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What is the "d - determine" constraint type?
Posted: Thu May 15, 2014 8:46 pm
by Julie
Hi,
From the docs I see that Vertica 7 supports the constraint types:
- c — check is reserved, but not supported
f - foreign
n - not null
p - primary
u - unique
d - determines
What is the "d - determine" constraint type?
Re: What is the "d - determine" constraint type?
Posted: Mon May 19, 2014 3:14 am
by JimKnicely
The "determines" constraints is created when a column correlation is defined. For example:
Code: Select all
dbadmin=> create table test (a int, b int, c int primary key);
CREATE TABLE
dbadmin=> alter table test add constraint t_cor correlation (b) determines (a);
ALTER TABLE
dbadmin=> select constraint_name, table_name, constraint_type from table_constraints where table_name = 'test';
constraint_name | table_name | constraint_type
-----------------+------------+-----------------
C_PRIMARY | test | p
t_cor | test | d
(2 rows)
Re: What is the "d - determine" constraint type?
Posted: Tue Nov 10, 2015 3:23 pm
by avoronin
Hello All,
Can someone explain what this "correlation detarmines" constraint means ?
Re: What is the "d - determine" constraint type?
Posted: Wed Nov 11, 2015 2:44 pm
by JimKnicely
http://my.vertica.com/docs/7.2.x/HTML/i ... %7C_____34
When creating a design, Database Designer can:
- Analyze correlated columns.
- Order the correlated columns in a way that maximizes the compression ratio.
- Place them early in the projection sort order.
- Choose Run-Length Encoding (RLE) for the columns that satisfy the recommended RLE criteria.