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A module that is everything required to understands Druid Segments
/*
* 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.druid.frame.write.columnar;
import org.apache.druid.frame.allocation.MemoryAllocator;
import org.apache.druid.frame.write.UnsupportedColumnTypeException;
import org.apache.druid.java.util.common.ISE;
import org.apache.druid.query.dimension.DefaultDimensionSpec;
import org.apache.druid.segment.ColumnSelectorFactory;
import org.apache.druid.segment.ColumnValueSelector;
import org.apache.druid.segment.DimensionSelector;
import org.apache.druid.segment.column.ColumnCapabilities;
import org.apache.druid.segment.column.ColumnType;
import org.apache.druid.segment.serde.ComplexMetricSerde;
import org.apache.druid.segment.serde.ComplexMetrics;
import javax.annotation.Nullable;
public class FrameColumnWriters
{
public static final byte TYPE_LONG = 1;
public static final byte TYPE_FLOAT = 2;
public static final byte TYPE_DOUBLE = 3;
public static final byte TYPE_STRING = 4;
public static final byte TYPE_COMPLEX = 5;
public static final byte TYPE_STRING_ARRAY = 6;
private FrameColumnWriters()
{
// No instantiation.
}
/**
* Helper used by {@link ColumnarFrameWriterFactory}.
*
* @throws UnsupportedColumnTypeException if "type" cannot be handled
*/
static FrameColumnWriter create(
final ColumnSelectorFactory columnSelectorFactory,
final MemoryAllocator allocator,
final String column,
final ColumnType type
)
{
if (type == null) {
throw new UnsupportedColumnTypeException(column, null);
}
switch (type.getType()) {
case LONG:
return makeLongWriter(columnSelectorFactory, allocator, column);
case FLOAT:
return makeFloatWriter(columnSelectorFactory, allocator, column);
case DOUBLE:
return makeDoubleWriter(columnSelectorFactory, allocator, column);
case STRING:
return makeStringWriter(columnSelectorFactory, allocator, column);
case ARRAY:
switch (type.getElementType().getType()) {
case STRING:
return makeStringArrayWriter(columnSelectorFactory, allocator, column);
default:
throw new UnsupportedColumnTypeException(column, type);
}
case COMPLEX:
return makeComplexWriter(columnSelectorFactory, allocator, column, type.getComplexTypeName());
default:
throw new UnsupportedColumnTypeException(column, type);
}
}
private static LongFrameColumnWriter makeLongWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName
)
{
final ColumnCapabilities capabilities = selectorFactory.getColumnCapabilities(columnName);
final ColumnValueSelector selector = selectorFactory.makeColumnValueSelector(columnName);
return new LongFrameColumnWriter(selector, allocator, hasNullsForNumericWriter(capabilities));
}
private static FloatFrameColumnWriter makeFloatWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName
)
{
final ColumnCapabilities capabilities = selectorFactory.getColumnCapabilities(columnName);
final ColumnValueSelector selector = selectorFactory.makeColumnValueSelector(columnName);
return new FloatFrameColumnWriter(selector, allocator, hasNullsForNumericWriter(capabilities));
}
private static DoubleFrameColumnWriter makeDoubleWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName
)
{
final ColumnCapabilities capabilities = selectorFactory.getColumnCapabilities(columnName);
final ColumnValueSelector selector = selectorFactory.makeColumnValueSelector(columnName);
return new DoubleFrameColumnWriter(selector, allocator, hasNullsForNumericWriter(capabilities));
}
private static StringFrameColumnWriter makeStringWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName
)
{
final ColumnCapabilities capabilities = selectorFactory.getColumnCapabilities(columnName);
final DimensionSelector selector = selectorFactory.makeDimensionSelector(DefaultDimensionSpec.of(columnName));
return new StringFrameColumnWriterImpl(
selector,
allocator,
capabilities == null || capabilities.hasMultipleValues().isMaybeTrue()
);
}
private static StringFrameColumnWriter makeStringArrayWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName
)
{
final ColumnValueSelector selector = selectorFactory.makeColumnValueSelector(columnName);
return new StringArrayFrameColumnWriterImpl(selector, allocator);
}
private static ComplexFrameColumnWriter makeComplexWriter(
final ColumnSelectorFactory selectorFactory,
final MemoryAllocator allocator,
final String columnName,
@Nullable final String columnTypeName
)
{
if (columnTypeName == null) {
throw new ISE("No complexTypeName, cannot write column [%s]", columnName);
}
final ComplexMetricSerde serde = ComplexMetrics.getSerdeForType(columnTypeName);
if (serde == null) {
throw new ISE("No serde for complexTypeName[%s], cannot write column [%s]", columnTypeName, columnName);
}
final ColumnValueSelector selector = selectorFactory.makeColumnValueSelector(columnName);
return new ComplexFrameColumnWriter(selector, allocator, serde);
}
private static boolean hasNullsForNumericWriter(final ColumnCapabilities capabilities)
{
if (capabilities == null) {
return true;
} else if (capabilities.getType().isNumeric()) {
return capabilities.hasNulls().isMaybeTrue();
} else {
// Reading
return true;
}
}
}