fix: add h3 to alpn enum in db

app/db/migrations/versions/305943d779c4_add_h3_to_alpn_enum.py

@@ -0,0 +1,118 @@
+"""add h3 to alpn enum
+
+Revision ID: 305943d779c4
+Revises: 31f92220c0d0
+Create Date: 2024-07-03 19:27:15.282711
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '305943d779c4'
+down_revision = '31f92220c0d0'
+branch_labels = None
+depends_on = None
+
+
+# Describing of enum
+enum_name = "alpn"
+temp_enum_name = f"temp_{enum_name}"
+old_values = ("", "h2", "http/1.1", "h2,http/1.1")
+new_values = ("h3", "h3,h2", "h3,h2,http/1.1", *old_values)
+# on downgrade convert [0] to [1]
+downgrade_from = ("h3", "h3,h2", "h3,h2,http/1.1")
+downgrade_to = ("")
+old_type = sa.Enum(*old_values, name=enum_name)
+new_type = sa.Enum(*new_values, name=enum_name)
+temp_type = sa.Enum(*new_values, name=temp_enum_name)
+
+
+# Describing of table
+table_name = "hosts"
+column_name = "alpn"
+temp_table = sa.sql.table(
+    table_name,
+    sa.Column(
+        column_name,
+        new_type,
+        nullable=False
+    )
+)
+
+
+def upgrade():
+    # temp type to use instead of old one
+    temp_type.create(op.get_bind(), checkfirst=False)
+
+    # changing of column type from old enum to new one.
+    # SQLite will create temp table for this
+    with op.batch_alter_table(table_name) as batch_op:
+        batch_op.alter_column(
+            column_name,
+            existing_type=old_type,
+            type_=temp_type,
+            existing_nullable=False,
+            postgresql_using=f"{column_name}::text::{temp_enum_name}"
+        )
+
+    # remove old enum, create new enum
+    old_type.drop(op.get_bind(), checkfirst=False)
+    new_type.create(op.get_bind(), checkfirst=False)
+
+    # changing of column type from temp enum to new one.
+    # SQLite will create temp table for this
+    with op.batch_alter_table(table_name) as batch_op:
+        batch_op.alter_column(
+            column_name,
+            existing_type=temp_type,
+            type_=new_type,
+            existing_nullable=False,
+            postgresql_using=f"{column_name}::text::{enum_name}"
+        )
+
+    # remove temp enum
+    temp_type.drop(op.get_bind(), checkfirst=False)
+
+
+def downgrade():
+    # old enum don't have new value anymore.
+    # before downgrading from new enum to old one,
+    # we should replace new value from new enum with
+    # somewhat of old values from old enum
+    op.execute(
+        temp_table
+        .update()
+        .where(
+            temp_table.c.status in downgrade_from
+        )
+        .values(
+            status=downgrade_to
+        )
+    )
+
+    temp_type.create(op.get_bind(), checkfirst=False)
+
+    with op.batch_alter_table(table_name) as batch_op:
+        batch_op.alter_column(
+            column_name,
+            existing_type=new_type,
+            type_=temp_type,
+            existing_nullable=False,
+            postgresql_using=f"{column_name}::text::{temp_enum_name}"
+        )
+
+    new_type.drop(op.get_bind(), checkfirst=False)
+    old_type.create(op.get_bind(), checkfirst=False)
+
+    with op.batch_alter_table(table_name) as batch_op:
+        batch_op.alter_column(
+            column_name,
+            existing_type=temp_type,
+            type_=old_type,
+            existing_nullable=False,
+            postgresql_using=f"{column_name}::text::{enum_name}"
+        )
+
+    temp_type.drop(op.get_bind(), checkfirst=False)