compare.py 文件源码

def _compare_type(
    autogen_context, alter_column_op, schema, tname, cname, conn_col,
        metadata_col):

    conn_type = conn_col.type
    alter_column_op.existing_type = conn_type
    metadata_type = metadata_col.type
    if conn_type._type_affinity is sqltypes.NullType:
        log.info("Couldn't determine database type "
                 "for column '%s.%s'", tname, cname)
        return
    if metadata_type._type_affinity is sqltypes.NullType:
        log.info("Column '%s.%s' has no type within "
                 "the model; can't compare", tname, cname)
        return

    isdiff = autogen_context.migration_context._compare_type(
        conn_col, metadata_col)

    if isdiff:
        alter_column_op.modify_type = metadata_type
        log.info("Detected type change from %r to %r on '%s.%s'",
                 conn_type, metadata_type, tname, cname
                 )