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up vote 1 down vote favorite

I'm using DynamoDb v2 interface for boto to make counter increments in my table. (I need v2 interface as I'll be dealing with indexes later on)

Somehow I'm not able to find how to do that without fetching item & updating it again.

Here is the code I'm using 

from boto.dynamodb2.table import Table
from boto.dynamodb2.items import Item

my_table = Table('my-table')

# Update counter for existing record.
data = {'key': 'my_key',
        'range_key': 'my_range',
       }

item = Item(my_table, data)
#### Do something here to increment 'counter' by 1
item.save()

What should I do to increment a 'counter' field??

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1 Answer

up vote 3 down vote

Check out this answer: Update DynamoDB Atomic Counter with Python / Boto

This is dealing with DynamoDB v1, and I have not tested if this still works with v2.

If you are already fetching the current value, it appears that 

item.add_attribute('counter', 1)
item.save()

will do an update_item request.

You can also do an update_item request directly:

dynoConnLayer1.update_item("my_table", 
                    {"key":{"S":"my_key"}, 'range_key' : {"S": "my_range"}},
                    {"counter":
                        {"Action":"ADD","Value":{"N":"1"}}
                    }
                )
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