# Create input joins from list of input tables

    in_tables_ = in_tables[:] # don't modify input!

    in_tables0 = in_tables_.pop(0) # first table is separate

    in_pkey = pkey(db, in_tables0, recover=True)

    in_pkey_col = sql_gen.as_Col(in_pkey, in_tables0)

    input_joins = [in_tables0]+[sql_gen.Join(v,

        log_debug('Caught exception: '+e_str)

        assert e_str not in exc_strs # avoid infinite loops

        exc_strs.add(e_str)

    def remove_all_rows():

        log_debug('Returning NULL for all rows')

        limit_ref[0] = 0 # just create an empty pkeys table

    def ignore(in_col, value):

        in_col_str = strings.as_tt(repr(in_col))

        db.log_debug('Adding index on '+in_col_str+' to enable fast filtering',

            level=2.5)

        add_index(db, in_col)

        log_debug('Ignoring rows with '+in_col_str+' = '

            +strings.as_tt(repr(value)))

    def remove_rows(in_col, value):

            log_debug('Casting '+strings.as_tt(out_col)+' input to '

                +strings.as_tt(type_))

            mapping[out_col] = sql_gen.wrap(wrap_func, mapping[out_col])

        except DatabaseErrors, e:

            log_exc(e)