The links at the very beginning of
https://clickhouse.com/docs/en/sql-reference/statements/system
don't work. They are reference other sections of the same document. This
is weird because there is a small index already on the right side. I
searched our documentation and this seems to be the only pages which do
so. Therefore removing the links altogether instead of fixing them.
- This commit restores statements "SYSTEM RELOAD MODEL(S)" which provide
a mechanism to update a model explicitly. It also saves potentially
unnecessary reloads of a model from disk after it's initial load.
To keep the complexity low, the semantics of "SYSTEM RELOAD MODEL(S)
was changed from eager to lazy. This means that both statements
previously immedately reloaded the specified/all models, whereas now
the statements only trigger an unload and the first call to
catboostEvaluate() does the actual load.
- Monitoring view SYSTEM.MODELS is also restored but with some obsolete
fields removed. The view was not documented in the past and for now it
remains undocumented. The commit is thus not considered a breach of
ClickHouse's public interface.
- The deleted function modelEvaluate() was superseded by
catboostEvaluate().
- Also delete the external model repository, as modelEvaluate() was it's
last user. Additionally remove the system view SYSTEM.MODELS for
inspecting the repository.
- SYSTEM RELOAD MODELS is also obsolete. HOWEVER, it was retained and
made a no-op instead of deleted.
Why?
The reason is that RBAC in distributed setups works by storing
privileges (granted and revoked) as plain SQL statements in Keeper.
Nodes read these statements at startup and parse them. If a privilege
for SYSTEM RELOAD MODELS exists but parser doesn't recognize it
nodes would fail to come up.
Considered but rejected alternatives:
- Ignore SYSTEM RELOAD MODELS during parsing RBAC privileges and
return an error for regular SYSTEM RELOAD MODELS SQL. Special-case
of no-op behavior, too brittle.
- Remove SYSTEM RELOAD MODELS manually from Keeper via command-line
manipulation of Keeper nodes or via SQL by dropping the privileges.
Needs user intervention during upgrade.
Implementation:
- Added a new buffer ForkWriteBuffer takes a vector of WriteBuffer and writes data to all of them. It uses the buffer of the first element as its buffer and copies data from first buffer to all the other buffers
Testing:
- Updated tests/queries/0_stateless/02346_into_outfile_and_stdout.sh
Documentation:
- Updated the english documentation for SELECT.. INTO OUTFILE with AND STDOUT.
Implementation:
- Added a bool to ASTQueryWithOutput & patched the usage in ClientBase.
- Added a new buffer TeeWriteBuffer which extends from WriteBufferFromFile (used to write data to the file) and has WriteBufferFromFileDescriptor (used to write data to stdout). The WriteBufferFromFileDescriptor uses the same buffer as TeeWriteBuffer.
- Added a new bool select_into_outfile_and_stdout in ClientBase to enable/disable progress rendering.
Testing:
- Added a test tests/queries/0_stateless/02346_into_outfile_and_stdout.sh
Documentation:
- Updated the english documentation for the new option in SELECT.
