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When generating CDC log mutations for some base mutation, use a CDC schema that is compatible with the base schema. The compatible CDC schema has for every base column a corresponding CDC column with the same name. If using a non-compatible schema, we may encounter a situation, especially during ALTER, that we have a mutation with a base column set with some value, but the CDC schema doesn't have a column by that name. This would cause the user request to fail with an error. We add to the schema object a schema_ptr that for CDC-enabled tables points to the schema object of the CDC table that is compatible with the schema. It is set by the schema merge algorithm when creating the schema for a table that is created or altered. We use the fact that a base table and its CDC table are created and altered in the same group0 operation, and this way we can find and set the cdc schema for a base table. When transporting the base schema as a frozen schema between shards, we transport with it the frozen cdc schema as well. The patch starts with a series of refactoring commits that make extending the frozen schema easier and cleans up some duplication in the code about the frozen schema. We combine the two types `frozen_schema_with_base_info` and `view_schema_and_base_info` to a single type `extended_frozen_schema` that holds a frozen schema with additional data that is not part of the schema mutations but needs to be transported with it to unfreeze it - base_info, and the frozen cdc schema which is added in a later commit. Fixes https://github.com/scylladb/scylladb/issues/26405 backport not needed - enhancement Closes scylladb/scylladb#24960 * github.com:scylladb/scylladb: test: cdc: test cdc compatible schema cdc: use compatiable cdc schema db: schema_applier: create schema with pointer to CDC schema db: schema_applier: extract cdc tables schema: add pointer to CDC schema schema_registry: remove base_info from global_schema_ptr schema_registry: use extended_frozen_schema in schema load schema_registry: replace frozen_schema+base_info with extended_frozen_schema frozen_schema: extract info from schema_ptr in the constructor frozen_schema: rename frozen_schema_with_base_info to extended_frozen_schema
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 ScyllaDB.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.