-- Add version field for optimistic locking
-- This enables concurrent update detection to prevent lost updates

-- Add version column to mpc_sessions table
ALTER TABLE mpc_sessions
ADD COLUMN version BIGINT NOT NULL DEFAULT 1;

-- Add comment explaining the version field
COMMENT ON COLUMN mpc_sessions.version IS 'Version number for optimistic locking - increments on each update to detect concurrent modifications';

-- Create index on version for better query performance (optional but recommended)
CREATE INDEX idx_mpc_sessions_version ON mpc_sessions(id, version);