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

Example 1 with SimpleListShim

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

the class ListState method addSecondType.

/**
 * Perform the delicate dance of promoting a list vector from a single type to
 * a union, while leaving the writer client blissfully ignorant that the underlying
 * vector representation just did a radical change. Key tasks:
 * <ul>
 * <li>Create the new column (type member) requested by the client.</li>
 * <li>The List vector currently has a single type. Promote the list to
 * a union, adding the existing type (column) as the first union member.</li>
 * <li>Initialize the union's type vector with either the type of the existing
 * column, or null, depending on the setting of the is-set bits in the existing
 * column vector.</li>
 * <li>Since we've written values into the union's type vector, mark the
 * last-write position in the union vector's type vector writer to reflect
 * these writes. (Otherwise, the writer will helpfully zero-fill the previous
 * positions as part of it's back-fill handling.</li>
 * <li>Replace the single-type shim in the union vector with a full union
 * shim.</li>
 * <li>Move the existing column writer or the member column across from the
 * single-writer shim to the new union shim.</li>
 * <li>Augment the list vector's vector state to include a vector state for
 * the newly created union vector.</li>
 * </ul>
 * <p>
 * Here, yet again, an editorial comment might be useful. List vectors are
 * very strange and not at all well designed for high-speed writing. They are
 * too complex; too much can go wrong and there are too many states to handle.
 * Not only that, variant types don't play well with a relational model like
 * SQL. This code works, but the overall list concept really needs rethinking.
 *
 * @param colState the column state for the newly added type column; the
 * one causing the list to change from single-type to a union
 */
private void addSecondType(ColumnState colState) {
    final UnionWriterImpl unionWriter = unionWriter();
    final ListVector listVector = listVector();
    // Going from one type to a union
    // Convert the list from single type to a union,
    // moving across the previous type vector.
    final int typeFillCount = unionWriter.elementPosition().writeIndex();
    final UnionVector unionVector = listVector.convertToUnion(innerCardinality(), typeFillCount);
    unionVector.addType(colState.vector());
    // Replace the single-type shim with a union shim, copying
    // across the existing writer.
    final SimpleListShim oldShim = (SimpleListShim) unionWriter.shim();
    final UnionVectorShim newShim = new UnionVectorShim(unionVector);
    unionWriter.bindShim(newShim);
    newShim.addMemberWriter(oldShim.memberWriter());
    newShim.initTypeIndex(typeFillCount);
    // The union vector will be managed within the list vector state.
    // (Do this last because the union vector state expects the union
    // writer to be operating in "union mode".
    listVectorState().replaceMember(new UnionVectorState(unionVector, unionWriter));
}

Example 2 with SimpleListShim

use of org.apache.drill.exec.vector.accessor.writer.SimpleListShim 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);
}

Example 3 with SimpleListShim

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

the class ListState method addFirstType.

private void addFirstType(ColumnState colState) {
    // Going from no types to one type.
    // Add the member to the list as its data vector.
    listVector().setChildVector(colState.vector());
    // Don't add the type to the vector state; we manage it as part
    // of the collection of member columns.
    // Note that we may have written 1 or more nulls to the array
    // before we make this 0-to-1 type transition. If the new type is
    // a scalar, it is nullable. Automatic back-fill will fill prior values
    // with null, so there is nothing to do here.
    // 
    // Note, however, that if this first type is a map, there is no way
    // to mark that map as null; we loose the nullability state. However,
    // if we later promote the single-type map to a union, we can't
    // recover the null states and so the previously-null values won't
    // be null. We could fix this, for a single batch, by keeping track
    // of the null positions. But, there is no way to mark later maps
    // as null. Another choice would be to force a transition directly
    // to a union if the first type is a map. None of this has ever worked
    // and so is left as an exercise for later once we work out what we
    // actually want to support.
    // Create the single type shim.
    unionWriter().bindShim(new SimpleListShim());
}