Data loader fails with Operation aborted

[Erik]

Im getting an error when running Data Loader with my MongoDB Atlas connection. 

Last 2 lines from logs: 

• $Syn 37 = $Syn 19+$Syn 24+$Syn 25+$Syn 26

• Operation aborted

Below is the full logs

....
table_xx << QueryResult
Lines fetched: 2,229
table_xx << QueryResult
Lines fetched: 1,246
table_xx << QueryResult
Lines fetched: 641
$Syn 1 = _id+table_xx
....
$Syn 34 = $Syn 21+$Syn 28+$Syn 29+$Syn 30
$Syn 35 = $Syn 20+$Syn 25+$Syn 27
$Syn 36 = $Syn 20+$Syn 21+$Syn 22
$Syn 37 = $Syn 19+$Syn 24+$Syn 25+$Syn 26
Operation aborted

Im not sure what is happening and what can we do ?

[Vegar]

You have a lot of sythetic keys. You should probably take a look at them. Synthetic keys may cause a big unwantwd increase in Memory and CPU usage. Unsufficient RAM and CPU are probably  the cause  of the issue you are experiencing. 

https://help.qlik.com/en-US/sense/February2023/Subsystems/Hub/Content/Sense_Hub/Scripting/synthetic-...

[Vegar]

You could also take a look at @hic 's old blog post about Synthetic Keys in order to understand them better. It is from 2013, but still good.

Synthetic Keys by Henric Cronström 

[Erik]

Thanks a lot for the response,

I may be confused,  but I dont create any keys as QLIK created them from my existing MongoDB database. 

Is there a way to stop this behaviour and not generate Synthetic Keys ?

[Or]

Keys are automatically created when your data structure contains fields with identical names in different tables. I'd also suggest reading the links posted by Vegar to understand more about how and why this works, and how to deal with it if it isn't intended.