Rework visit-visit_system relationship.

A visit can now belong to multiple visit_systems, as long as the set
of exposures computed by those visit_systems is the same.

python/lsst/daf/butler/configs/dimensions.yaml

@@ -163,7 +163,7 @@ elements:
         type: string
         length: 64
     requires: [instrument]
-    implies: [physical_filter, visit_system]
+    implies: [physical_filter]
     metadata:
       -
         name: day_obs
@@ -217,6 +217,14 @@ elements:
           Can only be approximate since it is continuously changing during
           an observation and multiple exposures can be combined from a
           relatively long period.
+
+      -
+        name: visit_system_mask
+        type: int
+        doc: >
+          A bitwise OR of ``2**(visit_system.id)`` for the visit systems this
+          visit belongs to, provided to allow queries to sometimes avoid
+          joining in ``visit_system`` and ``visit_system_membership``.
     storage:
       cls: lsst.daf.butler.registry.dimensions.table.TableDimensionRecordStorage
 
@@ -435,6 +443,12 @@ elements:
     doc: >
       A system of self-consistent visit definitions, within which each
       exposure should appear at most once.
+
+      A visit may belong to multiple visit systems, if the logical definitions
+      for those systems happen to result in the same set of exposures - the
+      main (and probably only) example is when a single-snap visit is observed,
+      for which both the "one-to-one" visit system and a "group by header metadata" visit
+      system will define the same single-exposure visit.
     keys:
       -
         name: id
@@ -453,8 +467,16 @@ elements:
     doc: >
       A many-to-many join table that relates exposures to the visits they
       belong to.
-    requires: [exposure, visit_system]
-    implies: [visit]
+    requires: [exposure, visit]
+    always_join: true
+    storage:
+      cls: lsst.daf.butler.registry.dimensions.table.TableDimensionRecordStorage
+
+  visit_system_membership:
+    doc: >
+      A many-to-many join table that relates visits to the visit_systems they
+      belong to.
+    requires: [visit, visit_system]
     always_join: true
     storage:
       cls: lsst.daf.butler.registry.dimensions.table.TableDimensionRecordStorage

python/lsst/daf/butler/tests/utils.py

@@ -239,7 +239,7 @@ def __init__(self, root, configFile):
                 id=423,
                 name="fourtwentythree",
                 physical_filter="d-r",
-                visit_system=1,
+                visit_system_mask=2,  # 2**1
                 datetimeBegin=visitStart,
                 datetimeEnd=visitEnd,
             ),
@@ -251,7 +251,7 @@ def __init__(self, root, configFile):
                 id=424,
                 name="fourtwentyfour",
                 physical_filter="d-r",
-                visit_system=1,
+                visit_system_mask=2,
             ),
         )
 

tests/test_cliCmdQueryDataIds.py

@@ -65,8 +65,8 @@ def testDimensions(self):
         """Test getting a dimension."""
         res = self._queryDataIds(self.root, dimensions=("visit",))
         expected = AstropyTable(
-            array((("R", "DummyCamComp", "d-r", 1, 423), ("R", "DummyCamComp", "d-r", 1, 424))),
-            names=("band", "instrument", "physical_filter", "visit_system", "visit"),
+            array((("R", "DummyCamComp", "d-r", 423), ("R", "DummyCamComp", "d-r", 424))),
+            names=("band", "instrument", "physical_filter", "visit"),
         )
         self.assertAstropyTablesEqual(res, expected)
 
@@ -81,8 +81,8 @@ def testWhere(self):
             self.root, dimensions=("visit",), where="instrument='DummyCamComp' AND visit=423"
         )
         expected = AstropyTable(
-            array((("R", "DummyCamComp", "d-r", 1, 423),)),
-            names=("band", "instrument", "physical_filter", "visit_system", "visit"),
+            array((("R", "DummyCamComp", "d-r", 423),)),
+            names=("band", "instrument", "physical_filter", "visit"),
         )
         self.assertAstropyTablesEqual(res, expected)
 
@@ -98,7 +98,6 @@ def testDatasetsAndCollections(self):
                 "id": 425,
                 "name": "fourtwentyfive",
                 "physical_filter": "d-r",
-                "visit_system": 1,
             },
         )
         self.repo.addDataset(dataId={"instrument": "DummyCamComp", "visit": 425}, run="foo")
@@ -108,8 +107,8 @@ def testDatasetsAndCollections(self):
             repo=self.root, dimensions=("visit",), collections=("ingest/run",), datasets="test_metric_comp"
         )
         expected = AstropyTable(
-            array((("R", "DummyCamComp", "d-r", 1, 423), ("R", "DummyCamComp", "d-r", 1, 424))),
-            names=("band", "instrument", "physical_filter", "visit_system", "visit"),
+            array((("R", "DummyCamComp", "d-r", 423), ("R", "DummyCamComp", "d-r", 424))),
+            names=("band", "instrument", "physical_filter", "visit"),
         )
         self.assertAstropyTablesEqual(res, expected)
 
@@ -118,8 +117,8 @@ def testDatasetsAndCollections(self):
             repo=self.root, dimensions=("visit",), collections=("foo",), datasets="test_metric_comp"
         )
         expected = AstropyTable(
-            array((("R", "DummyCamComp", "d-r", 1, 425),)),
-            names=("band", "instrument", "physical_filter", "visit_system", "visit"),
+            array((("R", "DummyCamComp", "d-r", 425),)),
+            names=("band", "instrument", "physical_filter", "visit"),
         )
         self.assertAstropyTablesEqual(res, expected)
 

tests/test_cliCmdQueryDatasetTypes.py

@@ -128,7 +128,7 @@ def testQueryDatasetTypes(self):
                 array(
                     (
                         "test",
-                        "['band', 'instrument', 'physical_filter', 'visit_system', 'visit']",
+                        "['band', 'instrument', 'physical_filter', 'visit']",
                         storageClassName,
                     )
                 ),