https://github.com/apache/spark
Revision 1576bd7b5fa0f3d24c3fa9c99f5d87668e259115 authored by Kris Mok on 17 December 2018, 05:41:20 UTC, committed by Wenchen Fan on 17 December 2018, 05:46:10 UTC
## What changes were proposed in this pull request? The optimizer rule `org.apache.spark.sql.catalyst.optimizer.ReorderJoin` performs join reordering on inner joins. This was introduced from SPARK-12032 (https://github.com/apache/spark/pull/10073) in 2015-12. After it had reordered the joins, though, it didn't check whether or not the output attribute order is still the same as before. Thus, it's possible to have a mismatch between the reordered output attributes order vs the schema that a DataFrame thinks it has. The same problem exists in the CBO version of join reordering (`CostBasedJoinReorder`) too. This can be demonstrated with the example: ```scala spark.sql("create table table_a (x int, y int) using parquet") spark.sql("create table table_b (i int, j int) using parquet") spark.sql("create table table_c (a int, b int) using parquet") val df = spark.sql(""" with df1 as (select * from table_a cross join table_b) select * from df1 join table_c on a = x and b = i """) ``` here's what the DataFrame thinks: ``` scala> df.printSchema root |-- x: integer (nullable = true) |-- y: integer (nullable = true) |-- i: integer (nullable = true) |-- j: integer (nullable = true) |-- a: integer (nullable = true) |-- b: integer (nullable = true) ``` here's what the optimized plan thinks, after join reordering: ``` scala> df.queryExecution.optimizedPlan.output.foreach(a => println(s"|-- ${a.name}: ${a.dataType.typeName}")) |-- x: integer |-- y: integer |-- a: integer |-- b: integer |-- i: integer |-- j: integer ``` If we exclude the `ReorderJoin` rule (using Spark 2.4's optimizer rule exclusion feature), it's back to normal: ``` scala> spark.conf.set("spark.sql.optimizer.excludedRules", "org.apache.spark.sql.catalyst.optimizer.ReorderJoin") scala> val df = spark.sql("with df1 as (select * from table_a cross join table_b) select * from df1 join table_c on a = x and b = i") df: org.apache.spark.sql.DataFrame = [x: int, y: int ... 4 more fields] scala> df.queryExecution.optimizedPlan.output.foreach(a => println(s"|-- ${a.name}: ${a.dataType.typeName}")) |-- x: integer |-- y: integer |-- i: integer |-- j: integer |-- a: integer |-- b: integer ``` Note that this output attribute ordering problem leads to data corruption, and can manifest itself in various symptoms: * Silently corrupting data, if the reordered columns happen to either have matching types or have sufficiently-compatible types (e.g. all fixed length primitive types are considered as "sufficiently compatible" in an `UnsafeRow`), then only the resulting data is going to be wrong but it might not trigger any alarms immediately. Or * Weird Java-level exceptions like `java.lang.NegativeArraySizeException`, or even SIGSEGVs. ## How was this patch tested? Added new unit test in `JoinReorderSuite` and new end-to-end test in `JoinSuite`. Also made `JoinReorderSuite` and `StarJoinReorderSuite` assert more strongly on maintaining output attribute order. Closes #23303 from rednaxelafx/fix-join-reorder. Authored-by: Kris Mok <rednaxelafx@gmail.com> Signed-off-by: Wenchen Fan <wenchen@databricks.com> (cherry picked from commit 56448c662398f4c5319a337e6601450270a6a27c) Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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Tip revision: 1576bd7b5fa0f3d24c3fa9c99f5d87668e259115 authored by Kris Mok on 17 December 2018, 05:41:20 UTC
[SPARK-26352][SQL] join reorder should not change the order of output attributes
[SPARK-26352][SQL] join reorder should not change the order of output attributes
Tip revision: 1576bd7
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