Examples with EmptyListShim org.apache.drill.exec.vector.accessor.writer.EmptyListShim used on opensource projects

Example 1 with EmptyListShim

use of org.apache.drill.exec.vector.accessor.writer.EmptyListShim in project drill by apache.

the class ColumnBuilder method buildUnionList.

/**
 * Create a list based on a (possible) union. The list starts empty here. The client
 * can then add types as they are discovered. The list itself will transition from a
 * list of nulls (no child type), to a list of a single type, to a list of unions.
 * The writer interface will consistently present the list as a list of unions, even
 * when the list itself has no subtype or a single subtype.
 * <p>
 * List vectors (lists of unions) are not supported in
 * Drill. The code here works up through the scan operator. But, other operators do
 * not support the {@code ListVector} type.
 *
 * @param parent the parent (tuple, union or list) that holds this list
 * @param columnSchema description of the list (must be empty of
 * subtypes)
 * @return the column state for the list
 */
private ColumnState buildUnionList(ContainerState parent, ColumnMetadata columnSchema) {
    // The variant must start out empty.
    assert columnSchema.variantSchema().size() == 0;
    // Create the union writer, bound to an empty list shim.
    final UnionWriterImpl unionWriter = new UnionWriterImpl(columnSchema);
    unionWriter.bindShim(new EmptyListShim());
    final VariantObjectWriter unionObjWriter = new VariantObjectWriter(unionWriter);
    // Create the list vector. Starts with the default (dummy) data
    // vector which corresponds to the empty union shim above.
    // Don't get the list vector from the vector cache. List vectors may
    // have content that varies from batch to batch. Only the leaf
    // vectors can be cached.
    final ListVector listVector = new ListVector(columnSchema.schema(), parent.loader().allocator(), null);
    // Create the list vector state that tracks the list vector lifecycle.
    final ListVectorState vectorState = new ListVectorState(unionWriter, listVector);
    // Create the list writer: an array of unions.
    final AbstractObjectWriter listWriter = new ArrayObjectWriter(new ListWriterImpl(columnSchema, listVector, unionObjWriter));
    // Create the manager for the columns within the list (which may or
    // may not be grouped into a union.)
    final ListState listState = new ListState(parent.loader(), parent.vectorCache().childCache(columnSchema.name()));
    // Bind the union state to the union writer to handle column additions.
    unionWriter.bindListener(listState);
    // Assemble it all into a union column state.
    return new UnionColumnState(parent.loader(), listWriter, vectorState, listState);
}

Example 2 with EmptyListShim

use of org.apache.drill.exec.vector.accessor.writer.EmptyListShim in project drill by apache.

the class TestResultSetLoaderUnions method testVariantListDynamic.

/**
 * Test a variant list created dynamically at load time.
 * The list starts with no type, at which time it can hold
 * only null values. Then we add a Varchar, and finally an
 * Int.
 * <p>
 * This test is superficial. There are many odd cases to consider.
 * <ul>
 * <li>Write nulls to a list with no type. (This test ensures that
 * adding a (nullable) scalar "does the right thing."</li>
 * <li>Add a map to the list. Maps carry no "bits" vector, so null
 * list entries to that point are lost. (For maps, we could go straight
 * to a union, with just a map, to preserve the null states. This whole
 * area is a huge mess...)</li>
 * <li>Do the type transitions when writing to a row. (The tests here
 * do the transition between rows.)</li>
 * </ul>
 *
 * The reason for the sparse coverage is that Drill barely supports lists
 * and unions; most code is just plain broken. Our goal here is not to fix
 * all those problems, just to leave things no more broken than before.
 */
@Test
public void testVariantListDynamic() {
    final ResultSetLoader rsLoader = new ResultSetLoaderImpl(fixture.allocator());
    final RowSetLoader writer = rsLoader.writer();
    // Can write a batch as if this was a repeated Varchar, except
    // that any value can also be null.
    rsLoader.startBatch();
    writer.addColumn(MaterializedField.create("id", Types.required(MinorType.INT)));
    writer.addColumn(MaterializedField.create("list", Types.optional(MinorType.LIST)));
    // Sanity check: should be an array of variants because we said the
    // types within the list are expandable (which is the default.)
    final ArrayWriter arrWriter = writer.array("list");
    assertEquals(ObjectType.VARIANT, arrWriter.entryType());
    final VariantWriter variant = arrWriter.variant();
    // We need to verify that the internal state is what we expect, so
    // the next assertion peeks inside the private bits of the union
    // writer. No client code should ever need to do this, of course.
    assertTrue(((UnionWriterImpl) variant).shim() instanceof EmptyListShim);
    // No types, so all we can do is add a null list, or a list of nulls.
    writer.addRow(1, null).addRow(2, variantArray()).addRow(3, variantArray(null, null));
    // Add a String. Now we can create a list of strings and/or nulls.
    variant.addMember(MinorType.VARCHAR);
    assertTrue(variant.hasType(MinorType.VARCHAR));
    // Sanity check: sniff inside to ensure that the list contains a single
    // type.
    assertTrue(((UnionWriterImpl) variant).shim() instanceof SimpleListShim);
    assertTrue(((ListWriterImpl) arrWriter).vector().getDataVector() instanceof NullableVarCharVector);
    writer.addRow(4, variantArray("fred", null, "barney"));
    // Add an integer. The list vector should be promoted to union.
    // Now we can add both types.
    variant.addMember(MinorType.INT);
    // Sanity check: sniff inside to ensure promotion to union occurred
    assertTrue(((UnionWriterImpl) variant).shim() instanceof UnionVectorShim);
    assertTrue(((ListWriterImpl) arrWriter).vector().getDataVector() instanceof UnionVector);
    writer.addRow(5, variantArray("wilma", null, 30));
    // Verify
    final RowSet result = fixture.wrap(rsLoader.harvest());
    final TupleMetadata schema = new SchemaBuilder().add("id", MinorType.INT).addList("list").addType(MinorType.VARCHAR).addType(MinorType.INT).resumeSchema().buildSchema();
    final SingleRowSet expected = fixture.rowSetBuilder(schema).addRow(1, null).addRow(2, variantArray()).addRow(3, variantArray(null, null)).addRow(4, variantArray("fred", null, "barney")).addRow(5, variantArray("wilma", null, 30)).build();
    RowSetUtilities.verify(expected, result);
}