Document unnamed prepared statements

Author: levkk

docs/configuration/pgdog.toml/general.md

@@ -303,10 +303,11 @@ Enables support for prepared statements. Available options are:
 
 - `disabled`
 - `extended`
+- `extended_anonymous`
 - `full`
 
 Full enables support for rewriting prepared statements sent over the simple protocol. Extended handles prepared statements sent normally
-using the extended protocol. `full` attempts to rewrite prepared statements sent using the simple protocol.
+using the extended protocol. `full` attempts to rewrite prepared statements sent using the simple protocol. `extended_anonymous` caches and rewrites unnamed prepared statements, which is useful for some legacy client drivers.
 
 Default: **`extended`**
 

docs/features/prepared-statements.md

@@ -81,3 +81,14 @@ prepared_statements = "full"
 
 Statements prepared using this method can be executed normally with `Bind` and `Execute` messages. Result data types can be inspected with `Describe`, just
 like a regular prepared statement.
+
+## Unnamed statements
+
+By default, unnamed (or anonymous) prepared statements are not cached and are sent to Postgres as-is. This works fine for most client drivers because they send the entire query in a single request. However, some drivers, like `go/pq` do not.
+
+To make those drivers work, consider caching and rewriting unnamed prepared statements, like so:
+
+```toml
+[general]
+prepared_statements = "extended_anonymous"
+```