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https://issues.apache.org/jira/browse/FLINK-7147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16103173#comment-16103173
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ASF GitHub Bot commented on FLINK-7147:
---------------------------------------
Github user dianfu commented on a diff in the pull request:
https://github.com/apache/flink/pull/4296#discussion_r129832284
--- Diff:
flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/GreedyITCase.java
---
@@ -0,0 +1,290 @@
+/*
+ * 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.flink.cep.nfa;
+
+import org.apache.flink.cep.Event;
+import org.apache.flink.cep.nfa.compiler.NFACompiler;
+import org.apache.flink.cep.pattern.Pattern;
+import org.apache.flink.cep.pattern.conditions.SimpleCondition;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.util.TestLogger;
+
+import com.google.common.collect.Lists;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.apache.flink.cep.nfa.NFATestUtilities.compareMaps;
+import static org.apache.flink.cep.nfa.NFATestUtilities.feedNFA;
+
+/**
+ * IT tests covering {@link Pattern#greedy()}.
+ */
+public class GreedyITCase extends TestLogger {
+
+ @Test
+ public void testGreedyFollowedBy() {
+ List<StreamRecord<Event>> inputEvents = new ArrayList<>();
+
+ Event c = new Event(40, "c", 1.0);
+ Event a1 = new Event(41, "a", 2.0);
+ Event a2 = new Event(42, "a", 2.0);
+ Event a3 = new Event(43, "a", 2.0);
+ Event d = new Event(44, "d", 3.0);
+
+ inputEvents.add(new StreamRecord<>(c, 1));
+ inputEvents.add(new StreamRecord<>(a1, 2));
+ inputEvents.add(new StreamRecord<>(a2, 3));
+ inputEvents.add(new StreamRecord<>(a3, 4));
+ inputEvents.add(new StreamRecord<>(d, 5));
+
+ // c a* d
+ Pattern<Event, ?> pattern =
Pattern.<Event>begin("start").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("c");
+ }
+ }).followedBy("middle").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("a");
+ }
+ }).oneOrMore().optional().greedy().followedBy("end").where(new
SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("d");
+ }
+ });
+
+ NFA<Event> nfa = NFACompiler.compile(pattern,
Event.createTypeSerializer(), false);
+
+ final List<List<Event>> resultingPatterns =
feedNFA(inputEvents, nfa);
+
+ compareMaps(resultingPatterns, Lists.<List<Event>>newArrayList(
+ Lists.newArrayList(c, a1, a2, a3, d)
+ ));
+ }
+
+ @Test
+ public void testGreedyUtil() {
+ List<StreamRecord<Event>> inputEvents = new ArrayList<>();
+
+ Event c = new Event(40, "c", 1.0);
+ Event a1 = new Event(41, "a", 2.0);
+ Event a2 = new Event(42, "a", 3.0);
+ Event a3 = new Event(43, "a", 4.0);
+ Event d = new Event(44, "d", 3.0);
+
+ inputEvents.add(new StreamRecord<>(c, 1));
+ inputEvents.add(new StreamRecord<>(a1, 2));
+ inputEvents.add(new StreamRecord<>(a2, 3));
+ inputEvents.add(new StreamRecord<>(a3, 4));
+ inputEvents.add(new StreamRecord<>(d, 5));
+
+ // c a* d
+ Pattern<Event, ?> pattern =
Pattern.<Event>begin("start").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("c");
+ }
+ }).followedBy("middle").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("a");
+ }
+ }).oneOrMore().optional().greedy().until(new
SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getPrice() > 3.0;
+ }
+ }).followedBy("end").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("d");
+ }
+ });
+
+ NFA<Event> nfa = NFACompiler.compile(pattern,
Event.createTypeSerializer(), false);
+
+ final List<List<Event>> resultingPatterns =
feedNFA(inputEvents, nfa);
+
+ compareMaps(resultingPatterns, Lists.<List<Event>>newArrayList(
+ Lists.newArrayList(c, a1, a2, d)
+ ));
+ }
+
+ @Test
+ public void testEndWithGreedy() {
+ List<StreamRecord<Event>> inputEvents = new ArrayList<>();
+
+ Event c = new Event(40, "c", 1.0);
+ Event a1 = new Event(41, "a", 2.0);
+ Event a2 = new Event(42, "a", 2.0);
+ Event a3 = new Event(43, "a", 2.0);
+ Event d = new Event(44, "d", 2.0);
+
+ inputEvents.add(new StreamRecord<>(c, 1));
+ inputEvents.add(new StreamRecord<>(a1, 2));
+ inputEvents.add(new StreamRecord<>(a2, 3));
+ inputEvents.add(new StreamRecord<>(a3, 4));
+ inputEvents.add(new StreamRecord<>(d, 5));
+
+ // c a*
+ Pattern<Event, ?> pattern =
Pattern.<Event>begin("start").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("c");
+ }
+ }).followedBy("end").where(new SimpleCondition<Event>() {
+ private static final long serialVersionUID =
5726188262756267490L;
+
+ @Override
+ public boolean filter(Event value) throws Exception {
+ return value.getName().equals("a");
+ }
+ }).oneOrMore().optional().greedy();
+
+ NFA<Event> nfa = NFACompiler.compile(pattern,
Event.createTypeSerializer(), false);
+
+ final List<List<Event>> resultingPatterns =
feedNFA(inputEvents, nfa);
+
+ compareMaps(resultingPatterns, Lists.<List<Event>>newArrayList(
+ Lists.newArrayList(c, a1, a2, a3)
--- End diff --
I agree with you. If the greedy state is last state of the NFA, it will
make no difference whether it is greedy or not. What about only allowing greedy
state for the last state if its InnerConsumingStrategy is STRICT? In this
case, we can edit results once encountering an event not meeting the conditions.
> Support greedy quantifier in CEP
> --------------------------------
>
> Key: FLINK-7147
> URL: https://issues.apache.org/jira/browse/FLINK-7147
> Project: Flink
> Issue Type: Sub-task
> Components: CEP, Table API & SQL
> Reporter: Dian Fu
> Assignee: Dian Fu
>
> Greedy quantifier will try to match the token as many times as possible. For
> example, for pattern {{a b* c}} (skip till next is used) and inputs {{a b1 b2
> c}}, if the quantifier for {{b}} is greedy, it will only output {{a b1 b2 c}}.
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