Merge pull request #3989 from ClickHouse/nickitat-patch-1

Add projections to the list of unsupported features with parallel replicas

Author: Blargian

docs/deployment-guides/parallel-replicas.mdx

@@ -312,6 +312,7 @@ the label `comp-parallel-replicas`.
 | Complex queries                                 | Currently parallel replica works fairly well for simple queries. Complexity layers like CTEs, subqueries, JOINs, non-flat query, etc. can have a negative impact on query performance.                                                                                                                                                                                                                                                                                   |
 | Small queries                                 | If you are executing a query that does not process a lot of rows, executing it on multiple replicas might not yield a better performance time given that the network time for the coordination between replicas can lead to additional cycles in the query execution. You can limit these issues by using the setting: [`parallel_replicas_min_number_of_rows_per_replica`](/docs/operations/settings/settings#parallel_replicas_min_number_of_rows_per_replica).  |
 | Parallel replicas are disabled with FINAL      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
+| Projections are not used together with Parallel replicas      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
 | High Cardinality data and complex aggregation | High cardinality aggregation that needs to send much data can significantly slow down your queries.                                                                                                                                                                                                                                                                                                                                                                     |
 | Compatibility with the new analyzer           | The new analyzer might significantly slow down or speed up query execution in specific scenarios.                                                                                                                                                                                                                                                                                                                                                                       |
 
@@ -504,4 +505,4 @@ SETTINGS allow_experimental_parallel_reading_from_replicas=2
 FORMAT TSV;
 ```
 
-<Image img={image_9} size="lg" alt="EXPLAIN with parallel_replica"/>
+<Image img={image_9} size="lg" alt="EXPLAIN with parallel_replica"/>