richardstartin commented on a change in pull request #7405: URL: https://github.com/apache/pinot/pull/7405#discussion_r710143588
########## File path: pinot-segment-local/src/main/java/org/apache/pinot/segment/local/utils/nativefst/utils/RegexpMatcher.java ########## @@ -0,0 +1,170 @@ +/** + * 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.pinot.segment.local.utils.nativefst.utils; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.Iterator; +import java.util.List; +import java.util.Set; +import org.apache.pinot.segment.local.utils.nativefst.FST; +import org.apache.pinot.segment.local.utils.nativefst.automaton.Automaton; +import org.apache.pinot.segment.local.utils.nativefst.automaton.CharacterRunAutomaton; +import org.apache.pinot.segment.local.utils.nativefst.automaton.RegExp; +import org.apache.pinot.segment.local.utils.nativefst.automaton.State; +import org.apache.pinot.segment.local.utils.nativefst.automaton.Transition; + + +/** + * RegexpMatcher is a helper to retrieve matching values for a given regexp query. + * Regexp query is converted into an automaton and we run the matching algorithm on FST. + * + * Two main functions of this class are + * regexMatchOnFST() Function runs matching on FST (See function comments for more details) + * match(input) Function builds the automaton and matches given input. + */ +public class RegexpMatcher { + private final String _regexQuery; + private final FST _fst; + private final Automaton _automaton; + + public RegexpMatcher(String regexQuery, FST fst) { + _regexQuery = regexQuery; + _fst = fst; + + _automaton = new RegExp(_regexQuery).toAutomaton(); + } + + public static List<Long> regexMatch(String regexQuery, FST fst) { + RegexpMatcher matcher = new RegexpMatcher(regexQuery, fst); + return matcher.regexMatchOnFST(); + } + + // Matches "input" string with _regexQuery Automaton. + public boolean match(String input) { + CharacterRunAutomaton characterRunAutomaton = new CharacterRunAutomaton(_automaton); + return characterRunAutomaton.run(input); + } + + /** + * This function runs matching on automaton built from regexQuery and the FST. + * FST stores key (string) to a value (Long). Both are state machines and state transition is based on + * a input character. + * + * This algorithm starts with Queue containing (Automaton Start Node, FST Start Node). + * Each step an entry is popped from the queue: + * 1) if the automaton state is accept and the FST Node is final (i.e. end node) then the value stored for that FST + * is added to the set of result. + * 2) Else next set of transitions on automaton are gathered and for each transition target node for that character + * is figured out in FST Node, resulting pair of (automaton state, fst node) are added to the queue. + * 3) This process is bound to complete since we are making progression on the FST (which is a DAG) towards final + * nodes. + * @return + */ + public List<Long> regexMatchOnFST() { + final List<Path> queue = new ArrayList<>(); + final List<Long> endNodes = new ArrayList<>(); + + if (_automaton.getNumberOfStates() == 0) { + return Collections.emptyList(); + } + + // Automaton start state and FST start node is added to the queue. + queue.add(new Path(_automaton.getInitialState(), _fst.getRootNode(), 0, new ArrayList<>())); + + Set<State> acceptStates = _automaton.getAcceptStates(); + while (queue.size() != 0) { + final Path path = queue.remove(queue.size() - 1); + + // If automaton is in accept state and the fstNode is final (i.e. end node) then add the entry to endNodes which + // contains the result set. + if (acceptStates.contains(path._state)) { + if (_fst.isArcFinal(path._fstArc)) { + endNodes.add((long) _fst.getOutputSymbol(path._fstArc)); Review comment: Why cast to `long` here? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For additional commands, e-mail: commits-h...@pinot.apache.org
