Example:
dbadmin=> SELECT default_value, current_value, description
dbadmin-> FROM configuration_parameters
dbadmin-> WHERE parameter_name = 'MaxAutoSortColumns'; FROM configuration_parameters
default_value | current_value | description
---------------+---------------+-----------------------------------------------------------------------------------------
8 | 8 | Max number of columns used in auto projection sort expression (0 is to use all columns)
(1 row)
dbadmin=> CREATE TABLE test_sort_order (
dbadmin(> c1 INT,
dbadmin(> c2 INT,
dbadmin(> c3 INT,
dbadmin(> c4 INT,
dbadmin(> c5 INT,
dbadmin(> c6 INT,
dbadmin(> c7 INT,
dbadmin(> c8 INT,
dbadmin(> c9 INT,
dbadmin(> c10 INT);
CREATE TABLE
dbadmin=> INSERT INTO test_sort_order (c1) SELECT 1;
OUTPUT
--------
1
(1 row)
dbadmin=> SELECT DISTINCT projection_column_name, sort_position
dbadmin-> FROM projection_columns
dbadmin-> WHERE table_name = 'test_sort_order'
dbadmin-> AND sort_position IS NOT NULL
dbadmin-> ORDER BY sort_position;
projection_column_name | sort_position
------------------------+---------------
c1 | 0
c2 | 1
c3 | 2
c4 | 3
c5 | 4
c6 | 5
c7 | 6
c8 | 7
(8 rows)
dbadmin=> ALTER DATABASE test_db SET MaxAutoSortColumns = 4;
ALTER DATABASE
dbadmin=> DROP TABLE test_sort_order;
DROP TABLE
dbadmin=> CREATE TABLE test_sort_order (
dbadmin(> c1 INT,
dbadmin(> c2 INT,
dbadmin(> c3 INT,
dbadmin(> c4 INT,
dbadmin(> c5 INT,
dbadmin(> c6 INT,
dbadmin(> c7 INT,
dbadmin(> c8 INT,
dbadmin(> c9 INT,
dbadmin(> c10 INT);
CREATE TABLE
dbadmin=> INSERT INTO test_sort_order (c1) SELECT 1;
OUTPUT
--------
1
(1 row)
dbadmin=> SELECT DISTINCT projection_column_name, sort_position
dbadmin-> FROM projection_columns
dbadmin-> WHERE table_name = 'test_sort_order'
dbadmin-> AND sort_position IS NOT NULL
dbadmin-> ORDER BY sort_position;
projection_column_name | sort_position
------------------------+---------------
c1 | 0
c2 | 1
c3 | 2
c4 | 3
(4 rows)
Helpful Links:
https://www.vertica.com/docs/latest/HTML/Content/Authoring/AdministratorsGuide/Projections/AutoProjections.htm https://www.vertica.com/docs/latest/HTML/Content/Authoring/AdministratorsGuide/ConfiguringTheDB/ProjectionParameters.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!
