Add Pretty Print Data Sizes as a postgres til

Author: jbranchaud

README.md

@@ -164,6 +164,7 @@ _321 TILs and counting..._
 - [List Database Users](postgres/list-database-users.md)
 - [Max Identifier Length Is 63 Bytes](postgres/max-identifier-length-is-63-bytes.md)
 - [pg Prefix Is Reserved For System Schemas](postgres/pg-prefix-is-reserved-for-system-schemas.md)
+- [Pretty Print Data Sizes](postgres/pretty-print-data-sizes.md)
 - [Restart A Sequence](postgres/restart-a-sequence.md)
 - [Restarting Sequences When Truncating Tables](postgres/restarting-sequences-when-truncating-tables.md)
 - [Send A Command To psql](postgres/send-a-command-to-psql.md)

postgres/pretty-print-data-sizes.md

@@ -0,0 +1,38 @@
+# Pretty Print Data Sizes
+
+Use the `pg_size_pretty()` function to pretty print the sizes of data. Given
+a `bigint`, it will determine the most human-readable format with which to
+print the value:
+
+```sql
+> select pg_size_pretty(1234::bigint);
+ pg_size_pretty
+----------------
+ 1234 bytes
+
+> select pg_size_pretty(123456::bigint);
+ pg_size_pretty
+----------------
+ 121 kB
+
+> select pg_size_pretty(1234567899::bigint);
+ pg_size_pretty
+----------------
+ 1177 MB
+
+> select pg_size_pretty(12345678999::bigint);
+ pg_size_pretty
+----------------
+ 11 GB
+```
+
+This function is particularly useful when used with the
+[`pg_database_size()`](get-the-size-of-a-database.md) and
+[`pg_relation_size()`](get-the-size-of-a-table.md) functions.
+
+```sql
+> select pg_size_pretty(pg_database_size('hr_hotels'));
+ pg_size_pretty
+----------------
+ 12 MB
+```