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Why do unlinked tables consume excessive memory?

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!

1 Solution

Accepted Solutions
Anonymous
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Author

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

View solution in original post

7 Replies
Anonymous
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Author

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.

Not applicable
Author

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!

Anonymous
Not applicable
Author

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

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

Not applicable
Author

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"?

Anonymous
Not applicable
Author

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

Anonymous
Not applicable
Author

Have a look at this sample qvw.

You see one Straight Table Object with a Proper Join.

And another with a Cartesian Join.

Not applicable
Author

I must have inadvertently included fields from two different tables.

Eternally appreciative,

Will