Add schema.lineage property to view all lineages

- Add get_schema_lineages() function in lineage.py
- Add schema.lineage property returning flat dict mapping
  'schema.table.attribute' to its lineage origin
- Add note about A - B without semantic check in spec
- Document schema.lineage in API reference

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: dimitri-yatsenko

docs/src/design/semantic-matching-spec.md

@@ -128,6 +128,19 @@ if schema.lineage_table_exists:
 
 **Returns**: `bool` - `True` if `~lineage` table exists, `False` otherwise.
 
+#### `schema.lineage`
+
+Property returning all lineage entries for the schema.
+
+```python
+schema.lineage
+# {'myschema.session.session_id': 'myschema.session.session_id',
+#  'myschema.trial.session_id': 'myschema.session.session_id',
+#  'myschema.trial.trial_num': 'myschema.trial.trial_num'}
+```
+
+**Returns**: `dict` - Maps `'schema.table.attribute'` to its lineage origin
+
 ### Join Methods
 
 #### `expr.join(other, semantic_check=True)`
@@ -174,6 +187,8 @@ Equivalent to `A.restrict(B, semantic_check=True)`.
 
 Restriction with negation. Semantic checking applies.
 
+To bypass semantic checking: `A.restrict(dj.Not(B), semantic_check=False)`
+
 #### `A + B` (Union)
 
 Union of expressions. Requires all namesake attributes to have matching lineage.

src/datajoint/lineage.py

@@ -109,6 +109,26 @@ def get_table_lineages(connection, database, table_name):
     return {row[0]: row[1] for row in results}
 
 
+def get_schema_lineages(connection, database):
+    """
+    Get all lineages for a schema from the ~lineage table.
+
+    :param connection: A DataJoint connection object
+    :param database: The schema/database name
+    :return: A dict mapping 'schema.table.attribute' to its lineage
+    """
+    if not lineage_table_exists(connection, database):
+        return {}
+
+    results = connection.query(
+        """
+        SELECT table_name, attribute_name, lineage FROM `{database}`.`~lineage`
+        """.format(database=database),
+    ).fetchall()
+
+    return {f"{database}.{table}.{attr}": lineage for table, attr, lineage in results}
+
+
 def insert_lineages(connection, database, entries):
     """
     Insert multiple lineage entries in the ~lineage table as a single transaction.

src/datajoint/schemas.py

@@ -333,6 +333,18 @@ def lineage_table_exists(self):
         self._assert_exists()
         return lineage_table_exists(self.connection, self.database)
 
+    @property
+    def lineage(self):
+        """
+        Get all lineages for tables in this schema.
+
+        :return: A dict mapping 'schema.table.attribute' to its lineage
+        """
+        from .lineage import get_schema_lineages
+
+        self._assert_exists()
+        return get_schema_lineages(self.connection, self.database)
+
     def rebuild_lineage(self):
         """
         Rebuild the ~lineage table for all tables in this schema.