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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-10414) Add skip to next strategy
Date Mon, 01 Oct 2018 09:41:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-10414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16633773#comment-16633773
] 

ASF GitHub Bot commented on FLINK-10414:
----------------------------------------

dawidwys closed pull request #6756: [FLINK-10414][cep] Added skip to next strategy
URL: https://github.com/apache/flink/pull/6756
 
 
   

This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:

As this is a foreign pull request (from a fork), the diff is supplied
below (as it won't show otherwise due to GitHub magic):

diff --git a/docs/dev/libs/cep.md b/docs/dev/libs/cep.md
index d7f915fc62e..c8e836349ef 100644
--- a/docs/dev/libs/cep.md
+++ b/docs/dev/libs/cep.md
@@ -1288,6 +1288,15 @@ For example, for a given pattern `b+ c` and a data stream `b1 b2 b3
c`, the diff
         </td>
         <td>After found matching <code>b1 b2 b3 c</code>, the match process
will not discard any result.</td>
     </tr>
+    <tr>
+        <td><strong>SKIP_TO_NEXT</strong></td>
+        <td>
+            <code>b1 b2 b3 c</code><br>
+            <code>b2 b3 c</code><br>
+            <code>b3 c</code><br>
+        </td>
+        <td>After found matching <code>b1 b2 b3 c</code>, the match process
will not discard any result, because no other match could start at b1.</td>
+    </tr>
     <tr>
         <td><strong>SKIP_PAST_LAST_EVENT</strong></td>
         <td>
@@ -1296,7 +1305,7 @@ For example, for a given pattern `b+ c` and a data stream `b1 b2 b3
c`, the diff
         <td>After found matching <code>b1 b2 b3 c</code>, the match process
will discard all started partial matches.</td>
     </tr>
     <tr>
-        <td><strong>SKIP_TO_FIRST</strong>[<code>b*</code>]</td>
+        <td><strong>SKIP_TO_FIRST</strong>[<code>b</code>]</td>
         <td>
             <code>b1 b2 b3 c</code><br>
             <code>b2 b3 c</code><br>
@@ -1340,7 +1349,35 @@ Pattern: `(a | c) (b | c) c+.greedy d` and sequence: `a b c1 c2 c3
d` Then the r
             <code>a b c1 c2 c3 d</code><br>
             <code>c1 c2 c3 d</code><br>
         </td>
-        <td>After found matching <code>a b c1 c2 c3 d</code>, the match
process will try to discard all partial matches started before <code>c1</code>.
There is one such match <code>b c1 c2 c3 d</code>.</td>
+        <td>After found matching <code>a b c1 c2 c3 d</code>, the match
process will discard all partial matches started before <code>c1</code>. There
is one such match <code>b c1 c2 c3 d</code>.</td>
+    </tr>
+</table>
+
+To better understand the difference between NO_SKIP and SKIP_TO_NEXT take a look at following
example:
+Pattern: `a b+` and sequence: `a b1 b2 b3` Then the results will be:
+
+
+<table class="table table-bordered">
+    <tr>
+        <th class="text-left" style="width: 25%">Skip Strategy</th>
+        <th class="text-center" style="width: 25%">Result</th>
+        <th class="text-center"> Description</th>
+    </tr>
+    <tr>
+        <td><strong>NO_SKIP</strong></td>
+        <td>
+            <code>a b1</code><br>
+            <code>a b1 b2</code><br>
+            <code>a b1 b2 b3</code><br>
+        </td>
+        <td>After found matching <code>a b1</code>, the match process will
not discard any result.</td>
+    </tr>
+    <tr>
+        <td><strong>SKIP_TO_NEXT</strong>[<code>b*</code>]</td>
+        <td>
+            <code>a b1</code><br>
+        </td>
+        <td>After found matching <code>a b1</code>, the match process will
discard all partial matches started at <code>a</code>. This means neither <code>a
b1 b2</code> nor <code>a b1 b2 b3</code> could be generated.</td>
     </tr>
 </table>
 
@@ -1354,6 +1391,10 @@ To specify which skip strategy to use, just create an `AfterMatchSkipStrategy`
b
         <td><code>AfterMatchSkipStrategy.noSkip()</code></td>
         <td>Create a <strong>NO_SKIP</strong> skip strategy </td>
     </tr>
+    <tr>
+        <td><code>AfterMatchSkipStrategy.skipToNext()</code></td>
+        <td>Create a <strong>SKIP_TO_NEXT</strong> skip strategy </td>
+    </tr>
     <tr>
         <td><code>AfterMatchSkipStrategy.skipPastLastEvent()</code></td>
         <td>Create a <strong>SKIP_PAST_LAST_EVENT</strong> skip strategy
</td>
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/AfterMatchSkipStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/AfterMatchSkipStrategy.java
index f4448a35560..7578e29bbfa 100644
--- a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/AfterMatchSkipStrategy.java
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/AfterMatchSkipStrategy.java
@@ -38,7 +38,7 @@
 	private static final long serialVersionUID = -4048930333619068531L;
 
 	/**
-	 * Discards every partial match that contains event of the match preceding the first of
*PatternName*.
+	 * Discards every partial match that started before the first event of emitted match mapped
to *PatternName*.
 	 *
 	 * @param patternName the pattern name to skip to
 	 * @return the created AfterMatchSkipStrategy
@@ -48,7 +48,7 @@ public static SkipToFirstStrategy skipToFirst(String patternName) {
 	}
 
 	/**
-	 * Discards every partial match that contains event of the match preceding the last of *PatternName*.
+	 * Discards every partial match that started before the last event of emitted match mapped
to *PatternName*.
 	 *
 	 * @param patternName the pattern name to skip to
 	 * @return the created AfterMatchSkipStrategy
@@ -58,7 +58,7 @@ public static SkipToLastStrategy skipToLast(String patternName) {
 	}
 
 	/**
-	 * Discards every partial match that contains event of the match.
+	 * Discards every partial match that started before emitted match ended.
 	 *
 	 * @return the created AfterMatchSkipStrategy
 	 */
@@ -66,6 +66,15 @@ public static SkipPastLastStrategy skipPastLastEvent() {
 		return SkipPastLastStrategy.INSTANCE;
 	}
 
+	/**
+	 * Discards every partial match that started with the same event, emitted match was started.
+	 *
+	 * @return the created AfterMatchSkipStrategy
+	 */
+	public static AfterMatchSkipStrategy skipToNext() {
+		return SkipToNextStrategy.INSTANCE;
+	}
+
 	/**
 	 * Every possible match will be emitted.
 	 *
@@ -149,6 +158,22 @@ static EventId max(EventId o1, EventId o2) {
 		}
 	}
 
+	static EventId min(EventId o1, EventId o2) {
+		if (o2 == null) {
+			return o1;
+		}
+
+		if (o1 == null) {
+			return o2;
+		}
+
+		if (o1.compareTo(o2) <= 0) {
+			return o1;
+		} else {
+			return o2;
+		}
+	}
+
 	/** Forbid further extending. */
 	AfterMatchSkipStrategy() {
 	}
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipPastLastStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipPastLastStrategy.java
index 952d91acb92..c8441e54fa1 100644
--- a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipPastLastStrategy.java
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipPastLastStrategy.java
@@ -25,9 +25,9 @@
 import java.util.Map;
 
 /**
- * Discards every partial match that contains event of the match.
+ * Discards every partial match that started before emitted match ended.
  */
-public class SkipPastLastStrategy extends AfterMatchSkipStrategy {
+public final class SkipPastLastStrategy extends SkipRelativeToWholeMatchStrategy {
 
 	public static final SkipPastLastStrategy INSTANCE = new SkipPastLastStrategy();
 
@@ -36,16 +36,6 @@
 	private SkipPastLastStrategy() {
 	}
 
-	@Override
-	public boolean isSkipStrategy() {
-		return true;
-	}
-
-	@Override
-	protected boolean shouldPrune(EventId startEventID, EventId pruningId) {
-		return startEventID != null && startEventID.compareTo(pruningId) <= 0;
-	}
-
 	@Override
 	protected EventId getPruningId(final Collection<Map<String, List<EventId>>>
match) {
 		EventId pruningId = null;
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipRelativeToWholeMatchStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipRelativeToWholeMatchStrategy.java
new file mode 100644
index 00000000000..00bce97f38f
--- /dev/null
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipRelativeToWholeMatchStrategy.java
@@ -0,0 +1,35 @@
+/*
+ * 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.aftermatch;
+
+import org.apache.flink.cep.nfa.sharedbuffer.EventId;
+
+abstract class SkipRelativeToWholeMatchStrategy extends AfterMatchSkipStrategy {
+	private static final long serialVersionUID = -3214720554878479037L;
+
+	@Override
+	public final boolean isSkipStrategy() {
+		return true;
+	}
+
+	@Override
+	protected final boolean shouldPrune(EventId startEventID, EventId pruningId) {
+		return startEventID != null && startEventID.compareTo(pruningId) <= 0;
+	}
+}
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToFirstStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToFirstStrategy.java
index e8befebe5fc..6425a13e36e 100644
--- a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToFirstStrategy.java
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToFirstStrategy.java
@@ -19,7 +19,7 @@
 package org.apache.flink.cep.nfa.aftermatch;
 
 /**
- * Discards every partial match that contains event of the match preceding the first of *PatternName*.
+ * Discards every partial match that started before the first event of emitted match mapped
to *PatternName*.
  */
 public final class SkipToFirstStrategy extends SkipToElementStrategy {
 	private static final long serialVersionUID = 7127107527654629026L;
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToLastStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToLastStrategy.java
index 3c33bd13f62..ec8ea549d0e 100644
--- a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToLastStrategy.java
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToLastStrategy.java
@@ -19,7 +19,7 @@
 package org.apache.flink.cep.nfa.aftermatch;
 
 /**
- * Discards every partial match that contains event of the match preceding the last of *PatternName*.
+ * Discards every partial match that started before the last event of emitted match mapped
to *PatternName*.
  */
 public final class SkipToLastStrategy extends SkipToElementStrategy {
 	private static final long serialVersionUID = 7585116990619594531L;
diff --git a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToNextStrategy.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToNextStrategy.java
new file mode 100644
index 00000000000..5d7b354bd43
--- /dev/null
+++ b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/aftermatch/SkipToNextStrategy.java
@@ -0,0 +1,55 @@
+/*
+ * 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.aftermatch;
+
+import org.apache.flink.cep.nfa.sharedbuffer.EventId;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Discards every partial match that started with the same event, emitted match was started.
+ */
+public final class SkipToNextStrategy extends SkipRelativeToWholeMatchStrategy {
+
+	public static final SkipToNextStrategy INSTANCE = new SkipToNextStrategy();
+
+	private static final long serialVersionUID = -6490314998588752621L;
+
+	private SkipToNextStrategy() {
+	}
+
+	@Override
+	protected EventId getPruningId(final Collection<Map<String, List<EventId>>>
match) {
+		EventId pruningId = null;
+		for (Map<String, List<EventId>> resultMap : match) {
+			for (List<EventId> eventList : resultMap.values()) {
+				pruningId = min(pruningId, eventList.get(0));
+			}
+		}
+
+		return pruningId;
+	}
+
+	@Override
+	public String toString() {
+		return "SkipToNextStrategy{}";
+	}
+}
diff --git a/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/AfterMatchSkipITCase.java
b/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/AfterMatchSkipITCase.java
index 6681090d8b2..d42839e3071 100644
--- a/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/AfterMatchSkipITCase.java
+++ b/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/AfterMatchSkipITCase.java
@@ -45,7 +45,7 @@
 public class AfterMatchSkipITCase extends TestLogger{
 
 	@Test
-	public void testSkipToNext() throws Exception {
+	public void testNoSkip() throws Exception {
 		List<StreamRecord<Event>> streamEvents = new ArrayList<>();
 
 		Event a1 = new Event(1, "a", 0.0);
@@ -83,6 +83,121 @@ public boolean filter(Event value) throws Exception {
 		));
 	}
 
+	@Test
+	public void testNoSkipWithFollowedByAny() throws Exception {
+		List<List<Event>> resultingPatterns = TwoVariablesFollowedByAny.compute(AfterMatchSkipStrategy.noSkip());
+
+		compareMaps(resultingPatterns, Lists.newArrayList(
+			Lists.newArrayList(TwoVariablesFollowedByAny.a1, TwoVariablesFollowedByAny.b1),
+			Lists.newArrayList(TwoVariablesFollowedByAny.a1, TwoVariablesFollowedByAny.b2),
+			Lists.newArrayList(TwoVariablesFollowedByAny.a2, TwoVariablesFollowedByAny.b2)
+		));
+	}
+
+	@Test
+	public void testSkipToNextWithFollowedByAny() throws Exception {
+		List<List<Event>> resultingPatterns = TwoVariablesFollowedByAny.compute(AfterMatchSkipStrategy.skipToNext());
+
+		compareMaps(resultingPatterns, Lists.newArrayList(
+			Lists.newArrayList(TwoVariablesFollowedByAny.a1, TwoVariablesFollowedByAny.b1),
+			Lists.newArrayList(TwoVariablesFollowedByAny.a2, TwoVariablesFollowedByAny.b2)
+		));
+	}
+
+	static class TwoVariablesFollowedByAny {
+
+		static Event a1 = new Event(1, "a", 0.0);
+		static Event b1 = new Event(2, "b", 0.0);
+		static Event a2 = new Event(4, "a", 0.0);
+		static Event b2 = new Event(5, "b", 0.0);
+
+		private static List<List<Event>> compute(AfterMatchSkipStrategy skipStrategy)
throws Exception {
+			List<StreamRecord<Event>> streamEvents = new ArrayList<>();
+
+			streamEvents.add(new StreamRecord<>(a1));
+			streamEvents.add(new StreamRecord<>(b1));
+			streamEvents.add(new StreamRecord<>(a2));
+			streamEvents.add(new StreamRecord<>(b2));
+
+			Pattern<Event, ?> pattern = Pattern.<Event>begin("start")
+				.where(new SimpleCondition<Event>() {
+
+					@Override
+					public boolean filter(Event value) throws Exception {
+						return value.getName().equals("a");
+					}
+				}).followedByAny("end")
+				.where(new SimpleCondition<Event>() {
+
+					@Override
+					public boolean filter(Event value) throws Exception {
+						return value.getName().equals("b");
+					}
+				});
+
+			NFA<Event> nfa = compile(pattern, false);
+
+			return feedNFA(streamEvents, nfa, skipStrategy);
+		}
+	}
+
+	@Test
+	public void testNoSkipWithQuantifierAtTheEnd() throws Exception {
+		List<List<Event>> resultingPatterns = QuantifierAtEndOfPattern.compute(AfterMatchSkipStrategy.noSkip());
+
+		compareMaps(resultingPatterns, Lists.newArrayList(
+			Lists.newArrayList(QuantifierAtEndOfPattern.a1, QuantifierAtEndOfPattern.b1,  QuantifierAtEndOfPattern.b2,
 QuantifierAtEndOfPattern.b3),
+			Lists.newArrayList(QuantifierAtEndOfPattern.a1, QuantifierAtEndOfPattern.b1,  QuantifierAtEndOfPattern.b2),
+			Lists.newArrayList(QuantifierAtEndOfPattern.a1, QuantifierAtEndOfPattern.b1)
+		));
+	}
+
+	@Test
+	public void testSkipToNextWithQuantifierAtTheEnd() throws Exception {
+		List<List<Event>> resultingPatterns = QuantifierAtEndOfPattern.compute(AfterMatchSkipStrategy.skipToNext());
+
+		compareMaps(resultingPatterns, Lists.<List<Event>>newArrayList(
+			Lists.newArrayList(QuantifierAtEndOfPattern.a1, QuantifierAtEndOfPattern.b1)
+		));
+	}
+
+	static class QuantifierAtEndOfPattern {
+
+		static Event a1 = new Event(1, "a", 0.0);
+		static Event b1 = new Event(2, "b", 0.0);
+		static Event b2 = new Event(4, "b", 0.0);
+		static Event b3 = new Event(5, "b", 0.0);
+
+		private static List<List<Event>> compute(AfterMatchSkipStrategy skipStrategy)
throws Exception {
+			List<StreamRecord<Event>> streamEvents = new ArrayList<>();
+
+			streamEvents.add(new StreamRecord<>(a1));
+			streamEvents.add(new StreamRecord<>(b1));
+			streamEvents.add(new StreamRecord<>(b2));
+			streamEvents.add(new StreamRecord<>(b3));
+
+			Pattern<Event, ?> pattern = Pattern.<Event>begin("start")
+				.where(new SimpleCondition<Event>() {
+
+					@Override
+					public boolean filter(Event value) throws Exception {
+						return value.getName().equals("a");
+					}
+				}).next("end")
+				.where(new SimpleCondition<Event>() {
+
+					@Override
+					public boolean filter(Event value) throws Exception {
+						return value.getName().equals("b");
+					}
+				}).oneOrMore();
+
+			NFA<Event> nfa = compile(pattern, false);
+
+			return feedNFA(streamEvents, nfa, skipStrategy);
+		}
+	}
+
 	@Test
 	public void testSkipPastLast() throws Exception {
 		List<StreamRecord<Event>> streamEvents = new ArrayList<>();


 

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> Add skip to next strategy
> -------------------------
>
>                 Key: FLINK-10414
>                 URL: https://issues.apache.org/jira/browse/FLINK-10414
>             Project: Flink
>          Issue Type: Improvement
>          Components: CEP
>            Reporter: Dawid Wysakowicz
>            Assignee: Dawid Wysakowicz
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.7.0
>
>
> Add skip to next strategy, that should discard all partial matches that started with
the same element as found match.



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