Top-N returns the top "n" records from the input set, based on the criteria specified in the plugin configuration.

This plugin takes input records and returns a specified number of records with the highest values in a given field. If the total number of input records is smaller than the specifed number, output records will contain all records sorted by their values in the given field in a descending order.

Here is how the plugin works with a simple example. Let's say the input records have two columns ("name" and "age") and you want to track the top three records, ordered by "age", without ignoring null values. The configuration for the plugin would specify:

• Top Field as age
• Results Number as 3
• Ignore NULL Value as false

If these are the input records:

    +================+
    | name   |  age  |
    +================+
    | alice  |  NULL |
    | bob    |   1   |
    | dave   |   6   |
    +================+

then after applying the configuration, the output records will be:

    +================+
    | name   |  age  |
    +================+
    | dave   |   6   |
    | bob    |   1   |
    | alice  |  NULL |
    +================+

If the Null Field Value is set to true to ignore records with NULL values in the "age" field, the output records will be:

    +================+
    | name   |  age  |
    +================+
    | dave   |   6   |
    | bob    |   1   |
    +================+

To build this plugin:

   git clone https://github.com/hydrator/topn.git
   mvn clean package   

The build will create a .jar and .json files under the target directory. These files are used to deploy your plugins.

You can deploy your plugins using the CDAP CLI:

    > load artifact <target/topn-<version>.jar> config-file <target/topn-<version>.json>

For example, if your artifact is named 'topn-':

    > load artifact target/topn-<version>.jar config-file target/topn-<version>.json

CDAP User Group and Development Discussions:

• [email protected]

The cdap-user mailing list is primarily for users using the product to develop applications or building plugins for appplications. You can expect questions from users, release announcements, and any other discussions that we think will be helpful to the users.

CDAP IRC Channel: #cdap on irc.freenode.net

Copyright © 2017 Cask Data, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Cask is a trademark of Cask Data, Inc. All rights reserved.

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