quoted `current_schema` is literally a schema name and must
but treated as such. because Sql_path stores all names unquoted
let's store the current_schema as an empty name, length=0.
No valid schema name can be empty.
because it's always allocated and freed as a whole, there is
no operation "replace one name in the middle of the path"
this needed a reworked parser to create the whole list
of names, not append one name at a time.
Fixed a bug where Sql_path::from_text() pretended it can take
a string in any charset, but was always implicitly
assuming it's in my_charset_utf8mb3_general_ci.
* rename to follow the standard vprintf name convention
* remove `(LEX_CSTRING*) &lex_string` casts
* remove some redundant casts too
* LEX_CSTRING -> Lex_ident_db in path
* Hash_set<Sroutine_hash_entry>
* move assert out of the loop
* some comments and whitespace changes
don't create a permanent stack of paths on the heap and in THD.
Do it on the stack like for sql_mode, sctx, abort_on_warning, and
other THD properties that often need to be changed temporarily.
Fix Sql_path constructor.
Definition
==========
Implement the SET PATH statement.
```
SET PATH 'schema1, schema2, schema3';
```
Function
--------
In MariaDB, the SQL-path will also be used to lookup packages in
package routine invocations, so the following script:
SET PATH 'sys';
SELECT UTL_ENCODE.BASE64_DECODE('data');
invokes SYS.UTL_ENCODE.BASE64_DECODE('data'), i.e. the function
BASE64_DECODE() in the packge UTL_ENCODE in the database SYS
(if such package and package routine exist).
MariaDB implementation details
------------------------------
The ticket's requirement stated the grammar should support delimited
identifiers with backticks or double quotes within the string quote,
ie: the single tick. A simple parser was implemented to handle this
requirement in Sql_path::from_text.
Only 16 schemas are supported per session - we do not want too many
schemas in the path anyway since it will impact performance. This also
means that the path cache is a simple static array for easier memory
management.
