| /* |
| * 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.query.lookup; |
| |
| |
| import com.fasterxml.jackson.annotation.JsonSubTypes; |
| import com.fasterxml.jackson.annotation.JsonTypeInfo; |
| import org.apache.druid.query.extraction.MapLookupExtractor; |
| |
| import javax.annotation.Nullable; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| |
| @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type") |
| @JsonSubTypes(value = { |
| @JsonSubTypes.Type(name = "map", value = MapLookupExtractor.class) |
| }) |
| public abstract class LookupExtractor |
| { |
| /** |
| * Apply a particular lookup methodology to the input string |
| * |
| * @param key The value to apply the lookup to. |
| * |
| * @return The lookup, or null when key is `null` or cannot have the lookup applied to it and should be treated as missing. |
| */ |
| @Nullable |
| public abstract String apply(@Nullable String key); |
| |
| /** |
| * @param keys set of keys to apply lookup for each element |
| * |
| * @return Returns {@link Map} whose keys are the contents of {@code keys} and whose values are computed on demand using lookup function {@link #unapply(String)} |
| * or empty map if {@code values} is `null` |
| * User can override this method if there is a better way to perform bulk lookup |
| */ |
| |
| public Map<String, String> applyAll(Iterable<String> keys) |
| { |
| if (keys == null) { |
| return Collections.emptyMap(); |
| } |
| Map<String, String> map = new HashMap<>(); |
| for (String key : keys) { |
| map.put(key, apply(key)); |
| } |
| return map; |
| } |
| |
| /** |
| * Provide the reverse mapping from a given value to a list of keys |
| * |
| * @param value the value to apply the reverse lookup |
| * |
| * @return the list of keys that maps to value or empty list. |
| * Note that for the case of a none existing value in the lookup we have to cases either return an empty list OR list with null element. |
| * returning an empty list implies that user want to ignore such a lookup value. |
| * In the other hand returning a list with the null element implies user want to map the none existing value to the key null. |
| * Null value maps to empty list. |
| */ |
| |
| public abstract List<String> unapply(@Nullable String value); |
| |
| /** |
| * @param values Iterable of values for which will perform reverse lookup |
| * |
| * @return Returns {@link Map} whose keys are the contents of {@code values} and whose values are computed on demand using the reverse lookup function {@link #unapply(String)} |
| * or empty map if {@code values} is `null` |
| * User can override this method if there is a better way to perform bulk reverse lookup |
| */ |
| |
| public Map<String, List<String>> unapplyAll(Iterable<String> values) |
| { |
| if (values == null) { |
| return Collections.emptyMap(); |
| } |
| Map<String, List<String>> map = new HashMap<>(); |
| for (String value : values) { |
| map.put(value, unapply(value)); |
| } |
| return map; |
| } |
| |
| /** |
| * Returns true if this lookup extractor's {@link #iterable()} method will return a valid iterator. |
| */ |
| public abstract boolean canIterate(); |
| |
| /** |
| * Returns true if this lookup extractor's {@link #keySet()} method will return a valid set. |
| */ |
| public abstract boolean canGetKeySet(); |
| |
| /** |
| * Returns an Iterable that iterates over the keys and values in this lookup extractor. |
| * |
| * @throws UnsupportedOperationException if {@link #canIterate()} returns false. |
| */ |
| public abstract Iterable<Map.Entry<String, String>> iterable(); |
| |
| /** |
| * Returns a Set of all keys in this lookup extractor. The returned Set will not change. |
| * |
| * @throws UnsupportedOperationException if {@link #canGetKeySet()} returns false. |
| */ |
| public abstract Set<String> keySet(); |
| |
| /** |
| * Create a cache key for use in results caching |
| * |
| * @return A byte array that can be used to uniquely identify if results of a prior lookup can use the cached values |
| */ |
| public abstract byte[] getCacheKey(); |
| |
| // make this abstract again once @drcrallen fix the metmax lookup implementation. |
| public boolean isOneToOne() |
| { |
| return false; |
| } |
| } |