distance_result no longer in votable_fields in Simbad.query_region

[havok2063]

Prior to 0.4.8 and #2954, distance_result was a valid votable field that returned the cone search separation distance in arcsec when doing a Simbad.query_region search. After 0.4.8, distance_result is no longer a valid field, and I cannot find what the equivalent field is. Is there a mapping available between the old votable fields and the new ones?

The PR mentions some column changes but the error message with distance_result isn't described in the PR. I also don't see anything in https://astroquery.readthedocs.io/en/latest/simbad/simbad_evolution.html. Now that Simbad.list_votable_fields() returns a mix of tables and columns, is there a way to list all the available columns from all tables?

0.4.7

import astropy.units as u
from astroquery.simbad import Simbad
from astropy.coordinates import SkyCoord

s = SkyCoord(*(230.50745896, 43.53232817), unit='deg')

Simbad.add_votable_fields('distance_result')
Simbad.add_votable_fields('ra(d)', 'dec(d)')

res = Simbad.query_region(s, radius=5*u.Unit('arcmin'))

res
<Table length=7>
          MAIN_ID                 RA           DEC      RA_PREC DEC_PREC ... DISTANCE_RESULT     RA_d        DEC_d     SCRIPT_NUMBER_ID
                               "h:m:s"       "d:m:s"                     ...      arcsec         deg          deg
           object               str13         str13      int16   int16   ...     float32       float64      float64         int32
--------------------------- ------------- ------------- ------- -------- ... --------------- ------------ ------------ ----------------
               LEDA 2223006 15 22 01.7901 +43 31 56.381      14       14 ...          0.0000 230.50745896  43.53232817                1
   SDSS J152148.52+433252.8  15 21 48.524  +43 32 52.89       7        7 ...        154.9247 230.45218200  43.54802500                1
    ZTF J152155.59+432835.3 15 21 55.6209 +43 28 35.186      14       14 ...        212.0959 230.48175387  43.47644056                1
             TYC 3058-345-1 15 22 25.5363 +43 30 46.098      14       14 ...        267.6688 230.60640150  43.51280513                1
[MBS2017] CMASS North 18716      15 21 36      +43 33.0       4        4 ...        282.4598 230.40200000  43.55000000                1
    2MASS J15215482+4336318 15 21 54.8183 +43 36 31.762      14       14 ...        285.6150 230.47840975  43.60882304                1
           UCAC4 669-059096 15 22 15.7626 +43 36 02.820      14       14 ...        289.4724 230.56567785  43.60078345                1

0.4.8+

from astroquery.simbad import Simbad

Simbad.add_votable_fields('distance_result')
ValueError: 'distance_result' is not one of the accepted options which can be listed with 'list_votable_fields'. Did you mean 'mesdistance'?

[keflavich]

I don't see any information on this field on SIMBAD's documentation, so @aoberto may want to give this some attention.

In the meantime, it's easy to add:

coords = SkyCoord(res['ra'], res['dec'], unit=(u.deg, u.deg))
res['DISTANCE_RESULT'] = coords.separation(s)

[havok2063]

That would work in the interim.

If a mapping were made and documented between the old and new fields, then this message
ValueError: 'distance_result' is not one of the accepted options which can be listed with 'list_votable_fields'. Did you mean 'mesdistance'?
could be improved with either something like "This field is no longer available", "This field has been deprecated and replaced with xxx" or "Please use the new field '[table_name.column_name]".

[bsipocz]

could be improved with either something like "This field is no longer available", "This field has been deprecated and replaced with xxx" or "Please use the new field '[table_name.column_name]".

I would not be against adding some info about it on the evolution docs page, but I feel this would add quite some complication to the code right now when this changes has been done and released a while ago.

cc @ManonMarchand

[ManonMarchand]

Hi all!

Yup, that's messy. This field is one of the only ones that only made sense for query_region whereas all the other ones were applied for all query methods.
Moreover, the current version of ADQL upstream does allow to return the distance if there is a single center but not for a list of centers. Thus, if we were to add a distance_result column to the output of query region, it would have to be calculated like in @keflavich 's suggestion. Would that help?

I can add a new exception there

astroquery/astroquery/simbad/utils.py

Line 17 in 9239e51

def _catch_deprecated_fields_with_arguments(votable_field):

to catch distance_result to make it more explicit that it is no longer a possible votable field.

To answer your other question:

Now that Simbad.list_votable_fields() returns a mix of tables and columns, is there a way to list all the available columns from all tables?

You can, it's:

from astroquery.simbad import Simbad
simbad = Simbad
simbad.list_columns()

But not all of them are available via a votable_field. The way it works is that votable_fields are shortcuts to avoid writing custom TAP queries. If your needs are beyond the classic use of astroquery, then you'll have to dig a bit into TAP. Don't hesitate to ask for help (issue here or email to the cds hotline) or to check the documentation about query_tap if you need a hint on how to redact your own query to access these columns.

[havok2063]

Hi, thanks all for your responses. It sounds like I just hit an edge-case. I would be OK with a documentation-only solution. Since the number of columns in the old 0.4.7 Simbad.list_votable_fields is small, I still think it would be good to add a table in the docs with the pre-0.4.8 votable_fields and its closest equivalent in the post 0.4.7 syntax of list_votable_fields.

If distance_result is the only problem-column, then maybe it doesn't require much code-change. Maybe add a section in the docs calling out this particular field with the new workaround? It's easy enough for users to add but it is a breaking change that is hard to be aware of it. I like your idea of adding it to the catch_deprecated_fields exception. In the exception message, you could point to the new docs section to highlight the workaround since it won't have a new column replacement.

I hadn't see the documentation at https://astroquery.readthedocs.io/en/latest/simbad/simbad.html#query-tap. This helps with understanding all the available columns.