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Posted to issues@spark.apache.org by "Apache Spark (Jira)" <ji...@apache.org> on 2021/04/20 09:37:00 UTC
[jira] [Assigned] (SPARK-35094) Spark from_json(JsonToStruct)
function return wrong value in permissive mode in case best effort
[ https://issues.apache.org/jira/browse/SPARK-35094?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Apache Spark reassigned SPARK-35094:
------------------------------------
Assignee: (was: Apache Spark)
> Spark from_json(JsonToStruct) function return wrong value in permissive mode in case best effort
> -------------------------------------------------------------------------------------------------
>
> Key: SPARK-35094
> URL: https://issues.apache.org/jira/browse/SPARK-35094
> Project: Spark
> Issue Type: Bug
> Components: Spark Core, SQL
> Affects Versions: 3.0.2, 3.1.1
> Reporter: Nick Hryhoriev
> Priority: Critical
>
> I use spark 3.1.1 and 3.0.2.
> Function `from_json` return wrong result with Permissive mode.
> In corner case:
> 1. Json message has complex nested structure
> \{sameNameField)damaged, nestedVal:{badSchemaNestedVal, sameNameField_WhichValueWillAppearInwrongPlace}}
> 2. Nested -> Nested Field: Schema is satisfy align with value in json.
> scala code to reproduce:
> {code:java}
> import org.apache.spark.sql.SparkSession
> import org.apache.spark.sql.functions.from_json
> import org.apache.spark.sql.types.IntegerType
> import org.apache.spark.sql.types.StringType
> import org.apache.spark.sql.types.StructField
> import org.apache.spark.sql.types.StructType
> object Main {
> def main(args: Array[String]): Unit = {
> implicit val spark: SparkSession = SparkSession.builder().master("local[*]").getOrCreate()
> import spark.implicits._
> val schemaForFieldWhichWillHaveWrongValue = StructField("problematicName", StringType, nullable = true)
> val nestedFieldWhichNotSatisfyJsonMessage = StructField(
> "badNestedField",
> StructType(Seq(StructField("SomethingWhichNotInJsonMessage", IntegerType, nullable = true)))
> )
> val nestedFieldWithNestedFieldWhichNotSatisfyJsonMessage =
> StructField(
> "nestedField",
> StructType(Seq(nestedFieldWhichNotSatisfyJsonMessage, schemaForFieldWhichWillHaveWrongValue))
> )
> val customSchema = StructType(Seq(
> schemaForFieldWhichWillHaveWrongValue,
> nestedFieldWithNestedFieldWhichNotSatisfyJsonMessage
> ))
> val jsonStringToTest =
> """{"problematicName":"ThisValueWillBeOverwritten","nestedField":{"badNestedField":"14","problematicName":"thisValueInTwoPlaces"}}"""
> val df = List(jsonStringToTest)
> .toDF("json")
> // issue happen only in permissive mode during best effort
> .select(from_json($"json", customSchema).as("toBeFlatten"))
> .select("toBeFlatten.*")
> df.show(truncate = false)
> assert(
> df.select("problematicName").as[String].first() == "ThisValueWillBeOverwritten",
> "wrong value in root schema, parser take value from column with same name but in another nested elvel"
> )
> }
> }
> {code}
> I was not able to debug this issue, to find the exact root cause.
> But what I find in debug, that In `org.apache.spark.sql.catalyst.util.FailureSafeParser` in line 64. code block `e.partialResult()` already have a wrong value.
> I hope this will help to fix the issue.
> I do a DIRTY HACK to fix the issue.
> I just fork this function and hardcode `None` -> `Iterator(toResultRow(None, e.record))`.
> In my case, it's better to do not have any values in the row, than theoretically have a wrong value in some column.
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