time estimation for a test - Mailing list pgsql-general

From salah jubeh
Subject time estimation for a test
Date
Msg-id 553521.44154.qm@web161513.mail.bf1.yahoo.com
Whole thread Raw
List pgsql-general
Hello,

I have a view which is a result of the cross product of three tables, I want to test how much time is required to populate this view. Also, I want to test the scalability of this view in the future. Since, I have already live data I am wondering if I can do that without creating an automatic data generation i.e

time psql  -c 'SELECT * FROM view limit 100'
time psql  -c 'SELECT * FROM view limit 200'
...
time psql  -c 'SELECT * FROM view limit 10000'


Also, I would like to do a hot and cold tests. How Can I do the cold tests on Postgres, should I shut down and restart the server ? or there are some commands to clear the DBMS buffer.

How can I test this using a formula. The time to calculate the view is proportional to the cross product of the three tables i.e

view (t) =  number of rows of table1 * number of rows table2 * number of rows table3.  Since I am doing cross product I assume a sequential scan will be used for data retrial from the H.D for all tables. What are other parameters I need to include in this formula and How I can get it. i.e I know that the row size is one factor and the time to read a data page on the H.D. is another one.

Regards



 

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