Transition value JSON from old to new flat format

README_dev.md

@@ -0,0 +1,24 @@
+# Developing Data Transition
+
+## Testing `alembic` Migration
+
+1. Edit `./spinedb_api/alembic.ini`, point `sqlalchemy.url` to a (copy of a) SQLite test database. ⚠️ Its data will be altered by the migration script.
+1. Edit `./spinedb_api/alembic/versions/a973ab537da2_reencode_parameter_values.py` and temporarily change
+   ```python
+   new_value = transition_data(old_value)
+   ```
+   to
+   ```python
+   new_value = b'prepend_me ' + old_value
+   ```
+1. Within the `./spinedb_api` folder, execute
+   ```bash
+   alembic upgrade head
+   ```
+1. Open your SQLite test database in a database editor and check for changed `paramater_value`s.
+
+## Developing the Data Transition Module
+
+1. Edit `./spinedb_api/compat/reencode_for_data_transition.py` for development.
+1. In a Python REPL, call its function `transition_data(old_json_bytes)` and check for correct output of our test cases.
+1. Once this works, revert the changes of `./spinedb_api/alembic/versions/a973ab537da2_reencode_parameter_values.py` and test the above `alembic` migration again.

spinedb_api/alembic/versions/8b0eff478bcb_add_active_by_default_to_entity_class.py

@@ -9,7 +9,7 @@
 from alembic import op
 import sqlalchemy as sa
 import sqlalchemy.orm
-from spinedb_api.compatibility import convert_tool_feature_method_to_active_by_default
+from spinedb_api.compat.compatibility_transformations import convert_tool_feature_method_to_active_by_default
 
 # revision identifiers, used by Alembic.
 revision = "8b0eff478bcb"

spinedb_api/alembic/versions/a973ab537da2_reencode_parameter_values.py

@@ -0,0 +1,60 @@
+"""reencode parameter_values
+
+Revision ID: a973ab537da2
+Revises: 91f1f55aa972
+Create Date: 2025-05-21 12:49:16.861670
+
+"""
+
+from alembic import op
+import sqlalchemy as sa
+from spinedb_api.compat.reencode_for_data_transition import transition_data
+
+
+# revision identifiers, used by Alembic.
+revision = "a973ab537da2"
+down_revision = "91f1f55aa972"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # Reflect table definition
+    conn = op.get_bind()
+    metadata = sa.MetaData()
+    metadata.bind = conn
+
+    # Define a lightweight representation of the table
+    my_table = sa.Table(
+        "parameter_value",
+        metadata,
+        sa.Column("id", sa.Integer, primary_key=True),
+        sa.Column("value", sa.BINARY),
+        sa.Column("type", sa.String),  # TODO do we need the type?
+    )
+
+    # Read current data
+    results = conn.execute(sa.select(my_table.c.id, my_table.c.value, my_table.c.type)).fetchall()
+
+    # NOTE: maybe this should be derived from `models.ValueTypeNames`,
+    # but we don't want non-JSON values like integer, number, boolean;
+    # also some names differ by `-` <-> `_`
+    convertible = ("date_time", "duration", "time_pattern", "time_series", "array", "map")
+
+    # Apply transformation
+    for row in results:
+        if row.type not in convertible:
+            continue
+        old_value = row.value
+        new_value = transition_data(old_value)
+
+        # FIXME:
+        # - `type` also needs translation; from the `convertible`
+        #   list, ("time_series", "array", "map") -> "table"
+        # - can the insertions be queued?
+        # Update the row
+        conn.execute(my_table.update().where(my_table.c.id == row.id).values(value=new_value))
+
+
+def downgrade():
+    pass

spinedb_api/alembic/versions/ce9faa82ed59_create_entity_alternative_table.py

@@ -8,7 +8,7 @@
 
 from alembic import op
 import sqlalchemy as sa
-from spinedb_api.compatibility import convert_tool_feature_method_to_entity_alternative
+from spinedb_api.compat.compatibility_transformations import convert_tool_feature_method_to_entity_alternative
 
 # revision identifiers, used by Alembic.
 revision = "ce9faa82ed59"