public Statistics createUnknownStatistics(
            Table table,
            List<ColumnRefOperator> columns,
            List<PartitionKey> partitionKeys,
            double presentRowNums) {
        Statistics.Builder builder = Statistics.builder();
        for (ColumnRefOperator columnRefOperator : columns) {
            builder.addColumnStatistic(columnRefOperator, ColumnStatistic.unknown());
        }

        double totalRowNums = 0;
        try {
            totalRowNums = presentRowNums >= 0 ? presentRowNums : getEstimatedRowCount(table, partitionKeys);
        } catch (Exception e) {
            LOG.warn("Failed to estimate row count on table [{}]", table);
        } finally {
            builder.setOutputRowCount(totalRowNums);
        }

        return builder.build();
    }
@Test
    public void testCreateUnknownStatistics() throws AnalysisException {
        HiveTable hiveTable = (HiveTable) hmsOps.getTable("db1", "table1");
        ColumnRefOperator partColumnRefOperator = new ColumnRefOperator(0, Type.INT, "col1", true);
        ColumnRefOperator dataColumnRefOperator = new ColumnRefOperator(1, Type.INT, "col2", true);
        PartitionKey hivePartitionKey1 = PartitionUtil.createPartitionKey(
                Lists.newArrayList("1"), hiveTable.getPartitionColumns());
        PartitionKey hivePartitionKey2 = PartitionUtil.createPartitionKey(
                Lists.newArrayList("2"), hiveTable.getPartitionColumns());

        Statistics statistics = statisticsProvider.createUnknownStatistics(
                hiveTable, Lists.newArrayList(partColumnRefOperator, dataColumnRefOperator),
                Lists.newArrayList(hivePartitionKey1, hivePartitionKey2), 100);
        Assert.assertEquals(100, statistics.getOutputRowCount(), 0.001);
        Assert.assertEquals(2, statistics.getColumnStatistics().size());
        Assert.assertTrue(statistics.getColumnStatistics().get(partColumnRefOperator).isUnknown());
        Assert.assertTrue(statistics.getColumnStatistics().get(dataColumnRefOperator).isUnknown());
    }