content: """Add log source [85289fea86ff].
  
  Revision ID: 85289fea86ff
  Revises: 5bb25e95849c
  Create Date: 2025-06-30 18:18:24.539265
  
  """
  
  import sqlalchemy as sa
  from alembic import op
  
  # revision identifiers, used by Alembic.
  revision = "85289fea86ff"
  down_revision = "5bb25e95849c"
  branch_labels = None
  depends_on = None
  
  
  def upgrade() -> None:
      """Upgrade database schema and/or data, creating a new revision."""
      # Add the source column as nullable first
      with op.batch_alter_table("logs", schema=None) as batch_op:
          batch_op.add_column(
              sa.Column("source", sa.VARCHAR(255), nullable=True)
          )
  
      # Populate the source field based on existing data
      connection = op.get_bind()
  
      # Set source to "step" where step_run_id is present
      connection.execute(
          sa.text("""
              UPDATE logs 
              SET source = 'step' 
              WHERE step_run_id IS NOT NULL
          """)
      )
  
      # Set source to "client" for all other cases (where step_run_id is null)
      connection.execute(
          sa.text("""
              UPDATE logs 
              SET source = 'client' 
              WHERE step_run_id IS NULL
          """)
      )
  
      # Make the source column not nullable
      with op.batch_alter_table("logs", schema=None) as batch_op:
          batch_op.alter_column(
              "source",
              existing_type=sa.VARCHAR(255),
              nullable=False,
          )
          # Add unique constraint: source is unique for each combination of pipeline_run_id and step_run_id
          batch_op.create_unique_constraint(
              "unique_source_per_run_and_step",
              ["source", "pipeline_run_id", "step_run_id"],
          )
  
  
  def downgrade() -> None:
      """Downgrade database schema and/or data back to the previous revision."""
      with op.batch_alter_table("logs", schema=None) as batch_op:
          batch_op.drop_constraint(
              "unique_source_per_run_and_step", type_="unique"
          )
          batch_op.drop_column("source")
  