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Background UDF Example

In this example a user sees that after a code push new records are getting accidentally set to never expire (TTL -1 from the client). The user wants to identify these records and reset their TTL to 7 days.

We'll use a predicate filter to identify the records, and a background UDF to modify the TTL of matched records.

Background UDF​

A background UDF is a record UDF that modifies a record and returns no result. As such, it can be attached to a scan or query to operate on record after record.

ttl.lua

function set_ttl(rec, to_ttl)
  record.set_ttl(rec, to_ttl)
  aerospike:update(rec)
end

Register the Module​

In AQL:

aql> register module './ttl.lua'
OK, 1 module added.

Predicate Filter​

We'll use a predicate filter to find records with a void time of 0.

In the Java client:

Statement stmt = new Statement();
stmt.setNamespace(params.namespace);
stmt.setSetName(params.set);
stmt.setPredExp(
  PredExp.recVoidTime(),
  PredExp.integerValue(0),
  PredExp.integerEqual()
  );

ExecuteTask task = client.execute(params.writePolicy, stmt, "ttl", "set_ttl", Value.IntegerValue(604800));
task.waitTillComplete();

Without Using the Predicate Filter​

If the language client doesn't have support for predicate filtering the logic to identify the record can be moved into the UDF. This is less efficient, but functionally the same.

ttl.lua

function modify_zero_ttl(rec, to_ttl)
  local rec_ttl = record.ttl(rec)
  if rec_ttl == 0 then
    record.set_ttl(rec, to_ttl)
    aerospike:update(rec)
  end
end

Now from AQL:

aql> register module './ttl.lua'
OK, 1 module added.

aql> execute ttl.modify_zero_ttl(604800) on test.foo