Make extra table constraints subqueried

CHANGES.rst

@@ -26,6 +26,9 @@ Enhancements and Fixes
   any model serialized in VO-DML. This package dynamically generates python objects
   whose structure corresponds to the classes of the mapped models. [#497]
 
+- RegTAP constraints involving tables other than rr.resource are now
+  done via subqueries for less duplication of interfaces. [#562]
+
 
 Deprecations and Removals
 -------------------------

pyvo/registry/regtap.py

@@ -784,7 +784,6 @@ def get_interface(self, *,
                           if ((not std_only) or intf.is_standard)
                           and not intf.is_vosi
                           and ((not service_type) or intf.supports(service_type))]
-
         if not candidates:
             raise ValueError("No matching interface.")
 

pyvo/registry/rtcons.py

@@ -162,6 +162,10 @@ class Constraint:
     sequences of constraints.  Constraints that want to the all
     arguments in the constructor can set takes_sequence to True.
     """
+    # TODO: _extra_tables is only used in the legacy leg of
+    # the fulltext constraint any more, and there it's wrong, too.
+    # Let's do away with extra_tables and tell people to use
+    # SubqueriedConstraint whenever they think they need it.
     _extra_tables = []
     _condition = None
     _fillers = None
@@ -205,6 +209,36 @@ def _get_sql_literals(self):
         return {}
 
 
+class SubqueriedConstraint(Constraint):
+    """
+    An (abstract) constraint for when the constraint is over a table
+    other than rr.resource.
+
+    We need to be careful with these, because they will in general have
+    1:n relationships to rr.resource, and these will lead to
+    duplicated interfaces if we just do the NATURAL JOIN we normally
+    do.
+
+    Instead, we have to resort to ivoid in (subquery) conditions.  In
+    particular, extra_tables will always be empty for these.
+
+    To configure those, give the table to query in _subquery_table
+    and _condition, _fillers, and _keyword as usual.  The rest is taken
+    care of by get_search_condition.
+    """
+    _subquery_table = None
+
+    def get_search_condition(self, service):
+        if self._condition is None or self._subquery_table is None:
+            raise NotImplementedError("{} is an abstract Constraint"
+                                      .format(self.__class__.__name__))
+
+        return ("ivoid IN (SELECT ivoid FROM {subquery_table}"
+            " WHERE {condition})".format(
+                subquery_table=self._subquery_table,
+                condition=self._condition.format(**self._get_sql_literals())))
+
+
 class Freetext(Constraint):
     """
     A contraint using plain text to match against title, description,
@@ -284,14 +318,15 @@ def _get_or_condition(self, service):
         return super().get_search_condition(service)
 
 
-class Author(Constraint):
+class Author(SubqueriedConstraint):
     """
     A constraint for creators (“authors”) of a resource; you can use SQL
     patterns here.
 
     The match is case-sensitive.
     """
     _keyword = "author"
+    _subquery_table = "rr.res_role"
 
     def __init__(self, name: str):
         """
@@ -306,7 +341,6 @@ def __init__(self, name: str):
         """
         self._condition = "role_name LIKE {auth} AND base_role='creator'"
         self._fillers = {"auth": name}
-        self._extra_tables = ["rr.res_role"]
 
 
 class Servicetype(Constraint):
@@ -451,7 +485,7 @@ def __init__(self, *bands):
             for band in self.bands)
 
 
-class Datamodel(Constraint):
+class Datamodel(SubqueriedConstraint):
     """
     A constraint on the adherence to a data model.
 
@@ -486,30 +520,30 @@ def __init__(self, dmname):
         if dmname not in self._known_dms:
             raise dalq.DALQueryError("Unknown data model id {}.  Known are: {}."
                                      .format(dmname, ", ".join(sorted(self._known_dms))))
-        self._condition = getattr(self, f"_make_{dmname}_constraint")()
+        self._subquery_table, self._condition = getattr(
+            self, f"_make_{dmname}_constraint")()
 
     def _make_obscore_constraint(self):
         # There was a bit of chaos with the DM ids for Obscore.
         # Be lenient here
-        self._extra_tables = ["rr.res_detail"]
         obscore_pat = 'ivo://ivoa.net/std/obscore%'
-        return ("detail_xpath = '/capability/dataModel/@ivo-id'"
-                f" AND 1 = ivo_nocasematch(detail_value, '{obscore_pat}')")
+        return "rr.res_detail", (
+            "detail_xpath = '/capability/dataModel/@ivo-id'"
+            f" AND 1 = ivo_nocasematch(detail_value, '{obscore_pat}')")
 
     def _make_epntap_constraint(self):
-        self._extra_tables = ["rr.res_table"]
         # we include legacy, pre-IVOA utypes for matches; lowercase
         # any new identifiers (utypes case-fold).
-        return " OR ".join(
+        return "rr.res_table", " OR ".join(
             f"table_utype LIKE '{pat}'" for pat in
             ['ivo://vopdc.obspm/std/epncore#schema-2.%',
              'ivo://ivoa.net/std/epntap#table-2.%'])
 
     def _make_regtap_constraint(self):
-        self._extra_tables = ["rr.res_detail"]
         regtap_pat = 'ivo://ivoa.net/std/RegTAP#1.%'
-        return ("detail_xpath = '/capability/dataModel/@ivo-id'"
-                f" AND 1 = ivo_nocasematch(detail_value, '{regtap_pat}')")
+        return "rr.res_detail", (
+            "detail_xpath = '/capability/dataModel/@ivo-id'"
+            f" AND 1 = ivo_nocasematch(detail_value, '{regtap_pat}')")
 
 
 class Ivoid(Constraint):
@@ -540,12 +574,13 @@ def get_search_condition(self, service):
             f"ivoid={make_sql_literal(id)}" for id in self.ivoids)
 
 
-class UCD(Constraint):
+class UCD(SubqueriedConstraint):
     """
     A constraint selecting resources having tables with columns having
     UCDs matching a SQL pattern (% as wildcard).
     """
     _keyword = "ucd"
+    _subquery_table = "rr.table_column"
 
     def __init__(self, *patterns):
         """
@@ -558,14 +593,13 @@ def __init__(self, *patterns):
             UCDs.  The constraint will match when a resource has
             at least one column matching one of the patterns.
         """
-        self._extra_tables = ["rr.table_column"]
         self._condition = " OR ".join(
             f"ucd LIKE {{ucd{i}}}" for i in range(len(patterns)))
         self._fillers = dict((f"ucd{index}", pattern)
                              for index, pattern in enumerate(patterns))
 
 
-class Spatial(Constraint):
+class Spatial(SubqueriedConstraint):
     """
     A RegTAP constraint selecting resources covering a geometry in
     space.
@@ -614,7 +648,7 @@ class Spatial(Constraint):
         >>> resources = registry.Spatial((SkyCoord("23d +3d"), 3))
     """
     _keyword = "spatial"
-    _extra_tables = ["rr.stc_spatial"]
+    _subquery_table = "rr.stc_spatial"
 
     takes_sequence = True
 
@@ -702,7 +736,7 @@ def get_search_condition(self, service):
         return super().get_search_condition(service)
 
 
-class Spectral(Constraint):
+class Spectral(SubqueriedConstraint):
     """
     A RegTAP constraint on the spectral coverage of resources.
 
@@ -735,7 +769,7 @@ class Spectral(Constraint):
         >>> resources =  registry.Spectral((88*u.MHz, 102*u.MHz))
     """
     _keyword = "spectral"
-    _extra_tables = ["rr.stc_spectral"]
+    _subquery_table = "rr.stc_spectral"
 
     takes_sequence = True
 
@@ -798,7 +832,7 @@ def get_search_condition(self, service):
         return super().get_search_condition(service)
 
 
-class Temporal(Constraint):
+class Temporal(SubqueriedConstraint):
     """
     A RegTAP constraint on the temporal coverage of resources.
 
@@ -827,7 +861,7 @@ class Temporal(Constraint):
         >>> resources = registry.Temporal((54130, 54200))
     """
     _keyword = "temporal"
-    _extra_tables = ["rr.stc_temporal"]
+    _subquery_table = "rr.stc_temporal"
 
     takes_sequence = True
 

pyvo/registry/tests/test_regtap.py

@@ -146,7 +146,7 @@ def datamodeltest_callback(request, content):
         query = data['QUERY']
 
         assert (
-            "(detail_xpath = '/capability/dataModel/@ivo-id'" in query)
+            "detail_xpath = '/capability/dataModel/@ivo-id'" in query)
 
         assert (
             "ivo_nocasematch(detail_value, 'ivo://ivoa.net/std/obscore%'))"
@@ -349,13 +349,15 @@ def get_regtap_results(**kwargs):
 def test_spatial():
     assert (rtcons.keywords_to_constraints({
             "spatial": (23, -40)})[0].get_search_condition(FAKE_GAVO)
-            == "1 = CONTAINS(MOC(6, POINT(23, -40)), coverage)")
+            == "ivoid IN (SELECT ivoid FROM rr.stc_spatial"
+            " WHERE 1 = CONTAINS(MOC(6, POINT(23, -40)), coverage))")
 
 
 def test_spectral():
     assert (rtcons.keywords_to_constraints({
             "spectral": (1e-17, 2e-17)})[0].get_search_condition(FAKE_GAVO)
-            == "1 = ivo_interval_overlaps(spectral_start, spectral_end, 1e-17, 2e-17)")
+            == "ivoid IN (SELECT ivoid FROM rr.stc_spectral WHERE"
+            " 1 = ivo_interval_overlaps(spectral_start, spectral_end, 1e-17, 2e-17))")
 
 
 def test_to_table(multi_interface_fixture, capabilities):