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Anonymous
Not applicable

Memory size of copied table

If I copy a table (using ProjectData-DAX = 'ProjectData'), the resulting table is way bigger in terms of memory size than the original table. Why is this?

Screenshot VertiPaq AnalyzerScreenshot VertiPaq Analyzer

 

 

Thanks in advance for your hints!

1 ACCEPTED SOLUTION
AntrikshSharma
Super User
Super User

@Anonymous  That's because SSAS uses sorting to reduce the size of the table, before loading the data into the model SSAS will find the best columns that will help in reducing how frequently the value changes, so if you have a column that has TRUE/FALSE and if that column is used first in the sort order, it will split the whole table into 2 chunks and the value will change only once, after that other columns will be used for sorting. 

 

Once you load the data using DAX, the sorting doesn't occur but the columns are still compressed, so that's why the size of the table created with DAX can be biger.

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1 REPLY 1
AntrikshSharma
Super User
Super User

@Anonymous  That's because SSAS uses sorting to reduce the size of the table, before loading the data into the model SSAS will find the best columns that will help in reducing how frequently the value changes, so if you have a column that has TRUE/FALSE and if that column is used first in the sort order, it will split the whole table into 2 chunks and the value will change only once, after that other columns will be used for sorting. 

 

Once you load the data using DAX, the sorting doesn't occur but the columns are still compressed, so that's why the size of the table created with DAX can be biger.

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