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.
* clarify that cannot show create table of system's tables
* clarify that cannot show create table of system's tables in the document
* bypass test style-check for required `database=currentDatabase()` because `show create table` do not have condition
* rename supportsShowCreateTable to isSystemStorage
* build fake create query for show create table of system's tables
* fix tests for show create table on system's table:
1. only build fake create query when cannot get real query
2. only test rocksdb when it's enabled.
* fix test for show create table system.tables
* fix test for ASTCreateQuery set table and database
* change to LOGICAL_ERROR when cannot get in_memory metadata
Co-authored-by: tavplubix <tavplubix@gmail.com>
* implement common getCreateQueryFromStorage
Co-authored-by: tavplubix <tavplubix@gmail.com>
