Split migration into two parts

Unit tests remain to be split.

pycds/alembic/versions/8c05da87cb79_add_hx_tkg_to_obs_raw.py

@@ -1,4 +1,4 @@
-"""Add history tracking to obs_raw
+"""Add history tracking to obs_raw, part 1 (create hx table)
 
 Revision ID: 8c05da87cb79
 Revises: a59d64cf16ca
@@ -49,7 +49,6 @@ def upgrade():
 
     # Primary table
     ####
-
     add_history_cols_to_primary(
         table_name,
         columns=(
@@ -65,24 +64,14 @@ def upgrade():
 
     # History table
     ####
-
     create_history_table(table_name, foreign_keys)
-
-    # Populate the history table, then update its history FKs in bulk.
-    # If we let the FK trigger do this work, fired row-by-row on ~1e9 records,
-    # it requires an unfeasible amount of time, so we do it in bulk.
+    grant_standard_table_privileges(hx_table_name(table_name), schema=schema_name)
     populate_history_table(table_name, primary_key_name)
-    update_obs_raw_history_FKs()
-
-    # History table triggers must be created after the table is populated.
-    create_history_table_triggers(table_name, foreign_keys)
+    # History table hx foreign keys are updated in bulk in next migration.
 
-    create_history_table_indexes(table_name, primary_key_name, foreign_keys)
-    grant_standard_table_privileges(table_name, schema=schema_name)
 
 
 def downgrade():
-    drop_history_triggers(table_name)
     drop_history_table(table_name)
     drop_history_cols_from_primary(table_name, columns=("mod_user",))
     op.execute(

pycds/alembic/versions/976071a4f6e8_add_hx_tkg_to_obs_raw_part_2.py

@@ -0,0 +1,44 @@
+"""Add history tracking to obs_raw, part 2 (update FKs)
+
+Revision ID: 976071a4f6e8
+Revises: 8c05da87cb79
+Create Date: 2025-02-04 10:09:18.094153
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+from pycds import get_schema_name
+from pycds.alembic.change_history_utils import update_obs_raw_history_FKs, create_history_table_triggers, \
+    create_history_table_indexes, drop_history_triggers
+
+# revision identifiers, used by Alembic.
+revision = "976071a4f6e8"
+down_revision = "8c05da87cb79"
+branch_labels = None
+depends_on = None
+
+
+schema_name = get_schema_name()
+
+# TODO: These are the same as in the previous migration, but can't be accessed due
+#   to module naming. Use __import__()?
+table_name = "obs_raw"
+primary_key_name = "obs_raw_id"
+foreign_keys = [("meta_history", "history_id"), ("meta_vars", "vars_id")]
+
+
+def upgrade():
+    # If we let the FK trigger update FKs, fired row-by-row on ~1e9 records,
+    # it requires an unfeasible amount of time, so we do it in bulk.
+    update_obs_raw_history_FKs()
+    # History table triggers must be created after the table is populated.
+    create_history_table_triggers(table_name, foreign_keys)
+    create_history_table_indexes(table_name, primary_key_name, foreign_keys)
+
+
+def downgrade():
+    drop_history_triggers(table_name)
+    # We could set the hx FKs to NULL here, but there's not much point given this
+    # migration is paired with the previous one, whose downgrade immediately drops
+    # the entire table.