The PostgreSQL search_path allows multiple schemas and might even need
it to be able to reference types and other tables. Allow setting more
than one schema by using the fact that PostgreSQL schema names don't
need to be individually quoted, and passing down the exact content of
the SET search_path value down to PostgreSQL.
Fix#359.
The new ALTER TABLE facility allows to act on tables found in the MySQL
database before the migration happens. In this patch the only provided
actions are RENAME TO and SET SCHEMA, which fixes#224.
In order to be able to provide the same option for MS SQL users, we will
have to make it work at the SCHEMA level (ALTER SCHEMA ... RENAME TO
...) and modify the internal schema-struct so that the schema slot of
our table instances are a schema instance rather than its name.
Lacking MS SQL test database and instance, the facility is not yet
provided for that source type.
Add the workers and concurrency settings to the LOAD commands for
database sources so that users can tweak them now, and add mentions of
them in the documentation too.
From the documentation string of the copy-from method as found in
src/sources/common/methods.lisp:
We allow WORKER-COUNT simultaneous workers to be active at the same time
in the context of this COPY object. A single unit of work consist of
several kinds of workers:
- a reader getting raw data from the COPY source with `map-rows',
- N transformers preparing raw data for PostgreSQL COPY protocol,
- N writers sending the data down to PostgreSQL.
The N here is setup to the CONCURRENCY parameter: with a CONCURRENCY of
2, we start (+ 1 2 2) = 5 concurrent tasks, with a CONCURRENCY of 4 we
start (+ 1 4 4) = 9 concurrent tasks, of which only WORKER-COUNT may be
active simultaneously.
Those options should find their way in the remaining sources, that's for
a follow-up patch tho.
The default values for MySQL WITH clause options wasn't really tested
and broke on simple cases, the new set of defaults is known to work in
many cases (most?).
Other combinations of options will need some review work, and we might
need to consider preventing some of them, that's for another patch tho.
