Add docs for CREATE TABLE ... AS OF SYSTEM TIME

Fixes DOC-13310

Author: rmloveland

src/current/v25.2/create-table-as.md

@@ -22,6 +22,8 @@ When the results of a query are reused multiple times within a larger query, a v
 
 A view is also advisable when the results must be up-to-date; a view always retrieves the current data from the tables that the view query mentions.
 
+{% include_cached new-in.html version="v25.2" %} Use `CREATE TABLE t AS ...` with the [`AS OF SYSTEM TIME` clause](#populate-create-table-as-with-historical-data-using-as-of-system-time) to leverage [historical reads]({% link {{ page.version.version }}/as-of-system-time.md %}) to reduce contention and improve performance.
+
 {{site.data.alerts.callout_info}}
 The default rules for [column families]({% link {{ page.version.version }}/column-families.md %}) apply.
 {{site.data.alerts.end}}
@@ -287,6 +289,34 @@ You can define the [column families]({% link {{ page.version.version }}/column-f
 (1 row)
 ~~~
 
+### Populate `CREATE TABLE AS` with historical data using `AS OF SYSTEM TIME`
+
+{% include_cached new-in.html version="v25.2" %} CockroachDB supports creating a table using historical data using the [`AS OF SYSTEM TIME`]({% link {{ page.version.version }}/as-of-system-time.md %}) clause. You can use this to create a new table based on the state of an existing table as of a specific [timestamp]({% link {{ page.version.version }}/timestamp.md %}) in the past. This is useful for:
+
+- Generating static datasets for reporting or analytical workloads without increasing contention on production tables or otherwise impacting performance.
+- Analyzing data changes over time.
+- Preserving historical data for regulatory or investigative purposes.
+
+{{site.data.alerts.callout_info}}
+The timestamp must be within the [garbage collection (GC) window]({% link {{ page.version.version }}/architecture/storage-layer.md %}#garbage-collection) of the source table for the data to be available.
+{{site.data.alerts.end}}
+
+The syntax for creating a new table from a historical table at a given timestamp is as follows; this example creates a new table at the most recent timestamp that can perform a [follower read]({% link {{ page.version.version }}/follower-reads.md %}).
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+CREATE TABLE analysis_vehicle_location_histories
+  AS SELECT * FROM vehicle_location_histories
+  AS OF SYSTEM TIME follower_read_timestamp();
+~~~
+
+~~~
+NOTICE: CREATE TABLE ... AS does not copy over indexes, default expressions, or constraints; the new table has a hidden rowid primary key column
+CREATE TABLE AS
+~~~
+
+For more information about historical reads at a given timestamp, refer to [`AS OF SYSTEM TIME`]({% link {{ page.version.version }}/as-of-system-time.md %}).
+
 ## See also
 
 - [Selection Queries]({% link {{ page.version.version }}/selection-queries.md %})
@@ -299,3 +329,6 @@ You can define the [column families]({% link {{ page.version.version }}/column-f
 - [`ALTER PRIMARY KEY`]({% link {{ page.version.version }}/alter-table.md %}#alter-primary-key)
 - [`ALTER TABLE`]({% link {{ page.version.version }}/alter-table.md %})
 - [Online Schema Changes]({% link {{ page.version.version }}/online-schema-changes.md %})
+- [`AS OF SYSTEM TIME`]({% link {{ page.version.version }}/as-of-system-time.md %})
+- [Follower Reads]({% link {{ page.version.version }}/follower-reads.md %})
+- [Disaster Recovery Planning]({% link {{ page.version.version }}/disaster-recovery-planning.md %})

src/current/v25.2/disaster-recovery-planning.md

@@ -304,6 +304,8 @@ To give yourself more time to recover and clean up the corrupted data, put your
 
 If you are within the [garbage collection window]({% link {{ page.version.version }}/configure-replication-zones.md %}#gc-ttlseconds), run [`AS OF SYSTEM TIME`]({% link {{ page.version.version }}/as-of-system-time.md %}) queries and use [`CREATE TABLE AS … SELECT * FROM`]({% link {{ page.version.version }}/create-table-as.md %}) to create comparison data and run differentials to find the offending rows to fix.
 
+{% include_cached new-in.html version="v25.2" %} Alternatively, you can use [`CREATE TABLE AS ... AS OF SYSTEM TIME`]({% link {{ page.version.version }}/create-table-as.md %}#populate-create-table-as-with-historical-data-using-as-of-system-time) to generate a copy of the data as of a specific [timestamp]({% link {{ page.version.version }}/timestamp.md %}). This also requires being within the garbage collection window.
+
 If you are outside of the garbage collection window, you will need to use a [backup]({% link {{ page.version.version }}/backup.md %}) to run comparisons.
 
 ### Restore to a point in time