[
https://issues.apache.org/jira/browse/SPARK-45311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17789867#comment-17789867
]
Giambattista Bloisi commented on SPARK-45311:
---------------------------------------------
The issue arise while Encoders.bean is inferring the schema for JeuDeDonnees
class. This class has a field of type Ressources.class which extends a
LinkedHashMap<RessourceJeuDeDonneesId, Ressource>.
A simple work-around to let the tests pass is to modify the JeuDeDonnees and
declare ressources as a Map:
{code:java}
private Map<RessourceJeuDeDonneesId, Ressource> ressources;
//...
public Map<RessourceJeuDeDonneesId, Ressource> getRessources() {
//...{code}
and, when required, iterate the values explicitly:
{code:java}
jeuDeDonnees.getRessources().values().forEach {code}
The exception is thrown because the code assumes (wrongly in that case) that if
a class (such as Ressources.class) is a Map, then it has generic type
information attached to it, here instead the information is available in the
base/super class.
There is a wider problem behind this. There are cases where mapping to a Spark
schema would be ambigous, for example:
* Ressources could have also getters and setters, should it be mapped as a map
or a struct?
* A class could implement both List and Map interfaces. should it be mapped as
an array or a map?
IMO the workaround is also a good idiomatic way to structure beans to be used
with Spark, as it makes the mapping explicit and removes the possibility of
ambiguities.
> Encoder fails on many "NoSuchElementException: None.get" since 3.4.x, search
> for an encoder for a generic type, and since 3.5.x isn't "an expression
> encoder"
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-45311
> URL: https://issues.apache.org/jira/browse/SPARK-45311
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 3.4.0, 3.4.1, 3.5.0
> Environment: Debian 12
> Java 17
> Underlying Spring-Boot 2.7.14
> Reporter: Marc Le Bihan
> Priority: Major
> Attachments: JavaTypeInference_116.png, sparkIssue_02.png
>
>
> If you find it convenient, you might clone the
> [https://gitlab.com/territoirevif/minimal-tests-spark-issue] project (that
> does many operations around cities, local authorities and accounting with
> open data) where I've extracted from my work what's necessary to make a set
> of 35 tests that run correctly with Spark 3.3.x, and show the troubles
> encountered with 3.4.x and 3.5.x.
>
> It is working well with Spark 3.2.x, 3.3.x. But as soon as I selec{*}t Spark
> 3.4.x{*}, where the encoder seems to have deeply changed, the encoder fails
> with two problems:
>
> *1)* It throws *java.util.NoSuchElementException: None.get* messages
> everywhere.
> Asking over the Internet, I wasn't alone facing this problem. Reading it,
> you'll see that I've attempted a debug but my Scala skills are low.
> [https://stackoverflow.com/questions/76036349/encoders-bean-doesnt-work-anymore-on-a-java-pojo-with-spark-3-4-0]
> {color:#172b4d}by the way, if possible, the encoder and decoder functions
> should forward a parameter as soon as the name of the field being handled is
> known, and then all the long of their process, so that when the encoder is at
> any point where it has to throw an exception, it knows the field it is
> handling in its specific call and can send a message like:{color}
> {color:#00875a}_java.util.NoSuchElementException: None.get when encoding [the
> method or field it was targeting]_{color}
>
> *2)* *Not found an encoder of the type RS to Spark SQL internal
> representation.* Consider to change the input type to one of supported at
> (...)
> Or : Not found an encoder of the type *OMI_ID* to Spark SQL internal
> representation (...)
>
> where *RS* and *OMI_ID* are generic types.
> This is strange.
> [https://stackoverflow.com/questions/76045255/encoders-bean-attempts-to-check-the-validity-of-a-return-type-considering-its-ge]
>
> *3)* When I switch to the *Spark 3.5.0* version, the same problems remain,
> but another add itself to the list:
> "{*}Only expression encoders are supported for now{*}" on what was accepted
> and working before.
>
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
