Question

I have a java applet what has embeeded h2 database, and table with 200.000 rows.

Table:

    CREATE TABLE `DB`.`TEST` (
        `id` INT UNSIGNED PRIMARY KEY,
        `from` VARCHAR(80)  NOT NULL,
        `from_group` SMALLINT UNSIGNED,
        `to` VARCHAR(80)  NOT NULL,
        `to_group` SMALLINT UNSIGNED,
        `type` SMALLINT UNSIGNED NOT NULL,
        `class` SMALLINT UNSIGNED NOT NULL,
        `direction` TINYINT UNSIGNED NOT NULL,
        `start` TIMESTAMP  NOT NULL,
        `answer` TIMESTAMP ,
        `end` TIMESTAMP NOT NULL,
        `duration` INT UNSIGNED,
        `bill` INT UNSIGNED,
        `cost` FLOAT UNSIGNED
    )

When i do simple query SELECT * FROM DB.TEST ORDER BY id ASC LIMIT 50 – it’s executes perfectly about 3-4 ms. But when a change order by to desc, situation is change and query takes about 8-10 seconds.

Is anyway solution to make order by faster ?

Thanks

Answer 1

H2 requires that you create a descending index in this case:

CREATE INDEX IDX_TO_DESC ON DB.TEST(TO DESC);  

That means, the index sorts this column in descending order.