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https://issues.apache.org/jira/browse/FLINK-10625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16688347#comment-16688347
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ASF GitHub Bot commented on FLINK-10625:
----------------------------------------
alpinegizmo commented on a change in pull request #7070: [FLINK-10625]
Documentation for MATCH_RECOGNIZE clause
URL: https://github.com/apache/flink/pull/7070#discussion_r233889947
##########
File path: docs/dev/table/streaming/match_recognize.md
##########
@@ -0,0 +1,843 @@
+---
+title: 'Detecting Patterns in Tables'
+nav-parent_id: streaming_tableapi
+nav-title: 'Detecting Patterns'
+nav-pos: 5
+is_beta: true
+---
+<!--
+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.
+-->
+
+It is a common use-case to search for a set of event patterns, especially in
case of data streams. Flink
+comes with a [complex event processing (CEP) library]({{ site.baseurl
}}/dev/libs/cep.html) which allows for pattern detection in event streams.
Furthermore, Flink's
+SQL API provides a relational way of expressing queries with a large set of
built-in functions and rule-based optimizations that can be used out of the box.
+
+In December 2016, the International Organization for Standardization (ISO)
released a new version of the SQL standard which includes _Row Pattern
Recognition in SQL_ ([ISO/IEC TR
19075-5:2016](https://standards.iso.org/ittf/PubliclyAvailableStandards/c065143_ISO_IEC_TR_19075-5_2016.zip)).
It allows Flink to consolidate CEP and SQL API using the `MATCH_RECOGNIZE`
clause for complex event processing in SQL.
+
+A `MATCH_RECOGNIZE` clause enables the following tasks:
+* Logically partition and order the data that is used with `PARTITION BY` and
`ORDER BY` clauses.
+* Define patterns of rows to seek using the `PATTERN` clause. These patterns
use a syntax similar to that of regular expressions.
+* Specify logical conditions required to map a row to a row pattern variable
in the `DEFINE` clause.
+* Define measures, which are expressions usable in other parts of the SQL
query, in the `MEASURES` clause.
+
+The following example illustates the syntax for basic pattern recognition:
+
+{% highlight sql %}
+SELECT T.aid, T.bid, T.cid
+FROM MyTable
+MATCH_RECOGNIZE (
+ PARTITION BY userid
+ ORDER BY proctime
+ MEASURES
+ A.id AS aid,
+ B.id AS bid,
+ C.id AS cid
+ PATTERN (A B C)
+ DEFINE
+ A AS name = 'a',
+ B AS name = 'b',
+ C AS name = 'c'
+) AS T
+{% endhighlight %}
+
+This page will explain each keyword in more detail and will illustrate more
complex examples.
+
+<span class="label label-danger">Attention</span> The `MATCH_RECOGNIZE` clause
implementation in Flink is just a subset of the bigger pattern recognition
standard. Only the features that are documented in the following sections are
supported so far. Since the development is still in an early phase, please also
take a look at the [known limitations](#known-limitations).
Review comment:
```suggestion
<span class="label label-danger">Attention</span> Flink's implementation of
the `MATCH_RECOGNIZE` clause is a subset of the full standard. Only those
features documented in the following sections are supported. Since the
development is still in an early phase, please also take a look at the [known
limitations](#known-limitations).
```
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> Add MATCH_RECOGNIZE documentation
> ---------------------------------
>
> Key: FLINK-10625
> URL: https://issues.apache.org/jira/browse/FLINK-10625
> Project: Flink
> Issue Type: Sub-task
> Components: Documentation, Table API & SQL
> Affects Versions: 1.7.0
> Reporter: Till Rohrmann
> Assignee: Dawid Wysakowicz
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.7.0
>
>
> The newly added {{MATCH_RECOGNIZE}} functionality needs to be documented.
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