From: Vikram A [mailto:vikkiatbipl@stripped]
Sent: Wednesday, February 17, 2010 11:41 PM
To: Jerry Schwartz
Cc: MY SQL Mailing list
Subject: Re: how things get messed up
Dear Jerry Schwartz
We have applications for colleges in India. The same idea of having single table for
manipulating students records. but we are not following archiving concept.
Ex stupersonal. and stuclass these tables are playing wide role in our application. After
7 years now there are 9000 records[postgresql backend] are there in the table. Because of
this the entire application [ Fees, attendance, exams etc] performance is getting down.
For the remedy of this I proposed this year wise architecture for our new version
[mysql].
[JS] You have 9000 records? That should not slow down any application. I must not
understand you.
I have problem in year wise also, i have number of mutual related tables for students such
as stu_last_studies, stu_family_details, stu_address, stu_extracurri and so on. If i go
for year basisis i have to make all the above tables also year basis.
Hence, I feel it difficult have such number of tables after few years.
[JS] I did not mean that you should have tables for each year. I was suggesting that you
have tables for recent data and tables for archived data.
As you said the archive system, can you the idea about the archive system[If needed i will
give the table structures].
[JS] This is best described with a picture. Here is a small example of what I meant:
`student_master_table` (all years)
/\
/ \
`grades_current` `grades_archive`
| /
`class_master_table`
The structures of the two grades tables should be almost the same, something like
grade_id <autoincrement in grades_current only>
student_id <index>
class_id <index>
class_start_date
grade_received
You would add new grade records to the `grades_current` table.
Now, suppose that you don’t usually need data more than five years old. Once a year
you would run these queries:
INSERT INTO `grades_archive` SELECT * FROM `grades_current` WHERE `class_start_date` <
YEAR(DATE_SUB(NOW(), INTERVAL 4 YEAR));
DELETE FROM `grades_current` WHERE `class_start_date` < YEAR(DATE_SUB(NOW(), INTERVAL 4
YEAR));
That would keep the `grades_current` table small. If you want to find a student’s
recent grade history, you would use a query like
SELECT * FROM `grades_current` WHERE `student_id` = 12345;
If you decide that you need a student’s complete history, you could do
SELECT * FROM `grades_current` WHERE `student_id` = 12345 UNION ALL SELECT * FROM
`grades_archive` WHERE `student_id` = 12345;
That is a quick outline of what I was saying.
I don’t know how big your database is, so I can’t begin to guess whether or
not this is necessary. On my desktop computer, where I do my testing, I have two tables:
one has about 104000 records, the other has about 200000 records. The query
SELECT `prod`.`prod_num`, `prod_price`.`prod_price_del_format`,
`prod_price`.`prod_price_end_price` FROM `prod` JOIN `prod_price` ON `prod`.`prod_id` =
`prod_price`.`prod_id` WHERE `prod`.`prod_num` = 40967;
took .70 seconds. Repeating the same query with different values of `prod_num` gave
increasingly faster results, showing that caching is working as expected: after three
such queries, the response time was .14 seconds.
I understand that schools in India can be very, very big; so perhaps you need an archive
scheme such as the one I described. In fact, it might be useful to extend this whole
concept to using an archive database, rather than archive tables within the same
database. The database engine wouldn’t really care, but since the archive database
wouldn’t change very often you wouldn’t have to back it up very often,
either.
Regards,
Jerry Schwartz
The Infoshop by Global Information Incorporated
195 Farmington Ave.
Farmington, CT 06032
860.674.8796 / FAX: 860.674.8341
www.the-infoshop.com
It will be grate help to me.
Thank you
VIKRAM A
_____
From: Jerry Schwartz <jschwartz@stripped>
To: Vikram A <vikkiatbipl@stripped>; Johan De Meersman <vegivamp@stripped>
Cc: MY SQL Mailing list <mysql@stripped>
Sent: Tue, 16 February, 2010 9:32:22 PM
Subject: RE: how things get messed up
>-----Original Message-----
>From: Vikram A [mailto:vikkiatbipl@stripped]
>Sent: Friday, February 12, 2010 4:13 AM
>To: Johan De Meersman
>Cc: MY SQL Mailing list
>Subject: Re: how things get messed up
>
>Sir,
>
>Thanks for your suggestion,
>I will go for blob storage, because our application will maintain the data on
>yearly basis[stupersonal2008, stupersonal2009 etc.]. So i feel we may not
>face
>such kind of performance issue in our application.
>
[JS] It sounds like you are planning to have one table per year. Regardless of
where you put your blobs, I think that is a bad idea from a design standpoint.
It will make it harder to find historical information.
If your database is relatively small, then I'd just keep everything in one
table. If it is big, then roll data that is five years old into an archive
table. That will give you only two places, and an easy-to-follow rule to tell
you where to look.
Regards,
Jerry Schwartz
The Infoshop by Global Information Incorporated
195 Farmington Ave.
Farmington, CT 06032
860.674.8796 / FAX: 860.674.8341
www.the-infoshop.com
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