Added information about external connection pools

Author: chandr-andr

docs/.vuepress/sidebar.ts

@@ -77,6 +77,11 @@ export default sidebar({
         "opentelemetry",
       ],
     },
+    {
+      text: "External connection pools",
+      prefix: "/extra_conn_pools",
+      link: "/external_connection_pools.md"
+    },
     {
       text: "Contribution guide",
       prefix: "/contribution_guide",

docs/external_connection_pools.md

@@ -0,0 +1,25 @@
+---
+title: External connection pools
+---
+
+PSQLPy supports external connection pools like [PgBouncer](https://www.pgbouncer.org/) or [Supavisor](https://github.com/supabase/supavisor).
+
+Usually, external connection pools have 3 main [modes](https://www.pgbouncer.org/features.html): `Session`, `Transaction` and `Statement`.
+
+If you use `Session` mode, there is nothing you have to do, just use PSQLPy as usual.
+
+But there are a few conditions that must be met to make `Transaction` and `Statement` work.
+
+### Disable statement preparation
+Disable statement preparation for any sql statement execution (if a method has `prepared` parameter, set it to `False`).
+
+### Execute statement only in transaction
+Each statement must be executed in a transaction.
+
+```python
+db_pool = ConnectionPool(...)
+
+async with db_pool.acquire() as conn:
+    async with conn.transaction() as transaction:
+        await transaction.execute("SELECT 1", prepared=False)
+```