14e13ecbd4
This is a backport of https://github.com/scylladb/scylla/pull/10420 to branch 5.0.
Branch 5.0 had somewhat different code in this expression area, so the backport was not automatically, but nevertheless was fairly straightforward - just copy the exact same checking code to its right place, and keep the exact same tests to see we indeed fixed the bug.
Refs #10535.
The original cover letter from https://github.com/scylladb/scylla/pull/10420:
In the filtering expression "WHERE m[?] = 2", our implementation was buggy when either the map, or the subscript, was NULL (and also when the latter was an UNSET_VALUE). Our code ended up dereferencing null objects, yielding bizarre errors when we were lucky, or crashes when we were less lucky - see examples of both in issues https://github.com/scylladb/scylla/issues/10361, https://github.com/scylladb/scylla/issues/10399, https://github.com/scylladb/scylla/pull/10401. The existing test test_null.py::test_map_subscript_null reproduced all these bugs sporadically.
In this series we improve the test to reproduce the separate bugs separately, and also reproduce additional problems (like the UNSET_VALUE). We then define both m[NULL] and NULL[2] to result in NULL instead of the existing undefined (and buggy, and crashing) behavior. This new definition is consistent with our usual SQL-inspired tradition that NULL "wins" in expressions - e.g., NULL < 2 is also defined as resulting in NULL.
However, this decision differs from Cassandra, where m[NULL] is considered an error but NULL[2] is allowed. We believe that making m[NULL] be a NULL instead of an error is more consistent, and moreover - necessary if we ever want to support more complicate expressions like m[a], where the column a can be NULL for some rows and non-NULL for others, and it doesn't make sense to return an "invalid query" error in the middle of the scan.
Fixes https://github.com/scylladb/scylla/issues/10361
Fixes https://github.com/scylladb/scylla/issues/10399
Fixes https://github.com/scylladb/scylla/pull/10401
Closes #11142
* github.com:scylladb/scylla:
test/cql-pytest: reproducer for CONTAINS NULL bug
expressions: don't dereference invalid map subscript in filter
expressions: fix invalid dereference in map subscript evaluation
test/cql-pytest: improve tests for map subscripts and nulls
(cherry picked from commit 23a34d7e42)
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++20 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 APIs - CQL and Thrift. 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 users mailing list 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.