cf5d7ce212
Scylla's materialized views naturally skip any base rows where the view's
key isn't set (is NULL), because we can't create a view row with a null
key. To make the user aware that this is happening, the user is required
to add "WHERE ... IS NOT NULL" for the view's key columns when defining
the view. However, the only place that these extra IS NOT NULL clauses
are checked are in the CQL "CREATE MATERIALIZED VIEWS" statement - they
are completely ignored in all other places in the code.
In particular, when we create a materialized view in Alternator (GSI or
LSI), we don't have to add these "IS NOT NULL" clauses, as they are
outright ignored. We didn't know they were ignored, and made an effort
to add them - but no matter how incorrectly we did it, it didn't matter :-)
In commit 2bf2ffd3ed it turned out we had a
typo that caused the wrong column name to be printed. Also, even today we
are still missing base key columns that aren't listed as a view key in
Alternator but still added as view clustering keys in Scylla - and again
the fact these were missing also didn't matter. So I think it's time to
stop pretending, and stop calculating these "IS NOT NULL" strings, so
this patch outright removes them from the Alternator view-creation code.
Beyond being a nice cleanup of unnecessary and inaccurate code, it
will also be necessary when we allow in later patches to index for
an Alternator attribute "x" not a real column x in the base table but
rather an element in the ":attrs" map - so adding a "x IS NOT NULL" isn't
only unnecessary, it is outright illegal: The expression evaluation code,
even though it doesn't do anything with the "IS NOT NULL" expression,
still verifies that "x" is a valid column, which it isn't.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Scylla
What is Scylla?
Scylla is the real-time big data database that is API-compatible with Apache Cassandra and Amazon DynamoDB. Scylla embraces a shared-nothing approach that increases throughput and storage capacity to realize order-of-magnitude performance improvements and reduce hardware costs.
For more information, please see the ScyllaDB web site.
Build Prerequisites
Scylla is fairly fussy about its build environment, requiring very recent versions of the C++23 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers a frozen toolchain, This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).
Building Scylla
Building Scylla with the frozen toolchain dbuild is as easy as:
$ git submodule update --init --force --recursive
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
For further information, please see:
- Developer documentation for more information on building Scylla.
- Build documentation on how to build Scylla binaries, tests, and packages.
- Docker image build documentation for information on how to build Docker images.
Running Scylla
To start Scylla server, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --workdir tmp --smp 1 --developer-mode 1
This will start a Scylla node with one CPU core allocated to it and data files stored in the tmp directory.
The --developer-mode is needed to disable the various checks Scylla performs at startup to ensure the machine is configured for maximum performance (not relevant on development workstations).
Please note that you need to run Scylla with dbuild if you built it with the frozen toolchain.
For more run options, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --help
Testing
See test.py manual.
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its API - CQL. There is also support for the API of Amazon DynamoDB™, which needs to be enabled and configured in order to be used. For more information on how to enable the DynamoDB™ API in Scylla, and the current compatibility of this feature as well as Scylla-specific extensions, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found here. Seastar documentation can be found here. User documentation can be found here.
Training
Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.
Contributing to Scylla
If you want to report a bug or submit a pull request or a patch, please read the contribution guidelines.
If you are a developer working on Scylla, please read the developer guidelines.
Contact
- The community forum and Slack channel are for users to discuss configuration, management, and operations of the ScyllaDB open source.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.