Add Sleeping as a postgres til.

postgres/sleeping.md

@@ -0,0 +1,32 @@
+# Sleeping
+
+Generally you want your SQL statements to run against your database as
+quickly as possible. For those times when you are doing some sort of
+debugging or just want your queries to look very computationally expensive,
+PostgreSQL offers the `pg_sleep` function.
+
+To sleep for 5 seconds, try the following:
+
+```sql
+> select now(); select pg_sleep(5); select now();
+              now
+-------------------------------
+ 2016-01-08 16:30:21.251081-06
+(1 row)
+
+Time: 0.274 ms
+ pg_sleep
+----------
+
+(1 row)
+
+Time: 5001.459 ms
+              now
+-------------------------------
+ 2016-01-08 16:30:26.252953-06
+(1 row)
+
+Time: 0.260 ms
+```
+
+As you'll notice, the `pg_sleep` statement took about 5 seconds.