In principle it would be better if the qc information were
obtained via a specific query_classifier resource. However,
there are multiple problems with that (e.g. the qc has no way
of safely accessing information of another thread) and hence
the worker specific qc cache statistics is reported as part of
the worker statistics.
The cache now enforces the defined maximum size by evicting some
entries in case the insertion of a new entry would cause the max
size to be exceeded. Currently the eviction algorithm simply
removes a random element.
With the global configuration parameter 'query_classifier_cache'
the query classification cache can be turned on. At the moment it
does not matter what value it has; its presence simply enables the
caching.
Eventually you will be able to specify how much memory the cache
is allowed to consume.
Now takes a structure that, if present, enables the query
classification caching and specifies the properties of the
cache.
For the time being no actual properties are yet available.
The sql mode affects the result of the query classification.
Consequently, we cannot use the cached result if it was generated
when the sql mode was something else than what it currently is.
The mapping from a canonical statement to the query classification
result is maintained by the class QCInfoCache of which there exist
an instance per thread. That way no locking is needed but the
information will be cached multiple times (but that is a smaller
price to pay). Currently the information is stored in a regular
std::unordered_map, which means that the consumed amount of
memory will just keep on growing unless the number of canonical
statements used by clients happens to have an upper bound.
The LRU cache (that provides means for putting a bound on the
amount of memory used and number of items) used in the cache filter
will be generalized and be taken into use here as well.
The key is now the canonical statement itself, which means that
a fair amount of memory will be used. To preserve memory it might
make sense to use a hashed value instead, although that at least
in principle opens up the possibility for unintended collisions.
This feature will also be made configurable.
Minor cleanup:
- Unit variables places in anonymous namespace.
- Unit variables accessed via this_unit struct.
This is the first commit of many where the mapping from canonical
statement to query classification result is introduced.
The mapping is placed above the actual query classifier, so that all
query classifiers will benefit from it.
The mapping will be maintained by thread so that there will not be
any synchronization issues. Further, initially a simple map without
upper boundary will be used; if this is found to provide measurable
benefits, the map will then be replaced with an LRU mechanism so
that it becomes possible to specify just how much memory the mapping
may use.
The two operations return different types of results and need to be
treated differently in order for them to be handled correctly in 2.2.
This fixes the unexpected internal state errors that happened in all 2.2
versions due to a wrong assumption made by readwritesplit. This fix is not
necessary for newer versions as the LOAD DATA LOCAL INFILE processing is
done with a simpler, and more robust, method.
The internal header directory conflicted with in-source builds causing a
build failure. This is fixed by renaming the internal header directory to
something other than maxscale.
The renaming pointed out a few problems in a couple of source files that
appeared to include internal headers when the headers were in fact public
headers.
Fixed maxctrl in-source builds by making the copying of the sources
optional.
Basically it would be trivial to report far more operations
explicitly, but for the fact that the values in qc_query_op_t
currently, quite unnecessarily, form a bitmask.
In 2.2 that is no longer the case, so other operations will be
added there.
It is now possible to specify what information the caller is interested
in. With this the cost for collecting information during the query parsing
that nobody is interested in can be avoided.
For the general case, regex matching simply will not do. The
regex becomes so hairy so it turns write-only, i.e. unmaintainable.
Regex matching is also slower than a handwritten custom parser.
