How to get last 10 rows in a table on a large database? - Mailing list pgsql-sql

Hi,

Does anyone have a good idea to get the last 10 rows from a table? I
tried 

SELECT * FROM table ORDER BY datetime DESC LIMIT 10

But my table has over 1 million rows, so this takes forever.. anyone
has a better idea on how to do this? 

Alex
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