Load Performance

[anupamsri27]

Hi,

I have a question on data load performance:

which is fast...loading all data using "*" or to write all the columns one by one.

Thanks,

[Or]

Pretty sure there wouldn't be any difference, but you can test this easily enough if you have a large dataset.

[novolouy · Accepted solution]

Hi!

We tested this some time back.
You only notice the difference when the data you are loading is very large, many hundred thousands of lines and many fields.

It is more performant when you specify the fields instead of doing a Load *.
This is because Qlikview does not have to first check how many fields are available on the source, it already knows and loads those specified fields.

But again, only noticeable when large data sources are being loaded.
In my case when the source is less than 20 fields and less than 500.000 lines, I use a Load *, otherwise I specify the fields.

Hope this answers your question!

[marcus_sommer]

In many cases you don't need all fields/records and if you would load only necessary data you will of course save resources. Further often you don't need to write everything because this could do the wizard - you may drop the not wanted fields within the wizard or just delete it afterwards in the script.

- Marcus

[basav]

Totally agree with @marcus_sommer  

Just today I had a application with all the rows of the tables loaded, App size was around  1 GB, and the app performance was obviously slow. When looked at the field, unused were consuming more space than the used, so I dropped the unused fields ( brought down my app size to 250MB, and the performance was better)

In terms of load performance, It is best to not use "where" clause directly on the data source, being loaded at first, always convert large excel files to qvd which will help load the table faster and improve the performance.