Querying AWS DynamoDB using Ruby

Question

I have inherited a DynamoDB table with three columns of which one is a key

 Id - String - hashKey
 ProductID - String
 UsageCount - number

I want to run a query/scan that logically equates to the following

 select ProductID, UsageCount where ProductID='abcd'

Although ProductID is not a key of any sort, I can use the AmazonDynamoDB console and add a filter

and get just what I want. So I assume I should be able to do the same thing with code (although everyone talks about using hash and range keys for such purposes)

I am trying to do the same thing with RUBY but not getting results...

 resp = $dynamodb.scan(
       :table_name => PRODUCTTABLE,
       :projection_expression => "Id, TenantId, SeatCount",
          :filter_expression => 'TenantId = abcd'
                       )

Could someone help me with the correct syntax for doing this? I tried numerous variations that all throw exceptions except for the above syntax that does not throw an exception but returns zero rows. So Im thinking it must be close :) (or maybe not)

Chen Harel · Accepted Answer · 2015-11-10 23:17:40Z

2

You have to use both filter_expression but make it 'TenantId = :val'

and then pass :val with expression_attribute_names and expression_attribute_values

Even though it's in Java, this doc will help clear things out for you

answered Nov 10, 2015 at 23:17

Chen Harel

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1 Comment

user1813603 Over a year ago

thx! - the following syntax worked...

resp = $dynamodb.scan(       :table_name => "MyTable",       :limit => 2,       :projection_expression => "Id, DataSource, TenantId",       :filter_expression => 'TenantId = :val',       :expression_attribute_values => { ":val" => '6e874f58-ac9a-44ae-9ed4-9ed2e8828800' } )

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