Scheduler

OrientDB has a Scheduler of events you can use to fire your events on regular basis. To manage events you can use both SQL and Java API. The scheduler gets the popular CRON expression syntax. The scheduled event, when fired, executes a Database

Resources

• CRON expressions on Wikipedia
• CRON expression maker is an online resource to create CRON expressions

Schedule an event

Via SQL

In order to schedule a new event via SQL, all you need is to create a new record in the OSchedule class. Example on scheduling the event "myEvent" that calls the function "myFunction" every second:

INSERT INTO oschedule
  SET name = 'myEvent',
      function = (SELECT FROM ofunction WHERE name = 'myFunction'),
      rule = \"0/1 * * * * ?\"

Via Java API

db.getMetadata().getScheduler().scheduleEvent(
  new OScheduledEventBuilder().setName("myEvent").setRule("0/1 * * * * ?")
  .setFunction(func).build());

Update an event

Via SQL

To update the scheduling of an event, update the record with the new rule. Example:

UPDATE oschedule SET rule = "0/2 * * * * ?" WHERE name = 'myEvent'

Via Java API

To update an event, remove it and reschedule it.

db.getMetadata().getScheduler().removeEvent("myEvent");
db.getMetadata().getScheduler().scheduleEvent(
  new OScheduledEventBuilder().setName("myEvent").setRule("0/2 * * * * ?")
  .setFunction(func).build());

Remove an event

Via SQL

To cancel a scheduled event, just delete the record. Example:

DELETE oschedule WHERE name = 'myEvent'

Via Java API

db.getMetadata().getScheduler().removeEvent("myEvent");

Tutorial

In this tutorial we want to purge all the records older than 1 year.

1) Create a Function

First, create a SQL function that delete the records. To have the date of 1y ago you can use the expression sysdate() - 31536000000, where 31536000000 represents the number of milliseconds in a year. You can this via SQL or Java API.

Via SQL

CREATE FUNCTION purgeHistoricalRecords
  "DELETE FROM Logs WHERE date < ( sysdate() - 31536000000 )"
  LANGUAGE SQL

Via Java API

OFunction func = db.getMetadata().getFunctionLibrary().createFunction("purgeHistoricalRecords");
func.setLanguage("SQL");
func.setCode("DELETE FROM Logs WHERE date < ( sysdate() - 31536000000 )");
func.save();
return func;

2) Schedule the event

The second step is scheduling the event. The CRON expression for "every midnight" is 00 00 * * * ?. You can this via SQL or Java API.

Via SQL

INSERT INTO oschedule
 SET name = 'purgeHistoricalRecordsAtMidnight',
     function = (SELECT FROM ofunction WHERE name = 'purgeHistoricalRecords'),
     rule = \"00 00 * * * ?\"

Via Java API

db.command(new OCommandSQL(
 "INSERT INTO oschedule SET name = 'purgeHistoricalRecordsAtMidnight', function = ?, rule = \"00 00 * * * ?\""))
 .execute(func.getId());