Sorry for the clickbaity title. This is about static method
ConnectionTimeouts::getHTTPTimeouts(). It was be declared in header
IO/ConnectionTimeouts.h, and defined in header
IO/ConnectionTimeoutsContext.h (!). This is weird and caused issues with
linking on s390x (##45520). There was an attempt to fix some
inconsistencies (#45848) but neither did @Algunenano nor me at first
really understand why the definition is in the header.
Turns out that ConnectionTimeoutsContext.h is only #include'd from
source files which are part of the normal server build BUT NOT part of
the keeper standalone build (which must be enabled via CMake
-DBUILD_STANDALONE_KEEPER=1). This dependency was not documented and as
a result, some misguided workarounds were introduced earlier, e.g.
0341c6c54b
The deeper cause was that getHTTPTimeouts() is passed a "Context". This
class is part of the "dbms" libary which is deliberately not linked by
the standalone build of clickhouse-keeper. The context is only used to
read the settings and the "Settings" class is part of the
clickhouse_common library which is linked by clickhouse-keeper already.
To resolve this mess, this PR
- creates source file IO/ConnectionTimeouts.cpp and moves all
ConnectionTimeouts definitions into it, including getHTTPTimeouts().
- breaks the wrong dependency by passing "Settings" instead of "Context"
into getHTTPTimeouts().
- resolves the previous hacks
* save format string for NetException
* format exceptions
* format exceptions 2
* format exceptions 3
* format exceptions 4
* format exceptions 5
* format exceptions 6
* fix
* format exceptions 7
* format exceptions 8
* Update MergeTreeIndexGin.cpp
* Update AggregateFunctionMap.cpp
* Update AggregateFunctionMap.cpp
* fix
Reasons:
1. The original Gorilla paper proposed a compression schema for pairs of
time stamps and double-precision FP values. ClickHouse's Gorilla
codec only implements compression of the latter and it does not
impose any data type restrictions.
- Data types != Float* or (U)Int* (e.g. Decimal, Point etc.) are
definitely not supposed to be used with Gorilla.
- (U)Int* types are debatable. The paper only considers
integers-stored-as-FP-values, a practical use case for which
Gorilla works well. Standalone integers are not considered which
makes them at least suspicious.
2. Achieve consistency with FPC, another specialized floating-point
timeseries codec, which rejects non-float data.
3. On practical datasets, ZSTD is often "good enough" (**) so it should
be okay to disincentive non-ZSTD codecs a little bit. If needed,
Delta and DoubleDelta codecs are viable alternative for slowly
changing (time-series-like) integer sequences.
Since on-prem and hosted users may still have Gorilla-compressed
non-float data, this combination is only deprecated for now. No warning
or error will be emitted. Users are encouraged to migrate
Gorilla-compressed non-float data to an alternative codec. It is planned
to treat Gorilla-compressed non-float columns as "suspicious" six months
after this commit (i.e. in v23.6). Even then, it will still be possible
to set "allow_suspicious_codecs = true" and read and write
Gorilla-compressed non-float data.
(*) Sec. 4.1.2, "Gorilla restricts the value element in its tuple to a
double floating point type.", https://doi.org/10.14778/2824032.2824078
(**) https://clickhouse.com/blog/optimize-clickhouse-codecs-compression-schema
