In case of underlying table has an ALIAS for this column, while in Merge
table it is not marked as an alias, there will NOT_FOUND_COLUMN_IN_BLOCK
error.
Further more, when underlying tables has different default type for the
column, i.e. one has ALIAS and another has real column, then you will
also get NOT_FOUND_COLUMN_IN_BLOCK, because Merge engine should take
care of this.
Also this patch reworks how PREWHERE is handled for Merge table, and now
if you use PREWHERE on the column that has the same type and default
type (ALIAS, ...) then it will be possible, and only if the type
differs, it will be prohibited and throw ILLEGAL_PREWHERE error.
And last, but not least, also respect this restrictions for
optimize_move_to_prewhere.
v2: introduce IStorage::supportedPrewhereColumns()
v3: Remove excessive condition for PREWHERE in StorageMerge::read()
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
- lots of static_cast
- add safe_cast
- types adjustments
- config
- IStorage::read/watch
- ...
- some TODO's (to convert types in future)
P.S. That was quite a journey...
v2: fixes after rebase
v3: fix conflicts after #42308 merged
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
The original motivation for this commit was that shared_ptr_helper used
std::shared_ptr<>() which does two heap allocations instead of
make_shared<>() which does a single allocation. Turned out that
1. the affected code (--> Storages/) is not on a hot path (rendering the
performance argument moot ...)
2. yet copying Storage objects is potentially dangerous and was
previously allowed.
Hence, this change
- removes shared_ptr_helper and as a result all inherited create() methods,
- instead, Storage objects are now created using make_shared<>() by the
caller (for that to work, many constructors had to be made public), and
- all Storage classes were marked as noncopyable using boost::noncopyable.
In sum, we are (likely) not making things faster but the code becomes
cleaner and harder to misuse.
