topic Re: Why do unlinked tables consume excessive memory? in QlikView

Why do unlinked tables consume excessive memory?

Tue, 06 Oct 2015 14:20:52 GMT

I have three tables. They load into QV as chart objects and they consume a lot of memory "Out of Object Memory" and very unresponsive.

I rename some fields, they all link up, and the memory consumption issue is fixed.

Why does this occur?

When the tables are linked I see more records than I should, my count (field) is higher than the number of records in the table.

I am trying to troubleshoot this behavior and fixed it by breaking the table links but the program becomes unusable due to memory usage.

Thanks!

Re: Why do unlinked tables consume excessive memory?

Anonymous — Tue, 06 Oct 2015 14:57:13 GMT

If 2 tables are not linked in the Data Model, but are both on a front end charts then QlikView at the front end will do a Cartesian join resulting in Chart Rows = (Number of rows in Table1) * (Number of rows in Table2), which could result in loads and loads of rows.

Moral of the story: Always make sure you tables are joined properly in the Data Model.

Re: Why do unlinked tables consume excessive memory?

Tue, 06 Oct 2015 15:07:01 GMT

Why is it attempting to join them if they don't have the same field names?

Is it impossible to have a stand-alone table?

Thank you very much!

Re: Why do unlinked tables consume excessive memory?

Anonymous — Tue, 06 Oct 2015 20:13:44 GMT

When you have no common fields that is what a Cartesian Join is.

http://c2.com/cgi/wiki?CartesianJoin

Re: Why do unlinked tables consume excessive memory?

Wed, 07 Oct 2015 12:28:35 GMT

I understand - and appreciate your continued patience with me.

I suppose I had to come to appreciate that QlikView won't allow a table to remain unlinked and will try to force it into the data model if no explicit links are created. It won't just "leave it alone".

Edit:

I thought I could have a "Data Island"?

Re: Why do unlinked tables consume excessive memory?

Anonymous — Wed, 07 Oct 2015 14:30:10 GMT

You can have Data Islands and sometimes they can be most useful, often exploited by some cunning Set analysis

But if in a front end object you reference fields from 2 seperate data tables unlinked in the Data Model [without cunning Set Analysis] then that causes the Cartesian join in the front end object

Re: Why do unlinked tables consume excessive memory?

Anonymous — Wed, 07 Oct 2015 14:46:27 GMT

Have a look at this sample qvw.

You see one Straight Table Object with a Proper Join.

And another with a Cartesian Join.

Re: Why do unlinked tables consume excessive memory?

Thu, 08 Oct 2015 13:21:36 GMT

I must have inadvertently included fields from two different tables.

Eternally appreciative,

Will