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Querying Metadata

  • Capella Columnar
  • reference
    +
    You can review information about your Capella Columnar entities by querying the collections in the System.Metadata scope.

    For metadata introspection, the System.Metadata scope contains the following collections:

    • Database

    • Dataverse, for scope metadata

    • Dataset, for collection metadata

    • Function

    • Index

    • Link

    • Synonym

    Each collection contains the queryable metadata for that entity type.

    Each of these collection identifiers is a reserved word. As a result, you must escape these names with backticks (``), as shown in the examples that follow.

    For more information about metadata storage, see Metadata Storage.

    Examples

    This example returns the metadata for a single link object so that you can identify the field names for further querying:

      SELECT * FROM System.Metadata.`Link` LIMIT 1;

    Returns:

      {
    "Link": {
      "Name": "capellaLink",
      "Type": "COUCHBASE",
      "IsActive": true
    }
  }

    To get additional information about a link, you can use a DESCRIBE LINK statement.

    The next example returns the metadata for a specific collection. In its results, you can then verify the values for its Amazon S3 bucket—or ON clause—and path by inspecting the container and definition properties respectively.

      SELECT * from System.Metadata.`Dataset`
    WHERE DatasetName = "rockSongs";

    Returns:

    [
  {
    "Dataset": {
    "DatabaseName": "music",
    "DataverseName": "myPlaylist",
    "DatasetName": "rockSongs",
    "DatatypeDataverseName": "Metadata",
    "DatatypeName": "AnyObject",
    "DatasetType": "EXTERNAL",
    "GroupName": "music.myPlaylist.rockSongs",
    "CompactionPolicy": "",
    "CompactionPolicyProperties": [],
    "ExternalDetails": {
      "DatasourceAdapter": "LINK",
      "Properties": [
        {
          "Name": "container",
          "Value": "music"
        },
        {
          "Name": "name",
          "Value": "musicLink"
        },
        {
          "Name": "format",
          "Value": "json"
        },
        {
          "Name": "database",
          "Value": "music"
        },
        {
          "Name": "definition",
          "Value": "music/myPlaylist/rockSongs"
        },
        {
          "Name": "dataverse",
          "Value": "myPlaylist"
        }
      ],
      "LastRefreshTime": "2024-02-02T15:23:08.508",
      "TransactionState": 0
    },
    "Hints": [],
    "Timestamp": "Fri Feb 02 15:23:08 GMT 2024",
    "DatasetId": 117,
    "PendingOp": 0,
    "DatatypeDatabaseName": "System",
    "DatasetFormat": {
      "Format": "ROW"
      }
    }
  }
]

    The next example returns the qualified names of all collections that are not themselves in the System.Metadata scope.

      SELECT VALUE d.DatabaseName || '.' || d.DataverseName || '.' || d.DatasetName
  FROM System.Metadata.`Dataset` d
  WHERE d.DataverseName <> "Metadata";

    Returns:

    [
  "sampleAnalytics.Commerce.customers",
  "sampleAnalytics.Commerce.orders",
  "music.myPlaylist.rockSongs",
  "music.myPlaylist.countrySongs"
]

    See Also