Data Masking and Subsetting - Generating an Subset export

I’m new to Data Masking and Subsetting. My first attempt is to generate an export file with only subsetting, no masking. 

I created an Application Data Model for a single schema. Then I created a Data Subsetting Definition. In Table Rules I added a WHERE clause 

to limit a single parent table to the most recent 90 days of data, and by relationships it’s 15 child tables would also be limited. 

The Generating a Subset step ran for 2.6 days before erroring out due to running out of process memory. 

From the log it looks like the process was gathering all the rowids from those 16 tables.