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https://issues.apache.org/jira/browse/SPARK-38091?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17486092#comment-17486092
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Erik Krogen commented on SPARK-38091:
-------------------------------------
[~Zhen-hao] for formatting you need to use the Atlassian markup:
[https://jira.atlassian.com/secure/WikiRendererHelpAction.jspa?section=all]
Basically replace ` ... ` with \{{ ... }} and replace ``` ... ``` with \{code}
... \{code}
> AvroSerializer can cause java.lang.ClassCastException at run time
> -----------------------------------------------------------------
>
> Key: SPARK-38091
> URL: https://issues.apache.org/jira/browse/SPARK-38091
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.1.0, 3.1.1, 3.1.2, 3.2.0,
> 3.2.1
> Reporter: Zhenhao Li
> Priority: Major
> Labels: Avro, serializers
>
> `AvroSerializer`'s implementation, at least in `newConverter`, was not 100%
> based on the `InternalRow` and `SpecializedGetters` interface. It assumes
> many implementation details of the interface.
> For example, in
> ```scala
> case (TimestampType, LONG) => avroType.getLogicalType match {
> // For backward compatibility, if the Avro type is Long and it is
> not logical type
> // (the `null` case), output the timestamp value as with
> millisecond precision.
> case null | _: TimestampMillis => (getter, ordinal) =>
>
> DateTimeUtils.microsToMillis(timestampRebaseFunc(getter.getLong(ordinal)))
> case _: TimestampMicros => (getter, ordinal) =>
> timestampRebaseFunc(getter.getLong(ordinal))
> case other => throw new IncompatibleSchemaException(errorPrefix +
> s"SQL type ${TimestampType.sql} cannot be converted to Avro
> logical type $other")
> }
> ```
> it assumes the `InternalRow` instance encodes `TimestampType` as
> `java.lang.Long`. That's true for `Unsaferow` but not for
> `GenericInternalRow`.
> Hence the above code will end up with runtime exceptions when used on an
> instance of `GenericInternalRow`, which is the case for Python UDF.
> I didn't get time to dig deeper than that. I got the impression that Spark's
> optimizer(s) will turn a row into a `UnsafeRow` and Python UDF doesn't
> involve the optimizer(s) and hence each row is a `GenericInternalRow`.
> It would be great if someone can correct me or offer a better explanation.
>
> To reproduce the issue,
> `git checkout master` and `git cherry-pick --no-commit`
> [this-commit|https://github.com/Zhen-hao/spark/commit/1ffe8e8f35273b2f3529f6c2d004822f480e4c88]
> and run the test `org.apache.spark.sql.avro.AvroSerdeSuite`.
>
> You will see runtime exceptions like the following one
> ```
> - Serialize DecimalType to Avro BYTES with logical type decimal *** FAILED ***
> java.lang.ClassCastException: class java.math.BigDecimal cannot be cast to
> class org.apache.spark.sql.types.Decimal (java.math.BigDecimal is in module
> java.base of loader 'bootstrap'; org.apache.spark.sql.types.Decimal is in
> unnamed module of loader 'app')
> at
> org.apache.spark.sql.catalyst.expressions.BaseGenericInternalRow.getDecimal(rows.scala:45)
> at
> org.apache.spark.sql.catalyst.expressions.BaseGenericInternalRow.getDecimal$(rows.scala:45)
> at
> org.apache.spark.sql.catalyst.expressions.GenericInternalRow.getDecimal(rows.scala:195)
> at
> org.apache.spark.sql.avro.AvroSerializer.$anonfun$newConverter$10(AvroSerializer.scala:136)
> at
> org.apache.spark.sql.avro.AvroSerializer.$anonfun$newConverter$10$adapted(AvroSerializer.scala:135)
> at
> org.apache.spark.sql.avro.AvroSerializer.$anonfun$newStructConverter$2(AvroSerializer.scala:283)
> at
> org.apache.spark.sql.avro.AvroSerializer.serialize(AvroSerializer.scala:60)
> at
> org.apache.spark.sql.avro.AvroSerdeSuite.$anonfun$new$5(AvroSerdeSuite.scala:82)
> at
> org.apache.spark.sql.avro.AvroSerdeSuite.$anonfun$new$5$adapted(AvroSerdeSuite.scala:67)
> at
> org.apache.spark.sql.avro.AvroSerdeSuite.$anonfun$withFieldMatchType$2(AvroSerdeSuite.scala:217)
> ```
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