If you use form 

INSERT ... ['A']

INSERT ... ['B']

latest INSERT will overwrite first, because this insert the whole list. It's 
better to use UPDATE like:

UPDATE ... SET events = events + ['A']

UPDATE ... SET events = events + ['B']

These operations add new elements to the end of existing list.

>From here https://docs.datastax.com/en/cql/3.0/cql/cql_using/use_list_t.html :

These update operations are implemented internally without any 
read-before-write. Appending and prepending a new element to the list writes 
only the new element.

Best regards, Vladimir Yudovin, 

Winguzone - Hosted Cloud Cassandra on Azure and SoftLayer.
Launch your cluster in minutes.

---- On Wed, 12 Oct 2016 17:39:46 -0400Aoi Kadoya <cadyan....@gmail.com> 
wrote ----



When inserting different data into a list type column from different 

clients at the same time, is data supposed to be combined into one 



For example, if these 2 queries were requested from clients at the 

same timing, how events list should look like after? 


INSERT INTO cycling.upcoming_calendar (year, month, events) VALUES 

(2015, 06, ['A']); 

INSERT INTO cycling.upcoming_calendar (year, month, events) VALUES 

(2015, 06, ['B']); 


In my understanding, each operation should be treated as atomic, which 

makes me think that even if client throw the queries at the same time, 

cassandra would take them separately and the last insert would update 

the events list. (= data should be either ['A'] or ['B']) 


In my environment, I found that some data was saved as like ['A',B'] 

in the case like above. 

Is this expected behavior of list data type? 


I am still new to cassandra and trying to make myself understood how 

this happened. 

Appreciate if you could help me with figuring this out! 




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