The decision to use lots of different packages in pgloader has quite
strong downsides at times, and the manual managment of dependencies is
one of the, in particular how to avoid circular ones.
In the recent refactoring and improvements of parallelism the indexes
creation would kick in before we know that the data is done being copied
over to the target table.
Fix that by maintaining a writers-count hashtable and only starting to
create indexes when that count reaches zero, meaning all the concurrent
tasks started to handle the COPY of the data are now done.
We convert the default value call to newsequentialid() into a call to
the PostgreSQL uuid-ossp uuid_generate_v1() which seems like the
equivalent function.
The extension "uuid-ossp" needs to be installed in the target database.
(Blind) Fix#246.
In order to share more code in between the different source types,
finally have a go at the quite horrible mess of anonymous data
structures floating around.
Having a catalog and schema instances not only allows for code cleanup,
but will also allow to implement some bug fixes and wishlist items such
as mapping tables from a schema to another one.
Also, supporting database sources having a notion of "schema" (in
between "catalog" and "table") should get easier, including getting
on-par with MySQL in the MS SQL support (materialized views has been
asked for already).
See #320, #316, #224 for references and a notion of progress being made.
In passing, also clean up the copy-databases methods for database source
types, so that they all use a fetch-metadata generic function and a
prepare-pgsql-database and a complete-pgsql-database generic function.
Actually, a single method does the job here.
The responsibility of introspecting the source to populate the internal
catalog/schema representation is now held by the fetch-metadata generic
function, which in turn will call the specialized versions of
list-all-columns and friends implementations. Once the catalog has been
fetched, an explicit CAST call is then needed before we can continue.
Finally, the fields/columns/transforms slots in the copy objects are
still being used by the operative code, so the internal catalog
representation is only used up to starting the data copy step, where the
copy class instances are then all that's used.
This might be refactored again in a follow-up patch.
