#Delete Set Data

A Set is part of the Aerospike data model. It is similar to a table in a relational database, but more like a mathematical set. More often than not, you will store your data in a set.

During development, you will want to load data into a Set, test your application, and restore the database back to the starting point of your test. Often you will want to “drop the table” or, in Aerospike terms, delete the data from a Set.

##Problem There is no documented way to delete the data from a Set. You could create a “save point” by using asbackup to backup your database prior to the test run, then use asrestore to restore your database to the initial state. But this could be a painful and officious process, plus having side effects on other developers using the Aerospike cluster. ##Solution A utility that deletes the data in a Set written in Java so it can run anywhere java can run. It uses the Scan (Scan Namespace) API to scan through a Set and delete each record.

The source code for this solution is available on GitHub, at https://github.com/aerospike/delete-set

The utility, named delete-set, requires the Aerospike Java client, which will be downloaded from Maven Central as part of the build.

##How it works Most of the work is done using the scanAll() method on the AerospikeClient class. Consider this code snippet:

try {
	final AerospikeClient client = new AerospikeClient(host, port);

	ScanPolicy scanPolicy = new ScanPolicy();
	/*
	 * scan the entire Set using scannAll(). This will scan each node 
	 * in the cluster and return the record Digest to the call back object
	 */
	client.scanAll(scanPolicy, namespace, set, new ScanCallback() {

		public void scanCallback(Key key, Record record) throws AerospikeException {
			/*
			 * for each Digest returned, delete it using delete()
			 */
			client.delete(new WritePolicy(), key);
			count++;
			/*
			 * after 25,000 records delete, return print the count.
			 */
			if (count % 25000 == 0){
				log.info("Deleted "+ count);
			}
		}
	}, new String[] {});
	log.info("Deleted "+ count + " records from set " + set);
} catch (AerospikeException e) {
	int resultCode = e.getResultCode();
	log.info(ResultCode.getResultString(resultCode));
	log.debug("Error details: ", e);
}

The scanAll() method scans through the Set and returns the Key for each record found. It is actually the encrypted Digest that is returned, but the Java API nicely wraps it in the Key class.

The Key and Record are passed to the call back anonymous class where the delete() method is called on the record.

##Build instructions Maven is required to build delete-set. From the root directory of the project, issue the following command:

mvn clean package

Two JAR files will be produced in the directory 'target', these are:

• delete-set-<version>-jar-with-dependencies.jar - this is a runnable jar complete with all the dependencies packaged.
• delete-set-<version>.jar - this is runnable jar, but it will expect to locate it's dependencies via maven.

##Run delete-set While this utility can run on any machine, it should be run on machine that has excellent network bandwidth to the cluster.

The JAR files are runnable JARS. Here is an example command to delete the data in the Set 'demo':

java -jar delete-set-1.0.0-jar-with-dependencies.jar -h p3 -p 3000 -s demo

or

java -jar delete-set-1.0.0.jar -h p3 -p 3000 -s demo

##Options These are the options:

-h,--host <arg>  Server hostname (default: localhost)
-p,--port <arg>  Server port (default: 3000)
-s,--set  <arg>  Set to delete
-n,--namespace	 Namespace containing the Set (default: test)
-u,--usage       Print usage.