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https://issues.apache.org/jira/browse/DRILL-5088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15820475#comment-15820475
]
ASF GitHub Bot commented on DRILL-5088:
---------------------------------------
Github user chunhui-shi commented on the issue:
https://github.com/apache/drill/pull/702
MongoGroupScan tries to read first record to guess record width. So this
toJson is called for only first record.
Notice that MongoClient.getDefaultCodecRegistry() contains
DBRefCodecProvider:
Shown in MongoClient.java(In MongoClient.java):
private static final CodecRegistry DEFAULT_CODEC_REGISTRY =
fromProviders(asList(new ValueCodecProvider(),
new DBRefCodecProvider(),
new DocumentCodecProvider(new
DocumentToDBRefTransformer()),
new DBObjectCodecProvider(),
new BsonValueCodecProvider(),
new GeoJsonCodecProvider()));
but a default DocumentCodec constructor does not. And it was this
constructor get called if we don't set a codec for toJson function to use. The
list of CodecProviders is shown in DocumentCodec.java in MongoDb's code:
public class DocumentCodec implements CollectibleCodec<Document> {
private static final String ID_FIELD_NAME = "_id";
private static final CodecRegistry DEFAULT_REGISTRY =
fromProviders(asList(new ValueCodecProvider(),
new BsonValueCodecProvider(),
new DocumentCodecProvider()));
> Error when reading DBRef column
> -------------------------------
>
> Key: DRILL-5088
> URL: https://issues.apache.org/jira/browse/DRILL-5088
> Project: Apache Drill
> Issue Type: Bug
> Components: Execution - Data Types
> Environment: drill 1.9.0
> mongo 3.2
> Reporter: Guillaume Champion
> Assignee: Chunhui Shi
>
> In a mongo database with DBRef, when a DBRef is inserted in the first line of
> a mongo's collection drill query failed :
> {code}
> 0: jdbc:drill:zk=local> select * from mongo.mydb.contact2;
> Error: SYSTEM ERROR: CodecConfigurationException: Can't find a codec for
> class com.mongodb.DBRef.
> {code}
> Simple example to reproduce:
> In mongo instance
> {code}
> db.contact2.drop();
> db.contact2.insert({ "_id" : ObjectId("582081d96b69060001fd8938"), "account"
> : DBRef("contact", ObjectId("999cbf116b69060001fd8611")) });
> {code}
> In drill :
> {code}
> 0: jdbc:drill:zk=local> select * from mongo.mydb.contact2;
> Error: SYSTEM ERROR: CodecConfigurationException: Can't find a codec for
> class com.mongodb.DBRef.
> [Error Id: 2944d766-e483-4453-a706-3d481397b186 on Analytics-Biznet:31010]
> (state=,code=0)
> {code}
> If the first line doesn't contain de DBRef, drill will querying correctly :
> In a mongo instance :
> {code}
> db.contact2.drop();
> db.contact2.insert({ "_id" : ObjectId("582081d96b69060001fd8939") });
> db.contact2.insert({ "_id" : ObjectId("582081d96b69060001fd8938"), "account"
> : DBRef("contact", ObjectId("999cbf116b69060001fd8611")) });
> {code}
> In drill :
> {code}
> 0: jdbc:drill:zk=local> select * from mongo.mydb.contact2;
> +--------------------------------------+---------------------------------------------------------------+
> | _id | account
> |
> +--------------------------------------+---------------------------------------------------------------+
> | {"$oid":"582081d96b69060001fd8939"} | {"$id":{}}
> |
> | {"$oid":"582081d96b69060001fd8938"} |
> {"$ref":"contact","$id":{"$oid":"999cbf116b69060001fd8611"}} |
> +--------------------------------------+---------------------------------------------------------------+
> 2 rows selected (0,563 seconds)
> {code}
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