unique index on embedded json object

[Lee Jason <jawc@xxxxxxxxxxx>]

Hi forks,

I am testing postgresql 9.4 beta2 right now.  I am wondering if it is possible to create a unique index on embedded json object?

For example,

I create a table names "products"

CREATE TABLE products (oid serial primary key, data jsonb)

Now, I try to insert json object into data column.

{"id": "12345",

"bags": [{

    "sku": "abc123",

    "price": 0,

},

{

    "sku": "abc123",

    "price": 0,

}]

}

However, I want sku of bags to be unique.  It means the json can't be inserted into products tables because sku is not unique in this case.  

I tried to create a unique index like below, but it failed.

CREATE UNIQUE INDEX product_sku_index ON products( (data->'bags'->'sku') )

Any suggestions, please?  Thank you.

Thanks,
Jason