Flink table api

Depending on the requirements of a table program, it might be necessary to adjust certain parameters for optimization. For example, unbounded streaming programs may need to ensure that the required state size is capped see streaming concepts. In every table environment, the TableConfig offers options for configuring the current session.

For common or important configuration options, the TableConfig provides getters and setters methods with detailed inline documentation. For more advanced configuration, users can directly access the underlying key-value map. Attention Because options are read at different point in time when performing operations, it is recommended to set configuration options early after instantiating a table environment. Attention Currently, key-value options are only supported for the Blink planner.

The following options can be used to adjust the behavior of the query optimizer to get a better execution plan. Flink Operations Playground. Local Setup Running Flink on Windows. Overview Batch Examples. Programming Model Distributed Runtime Glossary. Streaming Aggregation. Overview Custom Serializers. Pick Docs Version v1. Want to contribute translation? Mainly for testing. A comma-separated list of operator names, each name represents a kind of disabled operator.

By default no operator is disabled. The maximum latency can be used for MiniBatch to buffer input records. MiniBatch is an optimization to buffer input records to reduce state access.

MiniBatch is triggered with the allowed latency interval and when the maximum number of buffered records reached. NOTE: If table. Specifies whether to enable MiniBatch optimization. This is disabled by default.

To enable this, users should set this config to true. NOTE: If mini-batch is enabled, 'table. The maximum number of input records can be buffered for MiniBatch.

If table.

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Sets default parallelism for all operators such as aggregate, join, filter to run with parallel instances. This config has a higher priority than parallelism of StreamExecutionEnvironment actually, this config overrides the parallelism of StreamExecutionEnvironment. A value of -1 indicates that no default parallelism is set, then it will fallback to use the parallelism of StreamExecutionEnvironment.

Sets exec shuffle mode. Only batch or pipelined can be set.Please keep the discussion on the mailing list rather than commenting on the wiki wiki discussions get unwieldy fast. So far, only projection, selection, and union are supported operations on streaming tables.

This FLIP proposes to add support for different types of aggregations on top of streaming tables. In particular, we seek to support:. Group-window aggregates, i. A time or row-count window is required to bound the infinite input stream into a finite group.

Row-window aggregates, i. Since time-windowed aggregates will be the first operation that require the definition of time, this FLIP does also discuss how the Table API handles time characteristics, timestamps, and watermarks. The feature will extend the Table API. We propose the following methods:. Group-windows are evaluated once per group and defined using the window w: Window method.

The Window parameter defines the type and parameters of the window to compute. The window method can be applied on a Table yielding a non-keyed DataStream. Tumbling Event-time window:. Tumbling Processing-time window:. Tumbling Row-count window:. Defines the length the window, either by time or row count. Assigns an alias for the window that the following select clause can refer to in order to access window properties such as window start or end time. Sliding Event-time window:.

Sliding Processing-time window:. Sliding Row-count window:. Defines how frequent a new window is created, either by time or row count. The creation interval must be of the same type as the window length. Session Event-time window:.

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Session Processing-time window:. Assigns an alias for the table that the following select clause can refer to in order to access window properties such as window start or end time.

Row-window aggregates are evaluated for each row and a row window defines for each row the range of preceding and succeeding rows over which an aggregation function is evaluated. If more than one aggregation function is evaluated for a result row, each aggregation function can be evaluated over a separate row window.

The rw parameter defines one or more row windows. Each row window must have an alias assigned.

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Aggregates in the select method must refer to a RowWindow by providing an alias in the over clause. The rowWindow method can be applied to a Table yielding a non-keyed row-window aggregation or to a GroupedTable resulting in a keyed row-window aggregation.

Event-time row-windows process rows with increasing timestamps i. Hence, only ordered processing will guarantee consistent results. Similar to the group window definition WindowRowWindow is not an interface that users can implement, but rather a collection of built-in API objects that are internally translated into efficient DataStream operators.

There are many different ways how RowWindows can be defined, e.

Configuration

The first version of row-window aggregates will not support multiple RowWindow definitions. The following RowWindow definitions will be initially provided.With the release of Apache Flink 1. Flink offers various APIs for accessing streaming data. For this example, we use our example data generator — Planestream. The generated ADS-B data has the property of having sparse messages where not every message has every key in it. We need to write a simple data processor to ensure we have high-quality data for some downstream sink.

Our processor needs to ignore messages without the altitude key, as well as shorten the message to only the specific keys we are interested in. We need a simple way to read data from a Kafka topic, ensure that a key is present, and then write a subset of fields into another Kafka topic. There are some core components we use to access and process the data. This should help you quickly absorb the core meat of the program and differentiate it from the basic scaffolding of a Flink program.

To get the data we need to configure a source. This is always running against the stream, not a singleton point in time query. Now we have a result table object that is our filtered data. We need to write that to a Kafka topic. We pass it the topic to write to, properties, and a partition object.

The partition object is simply the type of partitioning to use when writing the data to Kafka. Finally, we call the writeToSink method on the result specifying the sink to write to. At a high level, the anatomy of a Flink program that uses the Flink table API is detailed here for 1. You can find the entire source of the project on Github. Feel free to fork it and experiment on your own. Be sure to check out the docs here 1. As always if you have questions feel free to ping us at support eventador.

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Log In Get Started. Kenny Gorman. Leave a Reply Cancel reply Your email address will not be published.The Table API is a language-integrated query API for Scala and Java that allows the composition of queries from relational operators such as selection, filter, and join in a very intuitive way.

Queries specified in either interface have the same semantics and specify the same result regardless whether the input is a batch input DataSet or a stream input DataStream. For instance, you can extract patterns from a DataStream using the CEP library and later use the Table API to analyze the patterns, or you might scan, filter, and aggregate a batch table using a SQL query before running a Gelly graph algorithm on the preprocessed data.

Starting from Flink 1. Planners are responsible for translating relational operators into an executable, optimized Flink job. Both of the planners come with different optimization rules and runtime classes. They may also differ in the set of supported features. Attention For production use cases, we recommend the old planner that was present before Flink 1.

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See the common API page for more information about how to switch between the old and new Blink planner in table programs. Internally, parts of the table ecosystem are implemented in Scala. Therefore, please make sure to add the following dependency for both batch and streaming applications:. If you want to implement a custom format for interacting with Kafka or a set of user-defined functionsthe following dependency is sufficient and can be used for JAR files for the SQL Client:.

Back to top. Flink Operations Playground. Local Setup Running Flink on Windows.

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Overview Batch Examples. Programming Model Distributed Runtime Glossary. Streaming Aggregation. Overview Custom Serializers. Pick Docs Version v1.It supports all features of the HadoopOffice library, such as encryption, signing, linked workbooks, templates or low footprint mode.

The Table Source is available for Scala 2. Example for the file testsimple. This file has dates as Excel standard in US format and decimals stored in German format e. It skips the first line of the first sheet in the Excel, because it is the header line and does not contain data. The following example describes how a result from a query "testSimpleResult" of a FlinkTable is stored as a file in new Excel Format see mimetype in Hadoop File Format. It writes the field names of the Flink Table as the first row of the Excel useHeader: true.

All data is written in the Sheet "Sheet 1". Skip to content.

flink table api

The order of the field commands describe which column of the Excel is meant, e. Note that in most cases - even for Excels written using Excel for Non-US countries you may want to choose US, because this is the Excel default format. However, if your dates are Excel strings you may need to select other formats. Default: Locale. Those can vary from country to country.

For instance, in Germany the comma is the equivalent to the US dot. Default: Locale of the system dateTimeFormat as of 1. You can define any Locale here to read timestamps. However using SimpleDateFormat you can define any date format pattern.

Default: null this means the pattern defined in java. Timestamp will be used. US decimalFormat: Format of decimals. Pages You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window.With the Table API, you can apply relational operators such as selection, aggregation, and joins on Table s.

See linking with it for cluster execution here. TableEnvironment s have an internal table catalog to which tables can be registered with a unique name. After registration, a table can be accessed from the TableEnvironment by its name.

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An external table is registered in a TableEnvironment using a TableSource as follows:. All sources that come with the flink-table dependency can be directly used by your Table programs. For all other table sources, you have to add the respective dependency in addition to the flink-table dependency. The CsvTableSource is already included in flink-table without additional dependecies.

The central concept of the Table API is a Table which represents a table with relational schema or relation. A Table is always bound to a specific TableEnvironment. It is not possible to combine Tables of different TableEnvironments. Note: The only operations currently supported on streaming Tables are selection, projection, and union. The following example shows:. With Java, expressions must be specified by Strings. The embedded expression DSL is not supported.

Please refer to the Javadoc for a full list of supported operations and a description of the expression syntax. The Table API is enabled by importing org. The expression DSL uses Scala symbols to refer to field names and code generation to transform expressions to efficient runtime code.

Notice, how the field names of a Table can be changed with as or specified with toTable when converting a DataSet to a Table. In addition, the example shows how to use Strings to specify relational expressions.

Creating a Table from a DataStream works in a similar way. Please refer to the Scaladoc for a full list of supported operations and a description of the expression syntax.

Continuous Queries on Dynamic Tables

Back to top. The Table API features a domain-specific language to execute language-integrated queries on structured data in Scala and Java. This section gives a brief overview of the available operators. You can find more details of operators in the Javadoc. Groups the rows on the grouping keys, with a following aggregation operator to aggregate rows group-wise. Joins two tables. Both tables must have distinct field names and at least one equality join predicate must be defined through join operator or using a where or filter operator.

Both tables must have distinct field names and at least one equality join predicate must be defined. Unions two tables with duplicate records removed. Both tables must have identical field types. Unions two tables.

Intersect returns records that exist in both tables. If a record is present one or both tables more than once, it is returned just once, i. IntersectAll returns records that exist in both tables.

flink table api

If a record is present in both tables more than once, it is returned as many times as it is present in both tables, i. Minus returns records from the left table that do not exist in the right table.More and more companies are adopting stream processing and are migrating existing batch applications to streaming or implementing streaming solutions for new use cases.

Many of those applications focus on analyzing streaming data. The data streams that are analyzed come from a wide variety of sources such as database transactions, clicks, sensor measurements, or IoT devices. Apache Flink is very well suited to power streaming analytics applications because it provides support for event-time semantics, stateful exactly-once processing, and achieves high throughput and low latency at the same time.

Due to these features, Flink is able to compute exact and deterministic results from high-volume input streams in near real-time while providing exactly-once semantics in case of failures. Among other features, it offers highly customizable windowing logic, different state primitives with varying performance characteristics, hooks to register and react on timers, and tooling for efficient asynchronous requests to external systems.

On the other hand, many stream analytics applications follow similar patterns and do not require the level of expressiveness as provided by the DataStream API. They could be expressed in a more natural and concise way using a domain specific language. As we all know, SQL is the de-facto standard for data analytics. For streaming analytics, SQL would enable a larger pool of people to specify applications on data streams in less time.

flink table api

However, no open source stream processor offers decent SQL support yet. So being able to process and analyze data streams with SQL makes stream processing technology available to many more users. However, SQL and the relational data model and algebra were not designed with streaming data in mind. Relations are multi- sets and not infinite sequences of tuples. When executing a SQL query, conventional database systems and query engines read and process a data set, which is completely available, and produce a fixed sized result.

In contrast, data streams continuously provide new records such that data arrives over time. That being said, processing streams with SQL is not impossible. Some relational database systems feature eager maintenance of materialized views, which is similar to evaluating SQL queries on streams of data.

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A materialized view is defined as a SQL query just like a regular virtual view. However, the result of the query is actually stored or materialized in memory or on disk such that the view does not need to be computed on-the-fly when it is queried. In order to prevent that a materialized view becomes stale, the database system needs to update the view whenever its base relations the tables referenced in its definition query are modified.

Since version 1.