value|
+----+----+-----+----+----+-----+
+----+----+-----+----+----+-----+
{code}
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
