efed973dd3
LWT `IF` (column_condition) duplicates the expression prepare and evaluation code. Annoyingly, LWT IF semantics are a little different than the rest of CQL: a NULL equals NULL, whereas usually NULL = NULL evaluates to NULL. This series converts `IF` prepare and evaluate to use the standard expression code. We employ expression rewriting to adjust for the slightly different semantics. In a few places, we adjust LWT semantics to harmonize them with the rest of CQL. These are pointed out in their own separate patches so the changes don't get lost in the flood. Closes #12356 * github.com:scylladb/scylladb: cql3: lwt: move IF clause expression construction to grammar cql3: column_condition: evaluate column_condition as a single expression cql3: lwt: allow negative list indexes in IF clause cql3: lwt: do not short-circuit col[NULL] in IF clause cql3: column_condition: convert _column to an expression cql3: expr: generalize evaluation of subscript expressions cql3: expr: introduce adjust_for_collection_as_maps() cql3: update_parameters: use evaluation_inputs compatible row prefetch cql3: expr: protect extract_column_value() from partial clustering keys cql3: expr: extract extract_column_value() from evaluation machinery cql3: selection: introduce selection_from_partition_slice cql3: expr: move check for ordering on duration types from restrictions to prepare cql3: expr: remove restrictions oper_is_slice() in favor of expr::is_slice() cql3: column_condition: optimize LIKE with constant pattern after preparing cql3: expr: add optimizer for LIKE with constant pattern test: lib: add helper to evaluate an expression with bind variables but no table cql3: column_condition: make the left-hand-side part of column_condition::raw cql3: lwt: relax constraints on map subscripts and LIKE patterns cql3: expr: fix search_and_replace() for subscripts cql3: expr: fix function evaluation with NULL inputs cql3: expr: add LWT IF clause variants of binary operators cql3: expr: change evaluate_binop_sides to return more NULL information
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.