ClickHouse/docs/en/development/contrib.md

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70	Third-Party Libraries Used

Third-Party Libraries Used

The list of third-party libraries can be obtained by the following query:

SELECT library_name, license_type, license_path FROM system.licenses ORDER BY library_name COLLATE 'en';

Example

library_name	license_type	license_path
abseil-cpp	Apache	/contrib/abseil-cpp/LICENSE
AMQP-CPP	Apache	/contrib/AMQP-CPP/LICENSE
arrow	Apache	/contrib/arrow/LICENSE.txt
avro	Apache	/contrib/avro/LICENSE.txt
aws	Apache	/contrib/aws/LICENSE.txt
aws-c-common	Apache	/contrib/aws-c-common/LICENSE
aws-c-event-stream	Apache	/contrib/aws-c-event-stream/LICENSE
aws-checksums	Apache	/contrib/aws-checksums/LICENSE
base64	BSD 2-clause	/contrib/base64/LICENSE
boost	Boost	/contrib/boost/LICENSE_1_0.txt
boringssl	BSD	/contrib/boringssl/LICENSE
brotli	MIT	/contrib/brotli/LICENSE
capnproto	MIT	/contrib/capnproto/LICENSE
cassandra	Apache	/contrib/cassandra/LICENSE.txt
cctz	Apache	/contrib/cctz/LICENSE.txt
cityhash102	MIT	/contrib/cityhash102/COPYING
cppkafka	BSD 2-clause	/contrib/cppkafka/LICENSE
croaring	Apache	/contrib/croaring/LICENSE
curl	Apache	/contrib/curl/docs/LICENSE-MIXING.md
cyrus-sasl	BSD 2-clause	/contrib/cyrus-sasl/COPYING
double-conversion	BSD 3-clause	/contrib/double-conversion/LICENSE
dragonbox	Apache	/contrib/dragonbox/LICENSE-Apache2-LLVM
fast_float	Apache	/contrib/fast_float/LICENSE
fastops	MIT	/contrib/fastops/LICENSE
flatbuffers	Apache	/contrib/flatbuffers/LICENSE.txt
fmtlib	Unknown	/contrib/fmtlib/LICENSE.rst
gcem	Apache	/contrib/gcem/LICENSE
googletest	BSD 3-clause	/contrib/googletest/LICENSE
grpc	Apache	/contrib/grpc/LICENSE
h3	Apache	/contrib/h3/LICENSE
hyperscan	Boost	/contrib/hyperscan/LICENSE
icu	Public Domain	/contrib/icu/icu4c/LICENSE
icudata	Public Domain	/contrib/icudata/LICENSE
jemalloc	BSD 2-clause	/contrib/jemalloc/COPYING
krb5	MIT	/contrib/krb5/src/lib/gssapi/LICENSE
libc-headers	LGPL	/contrib/libc-headers/LICENSE
libcpuid	BSD 2-clause	/contrib/libcpuid/COPYING
libcxx	Apache	/contrib/libcxx/LICENSE.TXT
libcxxabi	Apache	/contrib/libcxxabi/LICENSE.TXT
libdivide	zLib	/contrib/libdivide/LICENSE.txt
libfarmhash	MIT	/contrib/libfarmhash/COPYING
libgsasl	LGPL	/contrib/libgsasl/LICENSE
libhdfs3	Apache	/contrib/libhdfs3/LICENSE.txt
libmetrohash	Apache	/contrib/libmetrohash/LICENSE
libpq	Unknown	/contrib/libpq/COPYRIGHT
libpqxx	BSD 3-clause	/contrib/libpqxx/COPYING
librdkafka	MIT	/contrib/librdkafka/LICENSE.murmur2
libunwind	Apache	/contrib/libunwind/LICENSE.TXT
libuv	BSD	/contrib/libuv/LICENSE
llvm	Apache	/contrib/llvm/llvm/LICENSE.TXT
lz4	BSD	/contrib/lz4/LICENSE
mariadb-connector-c	LGPL	/contrib/mariadb-connector-c/COPYING.LIB
miniselect	Boost	/contrib/miniselect/LICENSE_1_0.txt
msgpack-c	Boost	/contrib/msgpack-c/LICENSE_1_0.txt
murmurhash	Public Domain	/contrib/murmurhash/LICENSE
NuRaft	Apache	/contrib/NuRaft/LICENSE
openldap	Unknown	/contrib/openldap/LICENSE
orc	Apache	/contrib/orc/LICENSE
poco	Boost	/contrib/poco/LICENSE
protobuf	BSD 3-clause	/contrib/protobuf/LICENSE
rapidjson	MIT	/contrib/rapidjson/bin/jsonschema/LICENSE
re2	BSD 3-clause	/contrib/re2/LICENSE
replxx	BSD 3-clause	/contrib/replxx/LICENSE.md
rocksdb	BSD 3-clause	/contrib/rocksdb/LICENSE.leveldb
s2geometry	Apache	/contrib/s2geometry/LICENSE
sentry-native	MIT	/contrib/sentry-native/LICENSE
simdjson	Apache	/contrib/simdjson/LICENSE
snappy	Public Domain	/contrib/snappy/COPYING
sparsehash-c11	BSD 3-clause	/contrib/sparsehash-c11/LICENSE
stats	Apache	/contrib/stats/LICENSE
thrift	Apache	/contrib/thrift/LICENSE
unixodbc	LGPL	/contrib/unixodbc/COPYING
xz	Public Domain	/contrib/xz/COPYING
zlib-ng	zLib	/contrib/zlib-ng/LICENSE.md
zstd	BSD	/contrib/zstd/LICENSE

Guidelines for adding new third-party libraries and maintaining custom changes in them

1. All external third-party code should reside in the dedicated directories under contrib directory of ClickHouse repo. Prefer Git submodules, when available.
2. Fork/mirror the official repo in Clickhouse-extras. Prefer official GitHub repos, when available.
3. Branch from the branch you want to integrate, e.g., master -> clickhouse/master, or release/vX.Y.Z -> clickhouse/release/vX.Y.Z.
4. All forks in Clickhouse-extras can be automatically synchronized with upstreams. clickhouse/... branches will remain unaffected, since virtually nobody is going to use that naming pattern in their upstream repos.
5. Add submodules under contrib of ClickHouse repo that refer the above forks/mirrors. Set the submodules to track the corresponding clickhouse/... branches.
6. Every time the custom changes have to be made in the library code, a dedicated branch should be created, like clickhouse/my-fix. Then this branch should be merged into the branch, that is tracked by the submodule, e.g., clickhouse/master or clickhouse/release/vX.Y.Z.
7. No code should be pushed in any branch of the forks in Clickhouse-extras, whose names do not follow clickhouse/... pattern.
8. Always write the custom changes with the official repo in mind. Once the PR is merged from (a feature/fix branch in) your personal fork into the fork in Clickhouse-extras, and the submodule is bumped in ClickHouse repo, consider opening another PR from (a feature/fix branch in) the fork in Clickhouse-extras to the official repo of the library. This will make sure, that 1) the contribution has more than a single use case and importance, 2) others will also benefit from it, 3) the change will not remain a maintenance burden solely on ClickHouse developers.
9. When a submodule needs to start using a newer code from the original branch (e.g., master), and since the custom changes might be merged in the branch it is tracking (e.g., clickhouse/master) and so it may diverge from its original counterpart (i.e., master), a careful merge should be carried out first, i.e., master -> clickhouse/master, and only then the submodule can be bumped in ClickHouse.