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From Tyler Coffin <tcof...@gmail.com>
Subject REST Interface: Required ordering of JSON name/value pairs when performing Insert/Update
Date Tue, 20 Apr 2010 19:37:12 GMT
Good day,

I am using the Stargate REST interface to HBase for inserting data.
When using JSON to transmit the query content, I have found that
specific ordering of key/value pairs within the JSON string is
required in order for the query to succeed (otherwise a response of
'HTTP/1.1 500 Row key is invalid' error is thrown if "key" and "Cell"
are reversed).

Example:
This string receives the above error:
{"Row":[{"Cell":[{"column":"bWVzc2FnZTptc2c=","$":"Zm9vYmFy"}],"key":"MTIzNAo="}]}
This is the valid equivalent string:
{"Row":[{"key":"MTIzNAo=","Cell":[{"column":"bWVzc2FnZTptc2c=","$":"Zm9vYmFy"}]}]}
As you can see the only difference between these two instances is that
the "key" and "Cell" name/value pairs have their order reversed.

In the equivalent XML notation, the ordering is specifically required
per the schema. However with JSON Objects (i.e. name/value pairs)
order is not required (JSON Arrays are ordered, but not Objects). Some
JSON libraries will preserve ordering of Objects but not all (which is
how I discovered this problem in the first place because I was using
the Perl JSON library which does not guarantee order).

I'm unsure if this is a bug in the REST implementation or an
inconvenient ambiguity in the JSON specification. Regardless I thought
I'd share this discovery with the community for feedback (or at the
very least to document this for users' future reference).

For reference this is the table schema for the above query:
{NAME => 'reftrack', FAMILIES => [{NAME => 'message', COMPRESSION =>
'NONE', VERSIONS => '1', TTL => '2147483647', BLOCKSIZE => '65536',
IN_MEMORY => 'false', BLOCKCACHE => 'true'}]}

Cheers,

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