提高 JDBC 查询的性能 - ArrayList 比较

Question

I've been trying to get the most efficient way to get a set of values from a DB and comparing them with their respective sub-string to save specific values... Here is an example:
I have this table which contains a PRODUCT(ID), from the ones in LVL - 7 I have to substring the values until I get to LVL1

LVL     PRODUCT          DESCRIPTION
5       01AR2TGELL       DESLVL5
6       01AR2TGELLGS     DESLVL6
7       01AR2TGELLGSQKA  DESLVL7
6       01AR2TGELLDE     DESLVL6
7       01AR2TGELLDEUDP  DESLVL7
7       01AR2TGELLDEUZN  DESLVL7

So I can get something like this:

LVL   PRODUCT          DESCRIPTION  | LVL   PRODUCT        DESCRIPTION  | LVL  PRODUCT     DESCRIPTION
7     01AR2TGELLGSQKA  DESLVL7      | 6     01AR2TGELLGS   DESLVL6      | 5    01AR2TGELL  DESLVL5
7     01AR2TGELLDEUDP  DESLVL7      | 6     01AR2TGELLDE   DESLVL6      | 5    01AR2TGELL  DESLVL5
7     01AR2TGELLDEUZN  DESLVL7      | 6     01AR2TGELLDE   DESLVL6      | 5    01AR2TGELL  DESLVL5

I'm working with Java (Requirement) and also I'm using JDBC to connect to the Oracle DB. What I did is to get all the values from LVL7 with a query and save all those values in an ArrayList then, with a LVL and a Value of the PRODUCT Substring I compare the values, like this:

"select * from PRODHIERARCHY where LVL=7"
"select * from PRODHIERARCHY WHERE LVL= 6 AND PRODUCT_HIERARCHY="+"'"+descLv7.get(j).substring(0, descLv7.get(j).length() - 4)+"'"

My problem is, there is approx. 35 thousand LVL7 values, and in total around 65 thousand so this is very inefficient. (To get the 35 thousand LVL7 values takes around 3 minutes since the DB is processing everything, when it gets to the comparison with the ArrayList it takes around 30 minutes per LVL).

Can anyone please recommend me a way to modify either the query or my comparison process so it takes about the same time as the first query? Thanks!

Answer 1

Note: I don't have Oracle, so I made it with MSSQL, just use substr instead of left for the artificial keys.

Here's an static idea. Lets see, first let us create a view with some computed columns (artificial keys) (or you could add them to your product table and index them)

create view vw_product_computed as
select
    a.lvl,
    a.Product,
    left(a.product, 12) as a12, -- your first lelvel down (artificial key) 
    left(a.product, 10) as a10  -- your seccond level down (artificial key) 
from
    products a;

Then is just a matter of joining your product table with your view using your artificial keys:

select
    *
from
    desarrollo.vw_product_computed a
join dbo.products b on b.product = a.a12
join dbo.products c on c.product = a.a10
where
    a.lvl = 7;

And off you go, you have your result set as you need it:

If you would like to make it a dynamic thing I guess a pivot table may come in handy.

Hope this helps mate.