How to prevent the default primary key indexing is from being used in VoltDB?

Question

For VoltDB, while creating the table, I am using primary key to prevent content violation. This creates primary key index automatically which is a balance tree. I have also create Hash index for the tables and I want to use hash index and not to use primary key index. Is there any setting that I can make to use the Hash index while execution of queries.

Answer 1

VoltDB uses a convention to determine whether to use a red-black tree index or a hash index. The convention is to include the substring "hash" (case-insensitive) within the name of the index. It can be a prefix, suffix, or somewhere in the middle of the name.

In my experience, since the index is entirely in-memory, the is very little difference in performance between a tree and hash index. It may be worthwhile to try it both ways and compare the performance vs. space usage to decide which is best.

Also, there are a few syntax styles for declaring the primary key of a table. You do not have to give it a name, but you can, which would allow you to declare whether you want it to be a tree or hash index. There should be no need to create duplicate indexes simply because the primary key index was not as you wanted it. Below are two examples:

CREATE TABLE Version (
    Major SMALLINT NOT NULL,
    Minor SMALLINT NOT NULL,
    baselevel INTEGER NOT NULL,
    ReleaseDate TIMESTAMP,
    CONSTRAINT Version_Hash_Idx PRIMARY KEY 
        (Major, Minor, Baselevel)  -- hash index
);

CREATE TABLE Version (
    Major SMALLINT NOT NULL,
    Minor SMALLINT NOT NULL,
    baselevel INTEGER NOT NULL,
    ReleaseDate TIMESTAMP,
    PRIMARY KEY (Major, Minor, Baselevel)  -- default tree index
);