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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Created] (PHOENIX-4550) Allow declaration of max columns on base physical table
Date Tue, 23 Jan 2018 03:15:00 GMT
James Taylor created PHOENIX-4550:
-------------------------------------

             Summary: Allow declaration of max columns on base physical table
                 Key: PHOENIX-4550
                 URL: https://issues.apache.org/jira/browse/PHOENIX-4550
             Project: Phoenix
          Issue Type: Bug
            Reporter: James Taylor


By declaring the max number of columns on a base table, we can optimize the storage for SINGLE_CELL_ARRAY_WITH_OFFSETS
by not storing null values for the columns preceding the initial column of a view. This will
make a huge difference in storage when you have a base table with many views. For example:

{code}
-- Declare that the base table will have no more than 10 columns
CREATE IMMUTABLE TABLE base (k1 VARCHAR, prefix CHAR(3) v1 DATE,
    CONSTRAINT pk PRIMARY KEY (k1, prefix))
    MULTI_TENANT = true,
    MAX_COLUMNS = 10;
CREATE VIEW v1(k2 VARCHAR PRIMARY KEY, v2 VARCHAR, v3 VARCHAR)
    AS SELECT * FROM base WHERE prefix = 'A00';
CREATE VIEW v2(k2 VARCHAR PRIMARY KEY, v2 VARCHAR, v3 VARCHAR);
    AS SELECT * FROM base WHERE prefix = 'A10';
...
{code}

As the number of views grow, the difference between the base table column encoding (column
#1) and the starting column number of the view (since the starting offset is determined by
an incrementing value on the base table) will increase. This bloats the storage as we need
to store null values for column encodings between the base table column and the starting column
of the view.

Instead, we'll pass through the MAX_COLUMNS value for queries and anything column encoding
less than this we know it'll be at the start. Anything greater and we'll start the search
from <column encoding> - <minimum view column encoding>.



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