Updating Fusion thread information (#8554)

Author: matthewshaver

website/docs/docs/dbt-versions/core-upgrade/03-upgrading-to-fusion.md

@@ -7,7 +7,8 @@ displayed_sidebar: "docs"
 
 import FusionAdapters from '/snippets/_fusion-dwh.md';
 import FusionUpgradeSteps from '/snippets/_fusion-upgrade-steps.md';
-import FusionLifecycle from '/snippets/_fusion-lifecycle-callout.md'
+import FusionLifecycle from '/snippets/_fusion-lifecycle-callout.md';
+import FusionThreads from '/snippets/_fusion-threads.md';
 
 <FusionLifecycle />
 
@@ -238,7 +239,11 @@ In Fusion, `dbt build` runs _all_ of the unit tests _first_, and then build the
 
 dbt Core runs with `--threads 1` by default. You can increase this number to run more nodes in parallel on the remote data platform, up to the max parallelism enabled by the DAG.
 
-In Fusion, if `--threads` is not set, or set to `--threads 0`, dbt will use a per-adapter default value for maximum threads. Some data platforms can handle more concurrent connections than others. If there is a user-configured value for `--threads` (via CLI flag or `profiles.yml`), Fusion will use it.
+<Constant name="fusion"/>  handles threading differently depending on your data platform:
+
+<FusionThreads />
+
+For more information, refer to [Using threads](/docs/running-a-dbt-project/using-threads#fusion-engine-thread-optimization).
 
 #### Continue to compile unrelated nodes after hitting a compile error
 

website/docs/docs/fusion/about-fusion.md

@@ -45,11 +45,14 @@ Fusion also enables more-efficient deployments of large DAGs. By tracking which
 
 ### Thread management
 
-The <Constant name="fusion_engine" /> manages parallelism differently than <Constant name="core" />. Rather than treating the `threads` setting as a strict limit on concurrent operations, Fusion dynamically optimizes parallelism based on the selected warehouse.
+The <Constant name="fusion_engine" /> manages parallelism differently than <Constant name="core" />. Rather than treating the `threads` setting as a strict limit on concurrent operations, Fusion optimizes parallelism based on each adapter's characteristics.
 
-In Redshift, the `threads` setting limits the number of queries or statements that can run in parallel, which is important for managing Redshift's concurrency limits. In other warehouses, Fusion dynamically adjusts thread usage based on each warehouse's capabilities, using your thread configuration as guidance while automatically optimizing for maximum efficiency.
+- **Snowflake and Databricks**: Fusion ignores user-set threads and automatically optimizes parallelism for maximum performance.
+- **BigQuery and Redshift**: Fusion respects user-set threads to manage rate limits and concurrency constraints.
 
-For more information, refer to [Using threads](/docs/running-a-dbt-project/using-threads#fusion-engine-thread-behavior).
+For BigQuery and Redshift, setting `--threads 0` or omitting the setting allows Fusion to dynamically optimize. Low thread values can significantly slow down performance on these platforms.
+
+For more information, refer to [Using threads](/docs/running-a-dbt-project/using-threads#fusion-engine-thread-optimization).
 
 ### How to use Fusion
 

website/docs/docs/running-a-dbt-project/using-threads.md

@@ -5,6 +5,7 @@ sidebar_label: "Use threads"
 description: "Understand what threads mean and how to use them."
 pagination_next: null
 ---
+import FusionThreads from '/snippets/_fusion-threads.md';
 
 When dbt runs, it creates a directed acyclic graph (DAG) of links between models. The number of threads represents the maximum number of paths through the graph dbt may work on at once – increasing the number of threads can minimize the run time of your project.
 
@@ -25,17 +26,14 @@ You will define the number of threads in your `profiles.yml` file (when developi
 
 ## Fusion engine thread optimization
 
-The <Constant name="fusion_engine" /> handles threading differently than <Constant name="core" />. The legacy `threads` setting doesn't act as a strict limit on the number of threads created. Instead, Fusion manages parallelism dynamically based on the selected warehouse.
+The <Constant name="fusion_engine" /> handles threading differently than <Constant name="core" />. Rather than treating `threads` as a strict limit, <Constant name="fusion"/> manages parallelism based on each adapter's characteristics.
 
-### Redshift
+### Adapter-specific behavior
 
-In Redshift, the `threads` setting limits the number of queries or statements that can run in parallel. This behavior is the same as <Constant name="core" />, and is important for managing Redshift's concurrency limits and query queue behavior.
 
-### Other warehouses
+<FusionThreads />
 
-In other warehouses, Fusion dynamically optimizes thread usage based on the DAG and warehouse concurrency properties.
-
-For more information about Fusion's approach to parallelism, refer to [the dbt Fusion engine](/docs/fusion) page.
+For more information about <Constant name="fusion"/>'s approach to parallelism, refer to [the <Constant name="fusion_engine"/>](/docs/fusion) page.
 
 </VersionBlock>
 

website/snippets/_fusion-threads.md

@@ -0,0 +1,6 @@
+| Adapter | Behavior |
+|---------|----------|
+| **Snowflake** | Fusion ignores user-set threads and automatically optimizes parallelism for maximum performance. <br></br> The only supported override is `threads: 1`, which can also help resolve timeout issues if set. 
+| **Databricks** | Fusion ignores user-set threads and automatically optimizes parallelism for maximum performance. <br></br> The only supported override is `threads: 1`, which can also help resolve timeout issues if set. |
+| **BigQuery** | Fusion respects user-set threads to manage API rate limits. <br></br> Setting `--threads 0` (or omitting the setting) allows <Constant name="fusion"/> to dynamically optimize parallelism. |
+| **Redshift** | Fusion respects user-set threads to manage concurrency limits.<br></br> Setting `--threads 0` (or omitting the setting) allows <Constant name="fusion"/> to dynamically optimize parallelism. |