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Ignite Rollup

Overview

A very common pattern that we see with many clients, is that data is fed into an Apache Ignite or GridGain cluster into two tables: one is the full data, the second is a summary, or rollup, of that data.

With GridGain’s SQL engine, it’s not always necessary to have a summary table at all! For many, perhaps most, use cases, the fact that the data is held in memory and distributed efficiently means that even a complex “group by” expression can be performed very quickly.

However, when the lowest latency is required, performing those aggregations dynamically is not going to cut it. Here we typically “pre-aggregate” the data, creating a summary table that can be queried directly.

This is a demo project showing a couple of ways you might implement that.

How to run

It's designed to run on your local machine, in an IDE. It'll need some minor changes to run on "real" servers.

  1. Run RollupServer. You can run several copies of this. If you add -DIGNITE_QUIET=false you'll see more logging
  2. Run RollupClient. This will create the tables and deploy the rollup services
  3. Connect using a JDBC client and insert some records
0: jdbc:ignite:thin://127.0.0.1> insert into base.rollupvalue values (1,1,1);
1 row affected (0.073 seconds)
0: jdbc:ignite:thin://127.0.0.1> insert into base.rollupvalue values (2,2,1);
1 row affected (0.003 seconds)
0: jdbc:ignite:thin://127.0.0.1> insert into base.rollupvalue values (3,2,2);
1 row affected (0.002 seconds)
0: jdbc:ignite:thin://127.0.0.1> select * from rollup.rollupvalue;
+--------------------------------+--------------------------------+--------------------------------+
|               ID               |           FOREIGNKEY           |             VALUE              |
+--------------------------------+--------------------------------+--------------------------------+
| 2                              | 2                              | 3                              |
| 1                              | 1                              | 1                              |
| 2                              | 1                              | 3                              |
| 1                              | 2                              | 1                              |
+--------------------------------+--------------------------------+--------------------------------+
4 rows selected (0.009 seconds)
  1. See what happens

Description

  • EventRollupServiceImpl. Listens to the base table using a Continuous Query. Updates the summary table immediately
  • TimedRollupServiceImpl. Periodically executed a SQL query to generate the summary

See the blog for a more detailed description.