public void serializeMerge(QueryMetadata metadata, RelationalPath<?> entity,
            List<Path<?>> keys, List<Path<?>> columns, List<Expression<?>> values,
            SubQueryExpression<?> subQuery, SQLSerializer context) {
        context.serializeForMerge(metadata, entity, keys, columns, values, subQuery);

        if (!metadata.getFlags().isEmpty()) {
            context.serialize(Position.END, metadata.getFlags());
        }
    }
template method for MERGE serialization

@param metadata
@param entity
@param keys
@param columns
@param values
@param subQuery
@param context
querydsl-sql/src/main/java/com/querydsl/sql/SQLTemplates.java