Entries tagged [memory]

Thursday April 28, 2022

Apache Ignite 2.13.0: new Apache Calcite-based SQL engine

As of April 26, 2022, Apache Ignite 2.13 has been released. You can directly check the full list of resolved Important JIRA tasks but here let's briefly overview some valuable improvements.

This is a breaking change release: The legacy service grid implementation was removed.

New Apache Calcite-based SQL engine

We've implemented a new experimental SQL engine based on Apache Calcite. Now it's possible to:

The current H2-based engine has fundamental limitations. For example:

  • some queries should be splitted into 2 phases (map subquery and reduce subquery), but some of them cannot be effectively executed in 2 phases.
  • H2 is a third-party database product with not-ASF license.
  • The optimizer and other internal things are not supposed to work in a distributed environment.
  • It's hard to make Ignite-specific changes to the H2 code, patches are often declined.

The Apache Calcite is a SQL engine with customizable modules. Requests can be splitted into more than 2 phases.

A query engine can be set before query execution. Here is an example for SQL:

SELECT /*+ QUERY_ENGINE('h2') */ fld FROM table;
or
SELECT /*+ QUERY_ENGINE('calcite') */ fld FROM table;

See JDBC and ODBC examples here.

The new engine requires the ignite-indexing module (which depends on H2) to be included to the classpath to support queries infrastructure.

See more technical details about the new engine in the IEP-37.

Read Repair strategies

"Read Repair" refers to a technique of repairing inconsistencies between primary and backup copies of data during normal read operations. When a specific key (or keys) is read by a user operation, Ignite checks the values for the given key in all backup copies.

We've implemented the new Read Repair strategies as follows:

  • LWW (Last Write Wins) - Last write (the newest entry) wins.
  • PRIMARY - Value from the primary node wins.
  • RELATIVE_MAJORITY - The relative majority: a value found more often than any other wins.
  • REMOVE - Inconsistent entries will be removed.
  • CHECK_ONLY - Only check will be performed.

Array type in Binary Object

In previous versions Ignite did not save information about array type. Now it can be stored in a binary object:

cache.put(1, new Person[] {new Person(1), new Person(2)});

Person[] obj = cache.get(1);

assertEquals(Person[].class, obj.getClass());

The feature is disabled by default due to compatibility issues. Set the IGNITE_USE_BINARY_ARRAYS system property to true to enable it.

CDC for in-memory caches

The Change Data Capture now can be configured for in-memory caches. From now on, only CDC needed records for such caches will be logged to WAL.

Other improvements and changes

  • The C++ thin client implemented continuous queries and asynchronous network events handling. See the updated thin clients features list here;
  • Implemented NUMA-aware allocator for data regions;
  • Ignite maven BOM;
  • Removed the legacy service grid implementation;
  • 100+ small improvements and bug fixes.

Anything else?

See the release notes to learn about all of the new features and improvements.

Reach out to us on the community user list for more questions, details, and feedback.

Sincerely yours, Ignite contributors and committers

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