Example:
By default when you add a column to a table, Vertica only adds the column to the underlying super-projections.
dbadmin=> CREATE TABLE test (c1 INT, c2 INT);
CREATE TABLE
dbadmin=> CREATE PROJECTION test_pr1 AS SELECT * FROM test;
CREATE PROJECTION
dbadmin=> CREATE PROJECTION test_pr2 AS SELECT c1 FROM test;
CREATE PROJECTION
dbadmin=> ALTER TABLE test ADD COLUMN c3 INT;
ALTER TABLE
dbadmin=> SELECT projection_name, LISTAGG(projection_column_name) columns
dbadmin-> FROM projection_columns
dbadmin-> WHERE table_name = 'test'
dbadmin-> GROUP BY projection_name;
projection_name | columns
-----------------+----------
test_pr1_b0 | c1,c2,c3
test_pr2_b1 | c1
test_pr1_b1 | c1,c2,c3
test_pr2_b0 | c1
(4 rows)
I want to add my new column to all of the projections! This time, I’ll specify the ALL PROJECTIONS option on the ALTER TABLE command.
dbadmin=> drop table test cascade;
DROP TABLE
dbadmin=> CREATE TABLE test (c1 INT, c2 INT);
CREATE TABLE
dbadmin=> CREATE PROJECTION test_pr1 AS SELECT * FROM test;
CREATE PROJECTION
dbadmin=> CREATE PROJECTION test_pr2 AS SELECT c1 FROM test;
CREATE PROJECTION
dbadmin=> ALTER TABLE test ADD COLUMN c3 INT ALL PROJECTIONS;
ALTER TABLE
dbadmin=> SELECT projection_name, LISTAGG(projection_column_name) columns
dbadmin-> FROM projection_columns
dbadmin-> WHERE table_name = 'test'
dbadmin-> GROUP BY projection_name;
projection_name | columns
-----------------+----------
test_pr1_b0 | c1,c2,c3
test_pr2_b1 | c1,c3
test_pr1_b1 | c1,c2,c3
test_pr2_b0 | c1,c3
(4 rows)
Helpful Links:https://www.vertica.com/docs/latest/HTML/Content/Authoring/SQLReferenceManual/Statements/ALTERTABLE.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!
