That is, instead of joining two large fact tables together, combine them into a single table!
Example:
dbadmin=> \d big1;
List of Fields by Tables
Schema | Table | Column | Type | Size | Default | Not Null | Primary Key | Foreign Key
--------+-------+--------+------+------+---------+----------+-------------+-------------
public | big1 | a | int | 8 | | f | f |
(1 row)
dbadmin=> \d big2;
List of Fields by Tables
Schema | Table | Column | Type | Size | Default | Not Null | Primary Key | Foreign Key
--------+-------+--------+------+------+---------+----------+-------------+-------------
public | big2 | b | int | 8 | | f | f |
(1 row)
dbadmin=> SELECT COUNT(*) FROM big1;
COUNT
------------
5000000000
(1 row)
dbadmin=> SELECT COUNT(*) FROM big2;
COUNT
------------
5000000000
(1 row)
dbadmin=> \timing
Timing is on.
dbadmin=> SELECT COUNT(*) FROM big1 JOIN big2 ON b = a;
COUNT
------------
5000000000
(1 row)
Time: First fetch (1 row): 352338.000 ms. All rows formatted: 352338.038 ms
dbadmin=> SELECT COUNT(b) FROM big1 JOIN big2 ON b = a;
COUNT
------------
5000000000
(1 row)
Time: First fetch (1 row): 311465.060 ms. All rows formatted: 311465.092 ms
dbadmin=> CREATE TABLE big1_big2 AS SELECT a, b FROM big1 JOIN big2 ON b = a;
CREATE TABLE
Time: First fetch (0 rows): 1192135.459 ms. All rows formatted: 1192135.481 ms
dbadmin=> SELECT COUNT(b) FROM big1_big2;
COUNT
------------
5000000000
(1 row)
Time: First fetch (1 row): 15068.069 ms. All rows formatted: 15080.214 ms
Helpful Links:https://www.vertica.com/docs/latest/HTML/Content/Authoring/AnalyzingData/FlattenedTables/FlattenedTables.htm
Have fun!
About the Author
James Knicely
Vertica Field Chief Technologist
I've had the privilege of working with many database technologies in my career. But after being introduced to Vertica in May of 2011 as a client, I was hooked on the new technology after witnessing a query run in milliseconds that had previously ran for hours on the legacy database we had in place. It was then that I knew I wanted to eventually join the Vertica team, and 4 years later I did! I am currently a Vertica evangelist and am ready to help you get on board! Please feel free to reach out to me with any questions you have about Vertica and make sure to follow my Vertica Quick Tips!
