chore: update troubleshooting info for DISTINCT. (#3461)

* chore: update troubleshooting info for DISTINCT.

_partials/_caggs-function-support.md

@@ -1,12 +1,49 @@
-This table summarizes aggregate function support in continuous aggregates:
+
+The following table summarizes the aggregate functions supported in continuous aggregates:
 
 |Function, clause, or feature|TimescaleDB 2.6 and earlier|TimescaleDB 2.7, 2.8, and 2.9|TimescaleDB 2.10 and later|
 |-|-|-|-|
 |Parallelizable aggregate functions|✅|✅|✅|
-|Non-parallelizable aggregate functions|❌|✅|✅|
+|[non-parallelizable SQL aggregates][postgres-parallel-agg]|❌|✅|✅|
 |`ORDER BY`|❌|✅|✅|
 |Ordered-set aggregates|❌|✅|✅|
 |Hypothetical-set aggregates|❌|✅|✅|
 |`DISTINCT` in aggregate functions|❌|✅|✅|
 |`FILTER` in aggregate functions|❌|✅|✅|
 |`FROM` clause supports `JOINS`|❌|❌|✅|
+
+
+DISTINCT works in aggregate functions not in the query definition. For example, for the table:
+
+```sql
+CREATE TABLE public.candle(
+symbol_id uuid                     NOT NULL,
+symbol    text                     NOT NULL,
+"time"    timestamp with time zone NOT NULL,
+open      double precision         NOT NULL,
+high      double precision         NOT NULL,
+low       double precision         NOT NULL,
+close     double precision         NOT NULL,
+volume    double precision         NOT NULL
+);
+
+```
+- The following works:
+  ```sql
+  CREATE MATERIALIZED VIEW candles_start_end
+  WITH (timescaledb.continuous) AS
+  SELECT time_bucket('1 hour', "time"), COUNT(DISTINCT symbol), first(time, time) as first_candle, last(time, time) as last_candle
+  FROM candle
+  GROUP BY 1;
+  ```
+- This does not:
+  ```sql
+  CREATE MATERIALIZED VIEW candles_start_end
+  WITH (timescaledb.continuous) AS
+  SELECT DISTINCT ON (symbol)
+  symbol,symbol_id, first(time, time) as first_candle, last(time, time) as last_candle
+  FROM candle
+  GROUP BY symbol_id;
+  ```
+
+[postgres-parallel-agg]: https://www.postgresql.org/docs/current/parallel-plans.html#PARALLEL-AGGREGATION

_troubleshooting/caggs-queries-fail.md

@@ -3,11 +3,6 @@ title: Queries fail when defining continuous aggregates but work on regular tabl
 section: troubleshooting
 products: [cloud, mst, self_hosted]
 topics: [continuous aggregates]
-errors:
-  - language: sql
-    message: |-
-      ERROR:  invalid continuous aggregate view
-      SQL state: 0A000
 apis:
   - [continuous aggregates, CREATE MATERIALIZED VIEW (Continuous Aggregate)]
 keywords: [continuous aggregates]
@@ -16,22 +11,15 @@ tags: [continuous aggregates, query]
 
 import CaggsFunctionSupport from 'versionContent/_partials/_caggs-function-support.mdx';
 
-<!---
-* Use this format for writing troubleshooting sections:
- - Cause: What causes the problem?
- - Consequence: What does the user see when they hit this problem?
- - Fix/Workaround: What can the user do to fix or work around the problem? Provide a "Resolving" Procedure if required.
- - Result: When the user applies the fix, what is the result when the same action is applied?
-* Copy this comment at the top of every troubleshooting page
--->
-
-Continuous aggregates don't work on all queries. If you are using a function
-that continuous aggregates do not support, you see the error above.
+Continuous aggregates do not work on all queries. For example, TimescaleDB does not support window functions on 
+continuous aggregates. If you use an unsupported function, you see the following error:
 
-TimescaleDB doesn't support window functions on continuous aggregates.
-In versions earlier than 2.7, it doesn't support any
-[non-parallelizable SQL aggregates][postgres-parallel-agg].
+```sql
+      ERROR:  invalid continuous aggregate view
+      SQL state: 0A000
+```
 
 <CaggsFunctionSupport />
 
+
 [postgres-parallel-agg]: https://www.postgresql.org/docs/current/parallel-plans.html#PARALLEL-AGGREGATION