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Backport of ClickHouse/ClickHouse@a067567, re-created here rather than cherry-picked so that it carries a sign-off. The submodule tracked `apache/datasketches-cpp` directly, pinned to `76edd74f` (2024-05-16), an upstream development commit. It moves onto a `ClickHouse/`-prefixed branch of our fork, the way `docs/development/contrib` asks: ClickHouse/datasketches-cpp, branch ClickHouse/5.2.0 de8553ba 5.2.0, the newest upstream release (2025-01-15) 23bd9b07 backport of apache/datasketches-cpp#512 apache/datasketches-cpp#512 is the HyperLogLog union fix. No upstream release carries it, so it is cherry-picked onto the `5.2.0` tag there. `uniqApacheHLL`, added next, needs it: without it a merged HLL sketch reports a wrong estimate and serializes a state that other DataSketches implementations read differently. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: UnamedRus <dtitmoav@gmail.com>
…tion
Ported from `vk/uniq-apache-hll` (github.com/UnamedRus/ClickHouse), which develops the
function against `master`.
`uniqApacheHLL` counts distinct values into an Apache DataSketches HLL sketch, and its
`-State` serializes that sketch in the DataSketches format, so states can be exchanged
with Java, Python and C++ services through the standard `-State`/`-Merge` combinators.
Only the argument types those libraries hash the same way are accepted - integers of at
most 64 bits, Enum8/16, BFloat16, Float32/64, String, FixedString, UUID, IPv4, IPv6,
Date, Date32, DateTime and DateTime64 - so no state can be built here that an external
consumer cannot reproduce.
Two deviations from the branch this is taken from, both forced by the age of this base:
- the state overrides `merge`, not `mergeImpl`. `IAggregateFunction::merge` is still
the pure virtual here; the split into a non-virtual `merge` plus a `mergeImpl`
override came later.
- `introduced_in` says 26.6 rather than 26.9, this being the release it ships in.
NOT BUILT OR TESTED on this base - only ported and checked by inspection against the
26.6 headers. CI is the first real build.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: UnamedRus <dtitmoav@gmail.com>
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Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):
Aggregate function, which states are compatible with apache data sketches HLL implementation