Reuse or Create SparkSession

Author: jaceklaskowski

docs/jvm/SparkSession.Builder.md

@@ -26,7 +26,7 @@ create(): SparkSession
 
 `create` [setDefaultAndActiveSession](#setDefaultAndActiveSession) and then [applyOptions](#applyOptions).
 
-## Try to Create New Session from SparkConnectClient { #tryCreateSessionFromClient }
+## Try to Create New Session for SparkConnectClient { #tryCreateSessionFromClient }
 
 ```scala
 tryCreateSessionFromClient(): Option[SparkSession]
@@ -47,3 +47,40 @@ Otherwise, `tryCreateSessionFromClient` returns no `SparkSession`.
 `tryCreateSessionFromClient` is used when:
 
 * `SparkSession.Builder` is requested to [create a new SparkSession](#create) and [getOrCreate a SparkSession](#getOrCreate)
+
+## Reuse or Create SparkSession { #getOrCreate }
+
+??? note "SparkSessionBuilder"
+
+    ```scala
+    getOrCreate(): SparkSession
+    ```
+
+    `getOrCreate` is part of the `SparkSessionBuilder` ([Spark SQL]({{ book.spark_sql }}/SparkSessionBuilder.md#getOrCreate)) abstraction.
+
+??? note "Public API"
+    `getOrCreate` is part of the public API.
+
+???+ warning "Generative AI"
+    This description was co-authored using Generative AI tools, namely [JetBrains AI Assistant](https://www.jetbrains.com/ai/) (with the [openai-gpt-4o](https://openai.com/index/hello-gpt-4o/) model).
+
+    Prompt: "What does getOrCreate do? Please explain every line."
+
+`getOrCreate` either returns an existing `SparkSession` (that matches the configuration provided) or creates a new `SparkSession` instance if no suitable session exists.
+
+`getOrCreate` is used to ensure that a `SparkSession` is always available without having to worry whether a session already exists.
+
+`getOrCreate` uses a caching mechanism alongside proper configuration and session updates.
+
+---
+
+`getOrCreate` [starts a local Spark Connect server](SparkSession.md#withLocalConnectServer) unless already started.
+
+`getOrCreate` [attempts to create a session by directly reusing the current client (if it exists and is valid)](#tryCreateSessionFromClient).
+If a valid client exists, a new `SparkSession` is built and returned immediately.
+
+Otherwise (if no valid client exists or the session is not reusable), `getOrCreate` finds the `SparkSession` (in the [sessions](SparkSession.md#sessions) by the [Configuration](#configuration)) or creates a session.
+
+`getOrCreate` updates the global default and/or active `SparkSession` in the application.
+
+`getOrCreate` applies [`spark.sql`-prefixed options](SparkSession.md#sparkOptions) and the builder's options to the new or existing session.