New query style for obsdb which enables to use external database

[tterasaki]

new query style for obsdb which enables to use external database.

[tterasaki]

I think it is ready to go.

[mhasself]

This is neat! I want to experiment with it a bit more. The docstring details are appreciated but can you add some basic tests?

[tterasaki]

Thank you, Matthew.
If you want to test or play around, you can use:
computeXX: /so/metadata/satp1/manifests/pwv_class/satp1_pwv_class_240516m/pwv_class.sqlite

[mhasself]

Sorry it took me so long to get to this. This is a really useful capability to have!

My requests for now are:

• deal with too-long lines (marked inline)
• squash and rebase

In the longer term I think we should update the interface so that:

• Extend ObsDb so that 'attach' can occur on the base ObsDb object, allowing access to merged fields in any request (including .get), without passing subdb_info to each call
• Extent Context so it can attach obsdb extensions automatically.
• Include more description of this feature in the docs.

But we don't need to deal with that stuff now.

[mhasself]

Line too long; use \

[mhasself]

Please reduce line lengths here.

You could pass **subdb_info instead of all these .get(...)?

[mhasself]

sotodlib.core

[davidvng]

In combination with #850, I added handling for querying an external ManifestDB in which a field, in this case coverage has a string value that is a list comma-separated strings in SQLite format. I added the translation of the query '<substring> in coverage' to become 'coverage LIKE "%<substring>%"' to be understood by SQL as "any string that contains this substring"
I added a test to the test script and also tested on a real ManifestDB I created from #850
In that database there is the following entry:

[{'_id': 1,
  'filename': 'preprocess_obs_sourcetags_archive_v2.h5',
  'obs:obs_id': 'obs_1721381147_satp1_1111111',
  'dataset': 'obs_1721381147_satp1_1111111',
  'coverage': 'saturn:ws0,saturn:ws4,saturn:ws5,neptune:ws4,neptune:ws5,QSO_J2253+1608:ws5'}]

I can successfully retrieve that entry with the following query:

r0 = obsdb.query(
                    subdbs_info_list = [{'filepath': extdb_path,
                                         'query_list': ['saturn:ws0 in coverage'],
                                         'params_list': ['coverage']}]
                   )

[mhasself]

Hi @davidvng and @tterasaki -- who is going to deal with my requested changes to the original PR?

@davidvng On the "coverage" changes -- those seem fine but you need to clean up the testing function (remove prints, restore mpi check).