topic Big table of users (efficient sql select) in QlikView

Big table of users (efficient sql select)

Wed, 11 Nov 2015 15:27:27 GMT

Hi guys,

I have a User table with almost 500 million records and I have been including it partially in the model like this:

left Keep (Fact)

load * ;

sql select * from Users;

(Both tables join on user ID)

However, this approach looks into the entire 500M record table, before it joins with the users contained in the fact table, which takes quite a while. Is there a better approach? Is there a way to SQL Select with a where clause, using the distinct users from the Fact table, for example?

All help is appreciated.

Thank you.

Nuno

Re: Big table of users (efficient sql select)

sunny_talwar — Wed, 11 Nov 2015 15:29:04 GMT

You can store the distinct list of user ID in a variable and use that variable in your SQL Where clause. I have done something similar before, will check if I can get hold of that example.

Re: Big table of users (efficient sql select)

Anonymous — Wed, 11 Nov 2015 15:36:10 GMT

Does your Fact table exist in SQL outside of QlikView without a great deal of QVS load logic? If so, perhaps just

SELECT user.* FROM user INNER JOIN fact ON user.userid = fact.userid;

Let the DBMS do the heavy lifting.

Re: Big table of users (efficient sql select)

Colin-Albert — Wed, 11 Nov 2015 15:42:48 GMT

Do you need all fields from the Users table?

Select * can be slower than selecting just the fields you need.

Also consider using a mapping table and applymap rather than joining the data.

It can be quicker to create and apply several mapping tables rather than joining.

Re: Big table of users (efficient sql select)

Fri, 13 Nov 2015 10:01:37 GMT

That seems like the way I want to go. If you find a good example, please let me know.

Thanks,

Nuno

Re: Big table of users (efficient sql select)

maxgro — Fri, 13 Nov 2015 10:09:20 GMT

Can you join in the database (SQL select .....) the fact table and the users table?

Re: Big table of users (efficient sql select)

Fri, 13 Nov 2015 10:45:27 GMT

Hi,

the fact table is created within qlikview. Getting it to sql again (or creating it in sql to begin with) would beat the purpose of what I am trying to achieve.

Thanks,

Nuno

Re: Big table of users (efficient sql select)

petter — Fri, 13 Nov 2015 10:51:24 GMT

How many distinct User-IDs do you have in your fact table?

Re: Big table of users (efficient sql select)

Fri, 13 Nov 2015 10:55:47 GMT

Around 200,000.

Re: Big table of users (efficient sql select)

petter — Fri, 13 Nov 2015 11:19:55 GMT

The only way I can see that is really efficient and still not very complicated is:

1) Create a table in your DB called FACT_USERID having one column UserID.

Make sure that you have indexes on the user id columns in the involved tables.

2) Load Script:

FACT_USERID:

LOAD DISTINCT

UserID

RESIDENT

FACT

ORDER BY

UserID

;

STORE FACT_USERID INTO FACT_USERID.CSV (txt);

DROP TABLE FACT_USERID;

EXECUTE cmd.exe /c cmd-file-to-execute-import-of-CSV-into-the-DB.cmd FACT_USERID.CSV;

// all popular SQL databases has some sort of command-line import tool to retrieve txt/csv-files ...

LEFT KEEP (FACT)

LOAD * ;

SQL

SELECT

FROM

Users

WHERE EXISTS( SELECT USER_ID FROM FACT_USERID);

Re: Big table of users (efficient sql select)

maxgro — Fri, 13 Nov 2015 11:36:28 GMT

you can build a dynamic sql where condition

T: Load

Pick(Ceil(6*Rand1),'a','b','c','d','e','f') as User,

Round(1000*Rand()*Rand()*Rand1) as Expression1;

Load Rand() as Rand1, IterNo() as TransLineID, RecNo() as TransID

Autogenerate 1000 While Rand()<=0.5 or IterNo()=1;

LOAD chr(39) & Concat( DISTINCT User , chr(39) & ',' & chr(39)) & chr(39) AS UserList

Resident T;

LET vUsers = Peek('UserList');

trace $(vUsers);

and then use in SQL

SQL select *

from Users

WHERE User IN ($(vUsers ));

but for 200k distinct users I think you can't build an efficient where clause;

example in Oracle a condition where user in (user1, user2, ....) will works only for 1000 users

You can try with an OR instead of IN

where (user = 'user1' or user = 'user2' ...............)

Maybe an option to load all the users in Qlik with an incremental load?