How to add existing table column in existing projection segmented by hash clause in vertica db? - projection

Question

I have created one table and have one projection of that table. I have to add existing table column in existing projection segmented by hash clause in vertica db.
"I have to add SBS_ALERT_ID column in existing projection segmented by hash clause without creating new projection."
CREATE TABLE public.ALERT
(
AS_OF_DATE date,
ALERT_ID int,
LOAN_NUMBER varchar(20),
SERVICER_LOAN_NUMBER varchar(20),
SBS_LOAN_NUMBER varchar(20),
SBS_ALERT_ID int,
ALERT_TYPE_ID varchar(25),
);
CREATE PROJECTION public.ALERTTT_SEG /*+createtype(D)*/
(
AS_OF_DATE ENCODING RLE,
ALERT_ID ENCODING DELTARANGE_COMP,
LOAN_NUMBER ENCODING ZSTD_FAST_COMP,
SERVICER_LOAN_NUMBER,
SBS_LOAN_NUMBER ENCODING RLE,
SBS_ALERT_ID ENCODING DELTARANGE_COMP,
ALERT_TYPE_ID,
)
AS
SELECT ALERT.AS_OF_DATE,
ALERT.ALERT_ID,
ALERT.LOAN_NUMBER,
ALERT.SERVICER_LOAN_NUMBER,
ALERT.SBS_LOAN_NUMBER,
ALERT.SBS_ALERT_ID,
ALERT.ALERT_TYPE_ID,
FROM public.ALERT
ORDER BY ALERT.LOAN_NUMBER,
ALERT.SBS_LOAN_NUMBER
SEGMENTED BY hash(ALERT.LOAN_NUMBER, ALERT.SBS_LOAN_NUMBER) ALL NODES;

Answer 1

Do you mean something like this?
Initial situation:
CREATE TABLE segby (
fullname varchar(12),
dob date
);
CREATE PROJECTION segby_super /*+basename(segby),createtype(A)*/ (
fullname,
dob
)
AS
SELECT segby.fullname,
segby.dob
FROM segby
ORDER BY segby.fullname,
segby.dob
SEGMENTED BY hash(segby.dob, segby.fullname) ALL NODES OFFSET 0;
Then, you add a column and initialise it with a DEFAULT ...
ALTER TABLE segby ADD id INT NOT NULL DEFAULT HASH(dob,fullname);
And subsequently, you make sure the table is segmented by that new column, by creating such a projection:
CREATE PROJECTION segby_id
AS SELECT
id
, fullname
, dob
FROM segby
ORDER BY id
SEGMENTED BY HASH(id) ALL NODES;
And finish by running a REFRESH on your table ...
SELECT REFRESH('segby');
-- out REFRESH
-- out -
-- out Refresh completed with the following outcomes:
-- out Projection Name: [Anchor Table] [Status] [Refresh Method] [Error Count] [Duration (sec)]
-- out ----------------------------------------------------------------------------------------
-- out "dbadmin"."segby_id": [segby] [refreshed] [scratch] [0] [0]
For your specific question: It looks as if you would like to be able to fire a command like:
ALTER PROJECTION public.ALERTTT_SEG
SEGMENTED BY hash(ALERT.LOAN_NUMBER, ALERT.SBS_LOAN_NUMBER,ALERT.SBS_ALERT_ID) ALL NODES;
This simply does not work.
You will have to create a new projection, segmented the new way, refresh the table, and drop the original projection