exec/java-exec/src/test/java/org/apache/drill/exec/store/easy/json/loader/TestScalars.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.drill.exec.store.easy.json.loader;

import static org.apache.drill.test.rowSet.RowSetUtilities.dec;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.time.LocalDateTime;

import org.apache.drill.categories.JsonTest;
import org.apache.drill.common.exceptions.UserException;
import org.apache.drill.common.types.TypeProtos.MinorType;
import org.apache.drill.exec.physical.rowSet.RowSet;
import org.apache.drill.exec.record.metadata.SchemaBuilder;
import org.apache.drill.exec.record.metadata.TupleMetadata;
import org.apache.drill.test.rowSet.RowSetUtilities;
import org.junit.Test;
import org.junit.experimental.categories.Category;

/**
 * Tests JSON scalar handling. Without a schema, the first non-null value
 * determines the type of the column. With a schema, then the schema determines
 * the column type independent of the first data row.
 * <p>
 * In either case, all scalars perform conversion from all other scalars. If data
 * is clean, then the conversion will never be used. If the data is messy, then
 * the result, when combined with a schema, produces a repeatable (if perhaps still
 * messy) result. The goal is that, with a schema, the query should not fail due
 * to a few messy rows a billion rows in, or due to the order that the scanners
 * see the data.
 */
@Category(JsonTest.class)
public class TestScalars extends BaseJsonLoaderTest {

  /**
   * Test Boolean type using type inference to guess the type from the
   * first row of data. All other types can be converted to Boolean.
   */
  @Test
  public void testBoolean() {
    String json =
        "{a: true} {a: false} {a: null} " +
        "{a: 1} {a: 0} " +
        "{a: 1.0} {a: 0.0} " +
        "{a: \"true\"} {a: \"\"} {a: \"false\"} {a: \"other\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.BIT)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow(true)   // true
        .addRow(false)  // false
        .addRow((Boolean) null)   // null
        .addRow(true)   // 1
        .addRow(false)  // 0
        .addRow(true)   // 1.0
        .addRow(false)  // 0.0
        .addRow(true)   // "true"
        .addRow((Boolean) null)  // ""
        .addRow(false)  // "false"
        .addRow(false)  // "other"
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testAllTextBoolean() {
    String json =
        "{a: true} {a: false} {a: null}";

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allTextMode = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow("true")   // true
        .addRow("false")  // false
        .addRow((String) null)    // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  /**
   * Test Boolean with a provided schema which states the column type
   * independent of the first value. Test with leading values which are
   * not Boolean.
   */
  @Test
  public void testBooleanWithSchema() {
    String json =
        "{a: 1} {a: 0} " +
        "{a: 1.0} {a: 0.0} " +
        "{a: \"true\"} {a: \"\"} {a: \"false\"} {a: \"other\"}" +
        "{a: true} {a: false} {a: null}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("a", MinorType.BIT)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow(true)   // 1
        .addRow(false)  // 0
        .addRow(true)   // 1.0
        .addRow(false)  // 0.0
        .addRow(true)   // "true"
        .addRow((Boolean) null)  // ""
        .addRow(false)  // "false"
        .addRow(false)  // "other"
        .addRow(true)   // true
        .addRow(false)  // false
        .addRow((Boolean) null)   // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testInt() {
    String json =
        "{a: 1} {a: 0} {a: -300} {a: null} " +
        "{a: true} {a: false} " +
        "{a: 1.0} {a: 1.4} {a: 1.5} {a: 0.0} " +
        "{a: \"\"} {a: \"3\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.BIGINT)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow(1)      // 1
        .addRow(0)      // 0
        .addRow(-300)   // -300
        .addRow((Long) null)   // null
        .addRow(1)      // true
        .addRow(0)      // false
        .addRow(1)      // 1.0
        .addRow(1)      // 1.4
        .addRow(2)      // 1.5
        .addRow(0)      // 0.0
        .addRow((Long) null)   // ""
        .addRow(3)      // "3"
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testIntAsDouble() {
    String json =
        "{a: 1} {a: 0} {a: -300} {a: null} " +
        "{a: true} {a: false} " +
        "{a: 1.0} {a: 1.5} {a: 0.0} " +
        "{a: \"\"} {a: \"3\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.readNumbersAsDouble = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.FLOAT8)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow(1D)      // 1
        .addRow(0D)      // 0
        .addRow(-300D)   // -300
        .addRow((Double) null)   // null
        .addRow(1D)      // true
        .addRow(0D)      // false
        .addRow(1D)      // 1.0
        .addRow(1.5D)    // 1.5
        .addRow(0D)      // 0.0
        .addRow((Double) null)   // ""
        .addRow(3D)      // "3"
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testAllTextInt() {
    String json =
        "{a: 1} {a: 0} {a: -300} {a: null}";

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allTextMode = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow("1")    // 1
        .addRow("0")    // 0
        .addRow("-300") // -300
        .addRow((String) null)    // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testIntWithSchema() {
    String json =
        "{a: true} {a: false} " +
        "{a: 1.0} {a: 1.4} {a: 1.5} {a: 0.0} " +
        "{a: \"\"} {a: \"3\"} " +
        "{a: 1} {a: 0} {a: -300} {a: null}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("a", MinorType.BIGINT)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow(1)      // true
        .addRow(0)      // false
        .addRow(1)      // 1.0
        .addRow(1)      // 1.4
        .addRow(2)      // 1.5
        .addRow(0)      // 0.0
        .addRow((Long) null)   // ""
        .addRow(3)      // "3"
        .addRow(1)      // 1
        .addRow(0)      // 0
        .addRow(-300)   // -300
        .addRow((Long) null)   // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  /**
   * There are limits on Drill's generosity. If no conversion exists
   * to int, the query will fail with a descriptive error.
   */
  @Test
  public void testIntWithError() {
    String json =
        "{a: 1}\n{a: \"abc\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.open(json);
    try {
      loader.next();
      fail();
    } catch (UserException e) {

      // Robust check of error contents. Only need test once, error
      // code is generic
      String msg = e.getMessage();
      assertTrue(msg.contains("not compatible"));
      assertTrue(msg.contains("Column: a"));
      assertTrue(msg.contains("Column type: BIGINT"));
      assertTrue(msg.contains("JSON token type: string"));
      assertTrue(msg.contains("JSON token: abc"));
      assertTrue(msg.contains("Line: 2"));
    } finally {
      loader.close();
    }
  }

  @Test
  public void testFloat() {
    String json =
        "{a: 0.0} {a: 1.0} {a: 1.25} {a: -123.125} {a: null} " +
        "{a: -Infinity} {a: NaN} {a: Infinity} " +
        "{a: 0} {a: 12} " +
        "{a: true} {a: false} " +
        "{a: \"\"} {a: \"3.75\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allowNanInf = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.FLOAT8)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow(0.0)      // 0.0
        .addRow(1.0)      // 1.0
        .addRow(1.25)     // 1.25
        .addRow(-123.125) // -123.125
        .addRow((Double) null)   // null
        .addRow(Double.NEGATIVE_INFINITY) // -Inf
        .addRow(Double.NaN) // Nan
        .addRow(Double.POSITIVE_INFINITY) // Inf
        .addRow(0.0)      // 0
        .addRow(12.0)     // 12
        .addRow(1.0)      // true
        .addRow(0.0)      // false
        .addRow((Double) null)   // ""
        .addRow(3.75)     // "3.75"
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testAllTextFloat() {
    String json =
        "{a: 0.0} {a: 1.0} {a: 1.25} {a: -123.125} {a: null} " +
        "{a: -Infinity} {a: NaN} {a: Infinity}";

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allTextMode = true;
    loader.jsonOptions.allowNanInf = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow("0.0")
        .addRow("1.0")
        .addRow("1.25")
        .addRow("-123.125")
        .addRow((String) null)
        .addRow("-Infinity")
        .addRow("NaN")
        .addRow("Infinity")
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testFloatWithSchema() {
    String json =
        "{a: 0} {a: 12} " +
        "{a: true} {a: false} " +
        "{a: \"\"} {a: \"3.75\"} " +
        "{a: 0.0} {a: 1.0} {a: 1.25} {a: -123.125} {a: null} " +
        "{a: -Infinity} {a: NaN} {a: Infinity}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("a", MinorType.FLOAT8)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.jsonOptions.allowNanInf = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow(0.0)      // 0
        .addRow(12.0)     // 12
        .addRow(1.0)      // true
        .addRow(0.0)      // false
        .addRow((Double) null)   // ""
        .addRow(3.75)     // "3.75"
        .addRow(0.0)      // 0.0
        .addRow(1.0)      // 1.0
        .addRow(1.25)     // 1.25
        .addRow(-123.125) // -123.125
        .addRow((Double) null)   // null
        .addRow(Double.NEGATIVE_INFINITY) // -Inf
        .addRow(Double.NaN) // Nan
        .addRow(Double.POSITIVE_INFINITY) // Inf
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testFloatWithError() {
    String json =
        "{a: 1.25}\n{a: \"abc\"}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.open(json);
    try {
      loader.next();
      fail();
    } catch (UserException e) {
      String msg = e.getMessage();
      assertTrue(msg.contains("not compatible"));
      assertTrue(msg.contains("Column type: DOUBLE"));
    } finally {
      loader.close();
    }
  }

  @Test
  public void testString() {
    String json =
        "{a: \"\"} {a: \"foo\"} {a: \" bar \"} {a: null} " +
        "{a: 0} {a: 12} " +
        "{a: true} {a: false} " +
        "{a: 0.0} {a: 1.25}";
    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow("")       // ""
        .addRow("foo")    // "foo"
        .addRow(" bar ")  // " bar "
        .addRow((String) null) // null
        .addRow("0")      // 0
        .addRow("12")     // 12
        .addRow("true")   // true
        .addRow("false")  // false
        .addRow("0.0")    // 0.0
        .addRow("1.25")   // 1.25
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testAllTextString() {
    String json =
        "{a: \"\"} {a: \"foo\"} {a: \" bar \"} {a: null}";

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allTextMode = true;
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    TupleMetadata expectedSchema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();
    RowSet expected = fixture.rowSetBuilder(expectedSchema)
        .addRow("")       // ""
        .addRow("foo")    // "foo"
        .addRow(" bar ")  // " bar "
        .addRow((String) null) // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testStringWithSchema() {
    String json =
        "{a: 0} {a: 12} " +
        "{a: true} {a: false} " +
        "{a: 0.0} {a: 1.25} " +
        "{a: \"\"} {a: \"foo\"} {a: \" bar \"} {a: null}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("a", MinorType.VARCHAR)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow("0")      // 0
        .addRow("12")     // 12
        .addRow("true")   // true
        .addRow("false")  // false
        .addRow("0.0")    // 0.0
        .addRow("1.25")   // 1.25
        .addRow("")       // ""
        .addRow("foo")    // "foo"
        .addRow(" bar ")  // " bar "
        .addRow((String) null) // null
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testProvidedSchemaNumbers() {
    String json =

        // null is ambiguous
        "{s: null, i: null, bi: null, f4: null, f8: null, d: null}\n" +
        // Strings are also
        "{s: \"10\", i: \"10\", bi: \"10\", f4: \"10\", f8: \"10\", d: \"10\"}\n" +
        "{             f4: \"10.5\", f8: \"10.5\", d: \"10.5\"}\n" +
        "{             f4: \"-1e5\", f8: \"-1e5\", d: \"-1e5\"}\n" +

        // Float-only values
        "{             f4: \"NaN\", f8: \"NaN\"}\n" +
        "{             f4: \"Infinity\", f8: \"Infinity\"}\n" +
        "{             f4: \"-Infinity\", f8: \"-Infinity\"}\n" +

        // Large decimal
        "{d: \"123456789012345678901234.5678\" }\n" +

        // Ambiguous numbers
        "{s: 10, i: 10, bi: 10, f4: 10, f8: 10, d: 10}\n" +
        "{             f4: 10.5, f8: 10.5, d: 10.5}\n" +
        "{             f4: -1e5, f8: -1e5, d: -1e5}\n" +

        // Float-only values
        "{             f4: NaN, f8: NaN}\n" +
        "{             f4: Infinity, f8: Infinity}\n" +
        "{             f4: -Infinity, f8: -Infinity}\n" +

        // Large decimal
        "{d: 123456789012345678901234.5678 }\n";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("s", MinorType.SMALLINT)
        .addNullable("i", MinorType.INT)
        .addNullable("bi", MinorType.BIGINT)
        .addNullable("f4", MinorType.FLOAT4)
        .addNullable("f8", MinorType.FLOAT8)
        .addNullable("d", MinorType.VARDECIMAL, 38, 4)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.jsonOptions.allowNanInf = true;
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        //      s     i     bi    f4    f8    d
        .addRow(null, null, null, null, null, null)
        .addRow(10,   10,   10,   10,   10,   dec("10"))
        .addRow(null, null, null, 10.5, 10.5D, dec("10.5"))
        .addRow(null, null, null, -1e5,  -1e5D, dec("-1e5"))
        .addRow(null, null, null, Float.NaN, Double.NaN, null)
        .addRow(null, null, null, Float.POSITIVE_INFINITY, Double.POSITIVE_INFINITY, null)
        .addRow(null, null, null, Float.NEGATIVE_INFINITY, Double.NEGATIVE_INFINITY, null)
        .addRow(null, null, null, null, null, dec("123456789012345678901234.5678"))
        .addRow(10,   10,   10,   10,   10,   dec("10"))
        .addRow(null, null, null, 10.5, 10.5D, dec("10.5"))
        .addRow(null, null, null, -1e5,  -1e5D, dec("-1e5"))
        .addRow(null, null, null, Float.NaN, Double.NaN, null)
        .addRow(null, null, null, Float.POSITIVE_INFINITY, Double.POSITIVE_INFINITY, null)
        .addRow(null, null, null, Float.NEGATIVE_INFINITY, Double.NEGATIVE_INFINITY, null)
        .addRow(null, null, null, null, null, dec("123456789012345678901234.5678"))
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testProvidedSchemaWithDates() {
    LocalDateTime local = LocalDateTime.of(2020, 4, 21, 11, 22, 33, 456_000_000);
    LocalDateTime localEpoch = LocalDateTime.of(1970, 1, 1, 0, 0, 0);
    long localTs = Duration.between(localEpoch, local).toMillis();
    LocalDateTime localDate = LocalDateTime.of(2020, 4, 21, 0, 0, 0);
    long localDateTs = Duration.between(localEpoch, localDate).toMillis();
    int localTimeTs = (int) (localTs - localDateTs);
    String json =
        "{ts: null, d: null, t: null}\n" +
        "{ts: \"2020-04-21T11:22:33.456\", d: \"2020-04-21\", t: \"11:22:33.456\"}\n" +
        "{ts: " + localTs + ", d: " + localDateTs + ", t: " + localTimeTs + "}\n";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("ts", MinorType.TIMESTAMP)
        .addNullable("d", MinorType.DATE)
        .addNullable("t", MinorType.TIME)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow(null, null, null)
        .addRow(localTs, localDateTs, localTimeTs)
        .addRow(localTs, localDateTs, localTimeTs)
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testProvidedSchemaWithIntervals() {
    String json =
        "{i: null, iy: null, id: null}\n" +
        "{i: \"P1Y2M3DT4H5M6S\", iy: \"P1Y2M\", id: \"P3DT4H5M6S\"}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("i", MinorType.INTERVAL)
        .addNullable("iy", MinorType.INTERVALYEAR)
        .addNullable("id", MinorType.INTERVALDAY)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    org.joda.time.Period full = org.joda.time.Period.years(1).withMonths(2)
        .withDays(3).withHours(4).withMinutes(5).withSeconds(6);
    org.joda.time.Period ym = org.joda.time.Period.years(1).withMonths(2);
    org.joda.time.Period dhms = org.joda.time.Period.days(3).withHours(4)
        .withMinutes(5).withSeconds(6);
    RowSet expected = fixture.rowSetBuilder(schema)
        .addRow(null, null, null)
        .addRow(full, ym, dhms)
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }

  @Test
  public void testProvidedSchemaWithBinary() {
    String json =
        "{b: null}\n" +
        "{b: \"ZHJpbGw=\"}";
    TupleMetadata schema = new SchemaBuilder()
        .addNullable("b", MinorType.VARBINARY)
        .build();

    JsonLoaderFixture loader = new JsonLoaderFixture();
    loader.builder.providedSchema(schema);
    loader.open(json);
    RowSet results = loader.next();
    assertNotNull(results);

    byte[] bytes = "Drill".getBytes(StandardCharsets.UTF_8);
    RowSet expected = fixture.rowSetBuilder(schema)
        .addSingleCol(null)
        .addSingleCol(bytes)
        .build();
    RowSetUtilities.verify(expected, results);
    assertNull(loader.next());
    loader.close();
  }
}