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From "Hari Sekhon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-3524) Drill proper DESCRIBE support for MongoDB
Date Tue, 21 Jul 2015 13:12:04 GMT

     [ https://issues.apache.org/jira/browse/DRILL-3524?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hari Sekhon updated DRILL-3524:
-------------------------------
    Description: 
Request to add full DESCRIBE support for MongoDB collections.

I understand this may be difficult / sub-optimal due to the flexible schema nature of Mongo
docs but if you can tabulate results when reading directly from MongoDB for which you have
read the field names, then it's also possible to extract all field names to present for the
describe command, albeit an inefficient scan to do so.

Currently describe returns a pseudo / inaccurate / unhelpful metadata:
{code}+--------------+------------+--------------+
| COLUMN_NAME  | DATA_TYPE  | IS_NULLABLE  |
+--------------+------------+--------------+
| *            | ANY        | YES          |
+--------------+------------+--------------+{code}

Perhaps you could extend DESCRIBE to scan the first few dozen docs by default to create a
merged schema as well as adding an optional argument to the describe command to allow for
scanning a user-specified number of docs from which to describe the schema, or an ALL argument
keyword to describe to scan all docs in a collection to get the complete global schema for
the collection?

In case of schema evolution it might be an interesting option to additionally read the first
and last records by ID etc.

  was:
Request to add full DESCRIBE support for MongoDB collections.

I understand this may be difficult / sub-optimal due to the flexible schema nature of Mongo
docs but if you can tabulate results when reading directly from MongoDB for which you have
read the field names, then it's also possible to extract all field names to present for the
describe command, albeit an inefficient scan to do so.

Currently describe returns a pseudo / inaccurate / unhelpful metadata:
{code}+--------------+------------+--------------+
| COLUMN_NAME  | DATA_TYPE  | IS_NULLABLE  |
+--------------+------------+--------------+
| *            | ANY        | YES          |
+--------------+------------+--------------+{code}

Perhaps you could extend DESCRIBE to scan the first few dozen docs by default to create a
merged schema as well as adding an optional argument to the describe command to allow for
scanning a user-specified number of docs from which to describe the schema, or an ALL argument
keyword to describe to scan all docs in a collection to get the complete global schema for
the collection?


> Drill proper DESCRIBE support for MongoDB
> -----------------------------------------
>
>                 Key: DRILL-3524
>                 URL: https://issues.apache.org/jira/browse/DRILL-3524
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Metadata, Storage - MongoDB
>    Affects Versions: 1.1.0
>            Reporter: Hari Sekhon
>            Assignee: Steven Phillips
>
> Request to add full DESCRIBE support for MongoDB collections.
> I understand this may be difficult / sub-optimal due to the flexible schema nature of
Mongo docs but if you can tabulate results when reading directly from MongoDB for which you
have read the field names, then it's also possible to extract all field names to present for
the describe command, albeit an inefficient scan to do so.
> Currently describe returns a pseudo / inaccurate / unhelpful metadata:
> {code}+--------------+------------+--------------+
> | COLUMN_NAME  | DATA_TYPE  | IS_NULLABLE  |
> +--------------+------------+--------------+
> | *            | ANY        | YES          |
> +--------------+------------+--------------+{code}
> Perhaps you could extend DESCRIBE to scan the first few dozen docs by default to create
a merged schema as well as adding an optional argument to the describe command to allow for
scanning a user-specified number of docs from which to describe the schema, or an ALL argument
keyword to describe to scan all docs in a collection to get the complete global schema for
the collection?
> In case of schema evolution it might be an interesting option to additionally read the
first and last records by ID etc.



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