| /* |
| * 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.segment.join.table; |
| |
| import it.unimi.dsi.fastutil.ints.IntList; |
| import org.apache.druid.java.util.common.IAE; |
| import org.apache.druid.java.util.common.io.Closer; |
| import org.apache.druid.segment.ColumnSelectorFactory; |
| import org.apache.druid.segment.ReferenceCountedObject; |
| import org.apache.druid.segment.column.RowSignature; |
| import org.apache.druid.segment.column.ValueType; |
| import org.apache.druid.segment.data.ReadableOffset; |
| |
| import javax.annotation.Nullable; |
| import java.io.Closeable; |
| import java.io.IOException; |
| import java.util.Set; |
| |
| /** |
| * An interface to a table where some columns (the 'key columns') have indexes that enable fast lookups. |
| * |
| * The main user of this class is {@link IndexedTableJoinable}, and its main purpose is to participate in joins. |
| */ |
| public interface IndexedTable extends ReferenceCountedObject, Closeable |
| { |
| /** |
| * Returns the version of this table, used to compare against when loading a new version of the table |
| */ |
| @SuppressWarnings("unused") |
| String version(); |
| |
| /** |
| * Returns the columns of this table that have indexes. |
| */ |
| Set<String> keyColumns(); |
| |
| /** |
| * Returns the signature of this table, which includes all key columns (as well as other columns that can be |
| * selected, but are not keys). |
| */ |
| RowSignature rowSignature(); |
| |
| /** |
| * Returns the number of rows in this table. It must not change over time, since it is used for things like algorithm |
| * selection and reporting of cardinality metadata. |
| */ |
| int numRows(); |
| |
| /** |
| * Returns the index for a particular column. The provided column number must be that column's position in |
| * {@link #rowSignature()}. |
| */ |
| Index columnIndex(int column); |
| |
| /** |
| * Returns a reader for a particular column. The provided column number must be that column's position in |
| * {@link #rowSignature()}. Don't forget to close your {@link Reader} when finished reading, to clean up any |
| * resources. |
| */ |
| Reader columnReader(int column); |
| |
| /** |
| * This method allows a table to directly provide an optimized {@link ColumnSelectorFactory} for |
| * {@link IndexedTableJoinMatcher} to create selectors. If this method returns null, the default |
| * {@link IndexedTableColumnSelectorFactory}, which creates {@link IndexedTableDimensionSelector} or |
| * {@link IndexedTableColumnValueSelector} as appropriate, both backed with a {@link #columnReader}, will be used |
| * instead. |
| */ |
| @Nullable |
| default ColumnSelectorFactory makeColumnSelectorFactory(ReadableOffset offset, boolean descending, Closer closer) |
| { |
| return null; |
| } |
| |
| /** |
| * Computes a {@code byte[]} key for the table that can be used for computing cache keys for join operations. |
| * see {@link org.apache.druid.segment.join.JoinableFactory#computeJoinCacheKey} |
| * |
| * @return the byte array for cache key |
| * @throws {@link IAE} if caching is not supported |
| */ |
| default byte[] computeCacheKey() |
| { |
| throw new IAE("Caching is not supported. Check `isCacheable` before calling computeCacheKey"); |
| } |
| |
| /** |
| * Returns whether this indexed table can be cached for the join operations |
| */ |
| default boolean isCacheable() |
| { |
| return false; |
| } |
| |
| /** |
| * Indexes support fast lookups on key columns. |
| */ |
| interface Index |
| { |
| int NOT_FOUND = -1; |
| |
| /** |
| * Returns the natural key type for the index. |
| */ |
| ValueType keyType(); |
| |
| /** |
| * Returns whether keys are unique in this index. If this returns true, then {@link #find(Object)} will only ever |
| * return a zero- or one-element list. |
| */ |
| boolean areKeysUnique(); |
| |
| /** |
| * Returns the list of row numbers corresponding to "key" in this index. |
| * |
| * If "key" is some type other than the natural type {@link #keyType()}, it will be converted before checking |
| * the index. |
| */ |
| IntList find(Object key); |
| |
| /** |
| * Returns the row number corresponding to "key" in this index, or {@link #NOT_FOUND} if the key does not exist |
| * in the index. |
| * |
| * It is only valid to call this method if {@link #keyType()} is {@link ValueType#LONG} and {@link #areKeysUnique()} |
| * returns true. |
| * |
| * @throws UnsupportedOperationException if preconditions are not met |
| */ |
| int findUniqueLong(long key); |
| } |
| |
| /** |
| * Readers support reading values out of any column. |
| */ |
| interface Reader extends Closeable |
| { |
| /** |
| * Read the value at a particular row number. Throws an exception if the row is out of bounds (must be between zero |
| * and {@link #numRows()}). |
| */ |
| @Nullable |
| Object read(int row); |
| |
| @Override |
| default void close() throws IOException |
| { |
| // nothing to close |
| } |
| } |
| } |