Fix _merge_repr for numeric data types (#786)

src/spyglass/utils/dj_merge_tables.py

@@ -245,33 +245,32 @@ def _merge_repr(cls, restriction: str = True) -> dj.expression.Union:
             for p in cls._merge_restrict_parts(
                 restriction=restriction,
                 add_invalid_restrict=False,
-                return_empties=True,
+                return_empties=False,  # motivated by SpikeSortingOutput.Import
             )
         ]
 
-        primary_attrs = list(
-            dict.fromkeys(  # get all columns from parts
-                iter_chain.from_iterable([p.heading.names for p in parts])
+        attr_dict = {  # NULL for non-numeric, 0 for numeric
+            attr.name: "0" if attr.numeric else "NULL"
+            for attr in iter_chain.from_iterable(
+                part.heading.attributes.values() for part in parts
             )
-        )
-        # primary_attrs.append(cls()._reserved_sk)
-        query = dj.U(*primary_attrs) * parts[0].proj(  # declare query
-            ...,  # include all attributes from part 0
-            **{
-                a: "NULL"  # add null value where part has no column
-                for a in primary_attrs
-                if a not in parts[0].heading.names
-            },
-        )
-        for part in parts[1:]:  # add to declared query for each part
-            query += dj.U(*primary_attrs) * part.proj(
-                ...,
+        }
+
+        def _proj_part(part):
+            """Project part, adding NULL/0 for missing attributes"""
+            return dj.U(*attr_dict.keys()) * part.proj(
+                ...,  # include all attributes from part
                 **{
-                    a: "NULL"
-                    for a in primary_attrs
-                    if a not in part.heading.names
+                    k: v
+                    for k, v in attr_dict.items()
+                    if k not in part.heading.names
                 },
             )
+
+        query = _proj_part(parts[0])  # start with first part
+        for part in parts[1:]:  # add remaining parts
+            query += _proj_part(part)
+
         return query
 
     @classmethod
@@ -529,6 +528,12 @@ def fetch_nwb(
         multi_source: bool
             Return from multiple parents. Default False.
         """
+        if isinstance(self, dict):
+            raise ValueError("Try replacing Merge.method with Merge().method")
+        if restriction == True and self.restriction:
+            if not disable_warning:
+                _warn_on_restriction(self, restriction)
+            restriction = self.restriction
 
         return self.merge_restrict_class(restriction).fetch_nwb()