presto-main/src/main/java/io/prestosql/operator/TableDeleteOperator.java/TableDeleteOperator/getOutput
class TableDeleteOperator:    @Override
    public Page getOutput()
    {
        if (finished) {
            return null;
        }
        finished = true;

        OptionalLong rowsDeletedCount = metadata.executeDelete(session, tableHandle);

        // output page will only be constructed once,
        // so a new PageBuilder is constructed (instead of using PageBuilder.reset)
        PageBuilder page = new PageBuilder(1, TYPES);
        BlockBuilder rowsBuilder = page.getBlockBuilder(0);
        page.declarePosition();
        if (rowsDeletedCount.isPresent()) {
            BIGINT.writeLong(rowsBuilder, rowsDeletedCount.getAsLong());
        }
        else {
            rowsBuilder.appendNull();
        }
        return page.build();
    }