Add Get The Size Of A Table as a postgres til

Author: jbranchaud

README.md

@@ -152,6 +152,7 @@ _319 TILs and counting..._
 - [Generate A UUID](postgres/generate-a-uuid.md)
 - [Generate Series Of Numbers](postgres/generate-series-of-numbers.md)
 - [Get The Size Of A Database](postgres/get-the-size-of-a-database.md)
+- [Get The Size Of A Table](postgres/get-the-size-of-a-table.md)
 - [Getting A Slice Of An Array](postgres/getting-a-slice-of-an-array.md)
 - [Insert Just The Defaults](postgres/insert-just-the-defaults.md)
 - [Integers In Postgres](postgres/integers-in-postgres.md)

postgres/get-the-size-of-a-table.md

@@ -0,0 +1,20 @@
+# Get The Size Of A Table
+
+In [Get The Size Of A Database](get-the-size-of-a-database.md), I showed a
+PostgreSQL administrative function, `pg_database_size()`, that gets the size
+of a given database. With the `pg_relation_size()` function, we can get the
+size of a given table. For instance, if we'd like to see the size of the
+`reservations` table, we can executing the following query:
+
+```sql
+> select pg_relation_size('reservations');
+ pg_relation_size
+------------------
+          1531904
+```
+
+This gives us the size of the `reservations` table in bytes. As you might
+expect, the referenced table needs to be part of the connected database and
+on the search path.
+
+See [the Postgres docs](http://www.postgresql.org/docs/current/static/functions-admin.html) for more details.