[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16639833#comment-16639833
]
ASF GitHub Bot commented on FLINK-10470:
dawidwys closed pull request #6781: [FLINK-10470] Add method to check if
pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781
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/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
index 8f49f68fe41..ed2ff2e7e59 100644
---
a/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
+++
b/flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
@@ -40,8 +40,13 @@
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
+import java.util.HashSet;
import java.util.List;
import java.util.Map;
+import java.util.Set;
+import java.util.Stack;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
/**
* Compiler class containing methods to compile a {@link Pattern} into a
{@link NFA} or a
@@ -74,6 +79,44 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().orElseThrow(
+ () -> new IllegalStateException("Compiler produced no
start state. It is a bug. File a jira."));
+
+ Set> visitedStates = new HashSet<>();
+ final Stack> statesToCheck = new Stack<>();
+ statesToCheck.push(startState);
+ while (!statesToCheck.isEmpty()) {
+ final State currentState = statesToCheck.pop();
+ if (visitedStates.contains(currentState)) {
+ continue;
+ } else {
+ visitedStates.add(currentState);
+ }
+
+ for (StateTransition transition :
currentState.getStateTransitions()) {
+ if (transition.getAction() ==
StateTransitionAction.PROCEED) {
+ if
(transition.getTargetState().isFinal()) {
+ return true;
+ } else {
+
statesToCheck.push(transition.getTargetState());
+ }
+ }
+ }
+ }
+
+ return false;
+ }
+
/**
* Converts a {@link Pattern} into graph of {@link State}. It enables
sharing of
* compilation state across methods.
diff --git
a/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/compiler/NFACompilerTest.java
b/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/compiler/NFACompilerTest.java
index f39b17483cd..821da031c6d 100644
---
a/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/compiler/NFACompilerTest.java
+++
b/flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/compiler/NFACompilerTest.java
@@ -44,7 +44,9 @@
import java.util.Set;
import static org.apache.flink.cep.utils.NFAUtils.compile;
+import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;
/**
@@ -226,4 +228,14 @@ public boolean filter(Event value) throws Exception {
return transitions;
}
+ @Test
+ public void testCheckingEmptyMatches() {
+
assertThat(NFACompiler.canProduceEmptyMatches(Pattern.begin("a").optional()),
is(true));
+
assertThat(NFACompiler.canProduceEmptyMatches(Pattern.begin("a").oneOrMore().optional()),
is(true));
+
assertThat(NFACompiler.canProduceEmptyMatches(Pattern.begin("a").oneOrMore().optional().next("b").optional()),
is(true));
+
+
a
[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16638073#comment-16638073
]
ASF GitHub Bot commented on FLINK-10470:
pnowojski commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r222622968
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
Review comment:
But that's the convention: you `checkState`, `checkArgument`, throw
`IllegalStateException` or `IllegalArgumentException` to cover for bugs in the
code - the situations/class states that should never happen.
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16638074#comment-16638074
]
ASF GitHub Bot commented on FLINK-10470:
pnowojski commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r222623342
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
+
+ final Stack> statesToCheck = new Stack<>();
+ statesToCheck.push(startState);
+ while (!statesToCheck.isEmpty()) {
+ final State currentState = statesToCheck.pop();
+ for (StateTransition transition :
currentState.getStateTransitions()) {
+ if (transition.getAction() ==
StateTransitionAction.PROCEED) {
+ if
(transition.getTargetState().isFinal()) {
+ return true;
+ } else {
+
statesToCheck.push(transition.getTargetState());
Review comment:
It would be better to at least throw `IllegalStateException` instead of
looping forever in case of some bug or if someone will refactor/add new feature
to the compiler.
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
--
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[ https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16637919#comment-16637919 ] ASF GitHub Bot commented on FLINK-10470: dawidwys commented on issue #6781: [FLINK-10470] Add method to check if pattern can produce empty matches URL: https://github.com/apache/flink/pull/6781#issuecomment-426924231 @pnowojski could you have another look? This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org > Add method to check if pattern can produce empty matches > > > Key: FLINK-10470 > URL: https://issues.apache.org/jira/browse/FLINK-10470 > Project: Flink > Issue Type: Sub-task > Components: CEP >Reporter: Dawid Wysakowicz >Assignee: Dawid Wysakowicz >Priority: Major > Labels: pull-request-available > > There is couple of inconsistencies how CEP library handles greedy and > reluctant operators at the beginning at end of pattern. This results in > subtle problems how empty matches should be generated for patterns like e.g. > A? or A*?, where one is greedy and the other one is reluctant. In order to > provide first version of MATCH_RECOGNIZE function we should have a > possibility to disable patterns which can produce empty matches. -- This message was sent by Atlassian JIRA (v7.6.3#76005)
[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16634186#comment-16634186
]
ASF GitHub Bot commented on FLINK-10470:
dawidwys commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r221640962
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
Review comment:
Ok, will change it. In general though I am always torn in this situations,
cause that would mean we have a bug in our compiler, so it is actually not an
`IllegalState`
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
--
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16634147#comment-16634147
]
ASF GitHub Bot commented on FLINK-10470:
dawidwys commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r221640962
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
Review comment:
Ok, will change it. In general though I am always torn in this situations,
cause that would mean we have a bug in our compiler.
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
--
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16634145#comment-16634145
]
ASF GitHub Bot commented on FLINK-10470:
dawidwys commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r221640010
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
+
+ final Stack> statesToCheck = new Stack<>();
+ statesToCheck.push(startState);
+ while (!statesToCheck.isEmpty()) {
+ final State currentState = statesToCheck.pop();
+ for (StateTransition transition :
currentState.getStateTransitions()) {
+ if (transition.getAction() ==
StateTransitionAction.PROCEED) {
+ if
(transition.getTargetState().isFinal()) {
+ return true;
+ } else {
+
statesToCheck.push(transition.getTargetState());
Review comment:
Theoretically yes, practically compiler won't produce such graph as of now.
Do you think I should be defensive though?
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
--
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16633875#comment-16633875
]
ASF GitHub Bot commented on FLINK-10470:
pnowojski commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r221576741
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
Review comment:
nit: `orElseThrow(IllegalStateException::new)` (or sth like this, I'm not
sure what's the correct syntax) instead of `get()`?
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
--
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[
https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16633874#comment-16633874
]
ASF GitHub Bot commented on FLINK-10470:
pnowojski commented on a change in pull request #6781: [FLINK-10470] Add method
to check if pattern can produce empty matches
URL: https://github.com/apache/flink/pull/6781#discussion_r221577049
##
File path:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
##
@@ -74,6 +77,36 @@
}
}
+ /**
+* Verifies if the provided pattern can possibly generate empty match.
Example of patterns that can possibly
+* generate empty matches are: A*, A?, A* B? etc.
+*
+* @param pattern pattern to check
+* @return true if empty match could potentially match the pattern,
false otherwise
+*/
+ public static boolean canProduceEmptyMatches(final Pattern
pattern) {
+ NFAFactoryCompiler compiler = new
NFAFactoryCompiler<>(checkNotNull(pattern));
+ compiler.compileFactory();
+ State startState =
compiler.getStates().stream().filter(State::isStart).findFirst().get();
+
+ final Stack> statesToCheck = new Stack<>();
+ statesToCheck.push(startState);
+ while (!statesToCheck.isEmpty()) {
+ final State currentState = statesToCheck.pop();
+ for (StateTransition transition :
currentState.getStateTransitions()) {
+ if (transition.getAction() ==
StateTransitionAction.PROCEED) {
+ if
(transition.getTargetState().isFinal()) {
+ return true;
+ } else {
+
statesToCheck.push(transition.getTargetState());
Review comment:
Can we loop here forever if `PROCEED` takes us to already visited node?
Shouldn't we check for already visited states?
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> Add method to check if pattern can produce empty matches
>
>
> Key: FLINK-10470
> URL: https://issues.apache.org/jira/browse/FLINK-10470
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
>Reporter: Dawid Wysakowicz
>Assignee: Dawid Wysakowicz
>Priority: Major
> Labels: pull-request-available
>
> There is couple of inconsistencies how CEP library handles greedy and
> reluctant operators at the beginning at end of pattern. This results in
> subtle problems how empty matches should be generated for patterns like e.g.
> A? or A*?, where one is greedy and the other one is reluctant. In order to
> provide first version of MATCH_RECOGNIZE function we should have a
> possibility to disable patterns which can produce empty matches.
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[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[ https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16633854#comment-16633854 ] ASF GitHub Bot commented on FLINK-10470: dawidwys commented on issue #6781: [FLINK-10470] Add method to check if pattern can produce empty matches URL: https://github.com/apache/flink/pull/6781#issuecomment-425868325 cc @kl0u @pnowojski This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org > Add method to check if pattern can produce empty matches > > > Key: FLINK-10470 > URL: https://issues.apache.org/jira/browse/FLINK-10470 > Project: Flink > Issue Type: Sub-task > Components: CEP >Reporter: Dawid Wysakowicz >Assignee: Dawid Wysakowicz >Priority: Major > Labels: pull-request-available > > There is couple of inconsistencies how CEP library handles greedy and > reluctant operators at the beginning at end of pattern. This results in > subtle problems how empty matches should be generated for patterns like e.g. > A? or A*?, where one is greedy and the other one is reluctant. In order to > provide first version of MATCH_RECOGNIZE function we should have a > possibility to disable patterns which can produce empty matches. -- This message was sent by Atlassian JIRA (v7.6.3#76005)
[jira] [Commented] (FLINK-10470) Add method to check if pattern can produce empty matches
[ https://issues.apache.org/jira/browse/FLINK-10470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16633712#comment-16633712 ] ASF GitHub Bot commented on FLINK-10470: dawidwys opened a new pull request #6781: [FLINK-10470] Add method to check if pattern can produce empty matches URL: https://github.com/apache/flink/pull/6781 ## What is the purpose of the change This change introduces a method that allows checking if a Pattern can produce empty matches. It is needed to disable such patterns in MATCH_RECOGNIZE, until we are able to provide a full support of empty matches in CEP (with proper support of reluctant and greedy) ## Does this pull request potentially affect one of the following parts: - Dependencies (does it add or upgrade a dependency): (yes / **no**) - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (yes / **no**) - The serializers: (yes / **no** / don't know) - The runtime per-record code paths (performance sensitive): (yes / **no** / don't know) - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes / **no** / don't know) - The S3 file system connector: (yes / **no** / don't know) ## Documentation - Does this pull request introduce a new feature? (yes / **no**) - If yes, how is the feature documented? (**not applicable** / docs / JavaDocs / not documented) This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org > Add method to check if pattern can produce empty matches > > > Key: FLINK-10470 > URL: https://issues.apache.org/jira/browse/FLINK-10470 > Project: Flink > Issue Type: Sub-task > Components: CEP >Reporter: Dawid Wysakowicz >Assignee: Dawid Wysakowicz >Priority: Major > Labels: pull-request-available > > There is couple of inconsistencies how CEP library handles greedy and > reluctant operators at the beginning at end of pattern. This results in > subtle problems how empty matches should be generated for patterns like e.g. > A? or A*?, where one is greedy and the other one is reluctant. In order to > provide first version of MATCH_RECOGNIZE function we should have a > possibility to disable patterns which can produce empty matches. -- This message was sent by Atlassian JIRA (v7.6.3#76005)
