In PR #37300, Alexej asked why we the compiler does not warn about
unnecessary semicolons, e.g.
f()
{
}; // <-- here
The answer is surprising: In C++98, above syntax was disallowed but by
most compilers accepted it regardless. C++>11 introduced "empty
declarations" which made the syntax legal.
The previous behavior can be restored using flag
-Wc++98-compat-extra-semi. This finds many useless semicolons which were
removed in this change. Unfortunately, there are also false positives
which would require #pragma-s and HAS_* logic (--> check_flags.cmake) to
suppress. In the end, -Wc++98-compat-extra-semi comes with extra effort
for little benefit. Therefore, this change only fixes some semicolons
but does not enable the flag.
- Move some code into module part to avoid dependency from IStorage in SystemLog
- Remove extra headers from SystemLog.h
- Rewrite some code that was relying on headers that was included by SystemLog.h
v2: rebase
v3: squash move into module part with explicit template instantiation
(to make each commit self compilable after rebase)
TODO (suggested by Nikolai)
1. Build query plan fro current query (inside storage::read) up to WithMergableState
2. Check, that plan is simple enough: Aggregating - Expression - Filter - ReadFromStorage (or simplier)
3. Check, that filter is the same as filter in projection, and also expression calculates the same aggregation keys as in projection
4. Return WithMergableState if projection applies
3 will be easier to do with ActionsDAG, cause it sees all functions, and dependencies are direct (but it is possible with ExpressionActions also)
Also need to figure out how prewhere works for projections, and
row_filter_policies.
wip
