When the option "drop indexes" is in use in loading data from a file, we
collect the indexes from the PostgreSQL catalogs and then issue DROP
commands against them before the load, then CREATE commands when it's
done.
The CREATE is done in parallel, and we create an lparallel kernel for
that. The kernel must have a worker-count of at least 1, and we where
not considering the case of 0 indexes on the target table.
Fix#484.
More than the syntax and API tweaks, this patch also make it so that a
multi-file specification (using e.g. ALL FILENAMES IN DIRECTORY) can be
loaded with several files in the group in parallel.
To that effect, tweak again the md-connection and md-copy
implementations.
With this the user is now able to have a way about where the files are
going to be read and matched against the regular expression. It used not
to be necessary in the archive expansion mode, but is required now that
the feature is exposed in more cases.
When using LOAD CSV it's possible to load from filename matching a
regular expression, but for that to work the *csv-path-root* needs to be
properly setup at run-time.
