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Rahul Mahadev 47485a3c2d [SPARK-35897][SS] Support user defined initial state with flatMapGroupsWithState in Structured Streaming 
### What changes were proposed in this pull request?
This PR aims to add support for specifying a user defined initial state for arbitrary structured streaming stateful processing using [flat]MapGroupsWithState operator.

### Why are the changes needed?
Users can load previous state of their stateful processing as an initial state instead of redoing the entire processing once again.

### Does this PR introduce _any_ user-facing change?

Yes this PR introduces new API
```
  def mapGroupsWithState[S: Encoder, U: Encoder](
      timeoutConf: GroupStateTimeout,
      initialState: KeyValueGroupedDataset[K, S])(
      func: (K, Iterator[V], GroupState[S]) => U): Dataset[U]

  def flatMapGroupsWithState[S: Encoder, U: Encoder](
      outputMode: OutputMode,
      timeoutConf: GroupStateTimeout,
      initialState: KeyValueGroupedDataset[K, S])(
      func: (K, Iterator[V], GroupState[S]) => Iterator[U])

```

### How was this patch tested?

Through unit tests in FlatMapGroupsWithStateSuite

Closes #33093 from rahulsmahadev/flatMapGroupsWithState.

Authored-by: Rahul Mahadev <rahul.mahadev@databricks.com>
Signed-off-by: Gengliang Wang <gengliang@apache.org>
2021-07-02 11:53:17 +08:00
..
catalyst [SPARK-35897][SS] Support user defined initial state with flatMapGroupsWithState in Structured Streaming 2021-07-02 11:53:17 +08:00
core [SPARK-35897][SS] Support user defined initial state with flatMapGroupsWithState in Structured Streaming 2021-07-02 11:53:17 +08:00
hive [SPARK-35686][SQL] Not allow using auto-generated alias when creating view 2021-07-01 12:47:38 +00:00
hive-thriftserver [SPARK-35966][SQL] Port HIVE-17952: Fix license headers to avoid dangling javadoc warnings 2021-07-01 18:22:04 +08:00
create-docs.sh [SPARK-34010][SQL][DODCS] Use python3 instead of python in SQL documentation build 2021-01-05 19:48:10 +09:00
gen-sql-api-docs.py [SPARK-34747][SQL][DOCS] Add virtual operators to the built-in function document 2021-03-19 10:19:26 +09:00
gen-sql-config-docs.py [SPARK-32194][PYTHON] Use proper exception classes instead of plain Exception 2021-05-26 11:54:40 +09:00
gen-sql-functions-docs.py [SPARK-31562][SQL] Update ExpressionDescription for substring, current_date, and current_timestamp 2020-04-26 11:46:52 -07:00
mkdocs.yml [SPARK-30731] Update deprecated Mkdocs option 2020-02-19 17:28:58 +09:00
README.md [SPARK-30510][SQL][DOCS] Publicly document Spark SQL configuration options 2020-02-09 19:20:47 +09:00

README.md

Spark SQL

This module provides support for executing relational queries expressed in either SQL or the DataFrame/Dataset API.

Spark SQL is broken up into four subprojects:

  • Catalyst (sql/catalyst) - An implementation-agnostic framework for manipulating trees of relational operators and expressions.
  • Execution (sql/core) - A query planner / execution engine for translating Catalyst's logical query plans into Spark RDDs. This component also includes a new public interface, SQLContext, that allows users to execute SQL or LINQ statements against existing RDDs and Parquet files.
  • Hive Support (sql/hive) - Includes extensions that allow users to write queries using a subset of HiveQL and access data from a Hive Metastore using Hive SerDes. There are also wrappers that allow users to run queries that include Hive UDFs, UDAFs, and UDTFs.
  • HiveServer and CLI support (sql/hive-thriftserver) - Includes support for the SQL CLI (bin/spark-sql) and a HiveServer2 (for JDBC/ODBC) compatible server.

Running ./sql/create-docs.sh generates SQL documentation for built-in functions under sql/site, and SQL configuration documentation that gets included as part of configuration.md in the main docs directory.