MapR-DB JSON Tables

JSON documents are stored in MapR-DB JSON tables. MapR-DB supports schema flexibility in the documents and provides the tools to efficiently access them. It optimizes the storage of the JSON documents, providing high performance.

When a JSON document is added to a JSON table, it is put in a table row. The table row is part of one column family (although you can create more, as described in Column Families in JSON Tables). The value in the row is a single JSON document that is stored in a binary format. The binary format allows MapR-DB to make a number of optimizations to the document’s layout to make data access fast and efficient. MapR-DB also maintains the data types associated with fields in a JSON document.

The JSON documents in a table need not have identical structures. It is possible to include in a table any number of JSON documents that have no common fields or share only a subset of fields.

For example, an online retailer might have the following three documents in a single JSON table. Only a subset of fields is common to all three documents. These are key differences:

Each document has a different nested document in a field named specifications.
Only two of the documents have arrays in the field features.
The retailers field has different types in the first and third documents.

{
    "_id" : "ID1",
    "product_ID" : "4GGC859",
    "name" : "Thresher 1000",
    "brand" : "Careen",
    "category" : "Bicycle",
    "type" : "Road bicycle",
    "price" : 2949.99,

    "specifications" : {
        "size" : "55cm",
        "wheel_size" : "700c",
        "frameset" : {
            "frame" : "Carbon Enduro",
            "fork" : "Gabel 2"
        },
        "groupset" : {
            "chainset" : "Kette 230",
            "brake" : "Bremse FullStop"
	  },
        "wheelset" : {
	        "wheels" : "Rad Schnell 10",
	        "tyres" : "Reifen Pro"
        }
    },

    "retailers": {
        "name" : "Eden Bicycles",
        "location" : {
            "city" : "Castro Valley",
            "state" : "CA"
        }
    }
}

{
    "_id" : "ID2",
    "product_ID" : "2DT3201",
    "name" : " Allegro SPD-SL 6800",
    "brand" : "Careen",
    "category" : "Pedals",
    "type" : "Components",
    "price" : 112.99,

    "features" : [
        "Low-profile design",
        "Floating SH11 cleats included"
    ],

    "specifications" : {
        "weight_per_pair" : "260g",
        "color" : "black"
    }
}

{
    "_id" : "ID3",
    "product_ID" : "3ML6758",
    "name" : "Trikot 24-LK",
    "brand" : "Careen",
    "category" : "Jersey",
    "type" : "Clothing",
    "price" : 76.99,

    "features" : [
        "Wicks away moisture.",
        "SPF-30",
        "Reflects light at night."
    ],

    "specifications" : {
        "sizes" : ["S","M","L","XL","XXL"],
        "colors" : [
            "white",
            "navy",
            "green"
        ]
    },

    "retailers" : [
        {
            "name" : "Bespoke Cycles",
            "city": "San Francisco",
            "state" : "CA"
        },
        {
            "name" : "Trek Bicycle",
            "city" : "New York",
            "state" : "NY"
        }
    ]       
}

Table Paths

Tables are stored in the MapR file system. When providing the path to a table in MapR tools and APIs, use these conventions:

For a path on the local cluster, start the path at the volume mount point. For example, for a table named test under a volume with a mount point at /volume1, specify the following path: /volume1/test
For a path on a remote cluster, you must also specify the cluster name in the path. For example, for a table named customer in volume1 in the sanfrancisco cluster, specify the following path: /mapr/sanfrancisco/volume1/customer

Tools for Creating and Administering JSON Tables

These are the tools available for creating and administering JSON tables in MapR-DB:

MapR-DB Shell: This shell is a light-weight tool for manipulating JSON tables and documents. Learn more about it at MapR-DB Shell (JSON Tables).
MapR-DB JSON Client API: This API allows you to manage MapR-DB JSON tables. The API includes methods to create, alter, and drop tables and column families. Learn more about these APIs at Managing JSON Tables.
MapR-DB JSON REST API: The REST API allows you to create and drop MapR-DB JSON tables using HTTP calls. Learn more about it at Using the MapR-DB JSON REST API.
MapR-DB JSON utilities: MapR-DB JSON supports several utilities for loading tables. Learn more about these utilities at Loading Documents into JSON Tables.
maprcli commands: The maprcli table commands fully support JSON tables. See table.

NOTE: For a list of tools available to query and manage documents in MapR-DB JSON tables, see Tools for Working with JSON Documents.