[SPARK-39061][SQL] Set nullable correctly for Inline output attributes
#36883
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HyukjinKwon
reviewed
Jun 16, 2022
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
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Jun 16, 2022
|
Merged to master, branch-3.3 and branch-3.2. |
HyukjinKwon
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### What changes were proposed in this pull request?
Change `Inline#elementSchema` to make each struct field nullable when the containing array has a null element.
### Why are the changes needed?
This query returns incorrect results (the last row should be `NULL NULL`):
```
spark-sql> select inline(array(named_struct('a', 1, 'b', 2), null));
1 2
-1 -1
Time taken: 4.053 seconds, Fetched 2 row(s)
spark-sql>
```
And this query gets a NullPointerException:
```
spark-sql> select inline(array(named_struct('a', '1', 'b', '2'), null));
22/04/28 16:51:54 ERROR Executor: Exception in task 0.0 in stage 2.0 (TID 2)
java.lang.NullPointerException: null
at org.apache.spark.sql.catalyst.expressions.codegen.UnsafeWriter.write(UnsafeWriter.java:110) ~[spark-catalyst_2.12-3.4.0-SNAPSHOT.jar:3.4.0-SNAPSHOT]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.generate_doConsume_0$(Unknown Source) ~[?:?]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source) ~[?:?]
at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(Buffere
```
When an array of structs is created by `CreateArray`, and no struct field contains a literal null value, the schema for the struct will have non-nullable fields, even if the array itself has a null entry (as in the example above). As a result, the output attributes for the generator will be non-nullable.
When the output attributes for `Inline` are non-nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` generates incorrect code for null structs.
In more detail, the issue is this: `GenerateExec#codeGenCollection` generates code that will check if the struct instance (i.e., array element) is null and, if so, set a boolean for each struct field to indicate that the field contains a null. However, unless the generator's output attributes are nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` will not generate any code to check those booleans. Instead it will generate code to write out whatever is in the variables that normally hold the struct values (which will be garbage if the array element is null).
Arrays of structs from file sources do not have this issue. In that case, each `StructField` will have nullable=true due to [this](https://github.com/apache/spark/blob/fe85d7912f86c3e337aa93b23bfa7e7e01c0a32e/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSource.scala#L417).
(Note: the eval path for `Inline` has a different bug with null array elements that occurs even when `nullable` is set correctly in the schema, but I will address that in a separate PR).
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
New unit test.
Closes #36883 from bersprockets/inline_struct_nullability_issue.
Authored-by: Bruce Robbins <[email protected]>
Signed-off-by: Hyukjin Kwon <[email protected]>
(cherry picked from commit fc385da)
Signed-off-by: Hyukjin Kwon <[email protected]>
HyukjinKwon
pushed a commit
that referenced
this pull request
Jun 16, 2022
Change `Inline#elementSchema` to make each struct field nullable when the containing array has a null element.
This query returns incorrect results (the last row should be `NULL NULL`):
```
spark-sql> select inline(array(named_struct('a', 1, 'b', 2), null));
1 2
-1 -1
Time taken: 4.053 seconds, Fetched 2 row(s)
spark-sql>
```
And this query gets a NullPointerException:
```
spark-sql> select inline(array(named_struct('a', '1', 'b', '2'), null));
22/04/28 16:51:54 ERROR Executor: Exception in task 0.0 in stage 2.0 (TID 2)
java.lang.NullPointerException: null
at org.apache.spark.sql.catalyst.expressions.codegen.UnsafeWriter.write(UnsafeWriter.java:110) ~[spark-catalyst_2.12-3.4.0-SNAPSHOT.jar:3.4.0-SNAPSHOT]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.generate_doConsume_0$(Unknown Source) ~[?:?]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source) ~[?:?]
at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(Buffere
```
When an array of structs is created by `CreateArray`, and no struct field contains a literal null value, the schema for the struct will have non-nullable fields, even if the array itself has a null entry (as in the example above). As a result, the output attributes for the generator will be non-nullable.
When the output attributes for `Inline` are non-nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` generates incorrect code for null structs.
In more detail, the issue is this: `GenerateExec#codeGenCollection` generates code that will check if the struct instance (i.e., array element) is null and, if so, set a boolean for each struct field to indicate that the field contains a null. However, unless the generator's output attributes are nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` will not generate any code to check those booleans. Instead it will generate code to write out whatever is in the variables that normally hold the struct values (which will be garbage if the array element is null).
Arrays of structs from file sources do not have this issue. In that case, each `StructField` will have nullable=true due to [this](https://github.com/apache/spark/blob/fe85d7912f86c3e337aa93b23bfa7e7e01c0a32e/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSource.scala#L417).
(Note: the eval path for `Inline` has a different bug with null array elements that occurs even when `nullable` is set correctly in the schema, but I will address that in a separate PR).
No.
New unit test.
Closes #36883 from bersprockets/inline_struct_nullability_issue.
Authored-by: Bruce Robbins <[email protected]>
Signed-off-by: Hyukjin Kwon <[email protected]>
(cherry picked from commit fc385da)
Signed-off-by: Hyukjin Kwon <[email protected]>
HyukjinKwon
reviewed
Jun 20, 2022
| @@ -389,6 +389,31 @@ class GeneratorFunctionSuite extends QueryTest with SharedSparkSession { | |||
| Row(0, 1) :: Row(3, 4) :: Row(6, 7) :: Row(null, null) :: Row(null, null) :: Nil) | |||
| } | |||
| } | |||
|
|
|||
| test("SPARK-39061: inline should handle null struct") { | |||
There was a problem hiding this comment.
Seems like this fails in Scala 2.13 for some reasons. I filed a JIRA at https://issues.apache.org/jira/browse/SPARK-39524
There was a problem hiding this comment.
@HyukjinKwon I will take a look.
There was a problem hiding this comment.
I resolved that Jira (and a few others) as a dup of SPARK-39520 ("ExpressionSetSuite test failure with Scala 2.13") since those failures are fixed by SPARK-39520's proposed fix.
sunchao
pushed a commit
to sunchao/spark
that referenced
this pull request
Jun 2, 2023
Change `Inline#elementSchema` to make each struct field nullable when the containing array has a null element.
This query returns incorrect results (the last row should be `NULL NULL`):
```
spark-sql> select inline(array(named_struct('a', 1, 'b', 2), null));
1 2
-1 -1
Time taken: 4.053 seconds, Fetched 2 row(s)
spark-sql>
```
And this query gets a NullPointerException:
```
spark-sql> select inline(array(named_struct('a', '1', 'b', '2'), null));
22/04/28 16:51:54 ERROR Executor: Exception in task 0.0 in stage 2.0 (TID 2)
java.lang.NullPointerException: null
at org.apache.spark.sql.catalyst.expressions.codegen.UnsafeWriter.write(UnsafeWriter.java:110) ~[spark-catalyst_2.12-3.4.0-SNAPSHOT.jar:3.4.0-SNAPSHOT]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.generate_doConsume_0$(Unknown Source) ~[?:?]
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIteratorForCodegenStage1.processNext(Unknown Source) ~[?:?]
at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(Buffere
```
When an array of structs is created by `CreateArray`, and no struct field contains a literal null value, the schema for the struct will have non-nullable fields, even if the array itself has a null entry (as in the example above). As a result, the output attributes for the generator will be non-nullable.
When the output attributes for `Inline` are non-nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` generates incorrect code for null structs.
In more detail, the issue is this: `GenerateExec#codeGenCollection` generates code that will check if the struct instance (i.e., array element) is null and, if so, set a boolean for each struct field to indicate that the field contains a null. However, unless the generator's output attributes are nullable, `GenerateUnsafeProjection#writeExpressionsToBuffer` will not generate any code to check those booleans. Instead it will generate code to write out whatever is in the variables that normally hold the struct values (which will be garbage if the array element is null).
Arrays of structs from file sources do not have this issue. In that case, each `StructField` will have nullable=true due to [this](https://github.com/apache/spark/blob/fe85d7912f86c3e337aa93b23bfa7e7e01c0a32e/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSource.scala#L417).
(Note: the eval path for `Inline` has a different bug with null array elements that occurs even when `nullable` is set correctly in the schema, but I will address that in a separate PR).
No.
New unit test.
Closes apache#36883 from bersprockets/inline_struct_nullability_issue.
Authored-by: Bruce Robbins <[email protected]>
Signed-off-by: Hyukjin Kwon <[email protected]>
(cherry picked from commit fc385da)
Signed-off-by: Hyukjin Kwon <[email protected]>
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What changes were proposed in this pull request?
Change
Inline#elementSchemato make each struct field nullable when the containing array has a null element.Why are the changes needed?
This query returns incorrect results (the last row should be
NULL NULL):And this query gets a NullPointerException:
When an array of structs is created by
CreateArray, and no struct field contains a literal null value, the schema for the struct will have non-nullable fields, even if the array itself has a null entry (as in the example above). As a result, the output attributes for the generator will be non-nullable.When the output attributes for
Inlineare non-nullable,GenerateUnsafeProjection#writeExpressionsToBuffergenerates incorrect code for null structs.In more detail, the issue is this:
GenerateExec#codeGenCollectiongenerates code that will check if the struct instance (i.e., array element) is null and, if so, set a boolean for each struct field to indicate that the field contains a null. However, unless the generator's output attributes are nullable,GenerateUnsafeProjection#writeExpressionsToBufferwill not generate any code to check those booleans. Instead it will generate code to write out whatever is in the variables that normally hold the struct values (which will be garbage if the array element is null).Arrays of structs from file sources do not have this issue. In that case, each
StructFieldwill have nullable=true due to this.(Note: the eval path for
Inlinehas a different bug with null array elements that occurs even whennullableis set correctly in the schema, but I will address that in a separate PR).Does this PR introduce any user-facing change?
No.
How was this patch tested?
New unit test.