The documentation of functions
- parseDateTimeBestEffortUS(),
- parseDateTimeBestEffortUSOrNull() and
- parseDateTimeBestEffortUSOrZero()
previously repeated the text of functions
- parseDateTimeBestEffort(),
- parseDateTimeBestEffortOrNull() and
- parseDateTimeBestEffortOrZero().
In the docs of the first function, the duplication was removed and we
now emphasize the difference to the non-US version more clearly.
The docs of the second and third functions were just stripped of the
duplication. Chinese docs did not mention the US-date variants, hence
nothing was changed in them.
- In general, it is expected that clickhouse-*-bridges and
clickhouse-server were build from the same source version (e.g. are
upgraded "atomically"). If that is not the case, we should at least
be able to detect the mismatch and abort.
- This commit adds a URL parameter "version", defined in a header shared
by the server and bridges. The bridge returns an error in case of
mismatch.
- The version is *not* send and checked for "ping" requests (used for
handshake), only for regular requests send after handshake. This is
because the internally thrown server-side exception due to HTTP
failure does not propagate the exact HTTP error (it only stores the
error as text), and as a result, the server-side handshake code
simply retries in case of error with exponential backoff and finally
fails with a "timeout error". This is reasonable as pings typically
fail due to time out. However, without a rework of HTTP exceptions,
version mismatch during ping would also appear as "timeout" which is
too misleading. The behavior may be changed later if needed.
- Note that introducing a version parameter does not represent a
protocol upgrade itself. Bridges older than the server will simply
ignore the field. Only servers older than the bridges receive an error
but such a situation should never occur in practice.
- When catboost will be added into library-bridge later on, a lot of
code will need to be duplicated.
- Avoid that by factorizing stuff which is not specific to external
dictionaries for reuse into a common base class.
- This is a refactoring without semantic change.
