[jira] [Commented] (DRILL-5088) Error when reading DBRef column

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-5088?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15820028#comment-15820028 ] 

ASF GitHub Bot commented on DRILL-5088:
---------------------------------------

Github user gparai commented on a diff in the pull request:

    https://github.com/apache/drill/pull/702#discussion_r95719700
  
    --- Diff: contrib/storage-mongo/src/main/java/org/apache/drill/exec/store/mongo/MongoGroupScan.java ---
    @@ -503,7 +505,9 @@ public ScanStats getScanStats() {
           long numDocs = collection.count();
           float approxDiskCost = 0;
           if (numDocs != 0) {
    -        String json = collection.find().first().toJson();
    +        final DocumentCodec codec =
    --- End diff --
    
    Please add a comment to describe the need for the codec along with the example from the bug.


> 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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