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From "Sushanth Sowmyan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-6166) JsonSerDe is too strict about table schema
Date Sat, 11 Jan 2014 00:58:52 GMT

    [ https://issues.apache.org/jira/browse/HIVE-6166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13868552#comment-13868552
] 

Sushanth Sowmyan commented on HIVE-6166:
----------------------------------------

Agreed, updating.

> JsonSerDe is too strict about table schema
> ------------------------------------------
>
>                 Key: HIVE-6166
>                 URL: https://issues.apache.org/jira/browse/HIVE-6166
>             Project: Hive
>          Issue Type: Bug
>          Components: HCatalog, Serializers/Deserializers
>    Affects Versions: 0.12.0
>            Reporter: Sushanth Sowmyan
>            Assignee: Sushanth Sowmyan
>         Attachments: HIVE-6166.2.patch, HIVE-6166.patch
>
>
> JsonSerDe is too strict when it comes to schema, erroring out if it finds a subfield
with a key name that does not map to an appropriate type/schema of a table, or an inner-struct
schema.
> Thus, if a schema specifies "s:struct<a:int,b:string>,k:int" and we pass it data
that looks like the following:
> {noformat}
> { "x" : "abc" , "s" : { "a" : 2 , "b" : "blah", "c": "woo" } }
> {noformat}
> This should still pass, and the record should be read as if it were 
> {noformat}
> { "s" : { "a" : 2 , "b" : "blah"}, k :  null }
> {noformat}
> This will allow the JsonSerDe to be used with a wider set of data where the data does
not map too finely to the declared table schema.
> Note, we are still strict about a couple of things:
> a) If there is a declared schema column, then the type cannot vary, that is still considered
an error. i.e., if the hive table schema says k1 is a boolean, it cannot magically change
into an int or a struct, say, for eg.
> b) The JsonSerDe still attempts to map hive internal column names - i.e. if the data
contains a column named "_col2", then, if "_col2" is not declared directly in the schema,
it will map to column position 2 in that schema/subschema, rather than ignoring the field.
This is so that tables created with CTAS will still work. 



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