anishshri-db commented on code in PR #43920: URL: https://github.com/apache/spark/pull/43920#discussion_r1402768924
########## docs/structured-streaming-state-data-source.md: ########## @@ -0,0 +1,248 @@ +--- +layout: global +displayTitle: State data source (Experimental) Guide in Structured Streaming +title: State data source (Experimental) Guide in Structured Streaming +license: | + 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. +--- + +State data source Guide in Structured Streaming (Experimental) + +## Overview + +State data source provides functionality to manipulate the state from the checkpoint. + +As of Spark 4.0, state data source provides the read functionality with a batch query. Additional functionalities including write is on the future roadmap. + +NOTE: This data source is under experimental - source options and the behavior (output) might be subject to change. + +## Reading state key-values from the checkpoint + +State data source enables reading key-value pairs from the state in the checkpoint, via running a separate batch query. +Users can leverage the functionality to cover two major use cases described below: + +* Construct a test checking both output and the state. It is non-trivial to deduce the key-value of the state from the output, and having visibility of the state would be a huge win on testing. +* Investigate an incident against stateful streaming query. If users observe the incorrect output and want to track how it came up, having visibility of the state would be required. + +Users can read an instance of state store, which is matched to a single stateful operator in most cases. This means, users can expect that they can read the entire key-value pairs in the state for a single stateful operator. + +Note that there could be an exception, e.g. stream-stream join, which leverages multiple state store instances internally. The data source abstracts the internal representation away from users and +provide the users friendly approach to read the state. See the section for stream-stream join for more details. + +### Creating a State store for Batch Queries (all defaults) + +<div class="codetabs"> + +<div data-lang="python" markdown="1"> +{% highlight python %} + +df = spark \ +.readStream \ Review Comment: `spark.read.format` right ? maybe a typo everywhere ? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
