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Accessing Amazon DynamoDB

Authenticating

ddb_iam:credentials("access key", "secret").
{'ok', Key, Secret, Token} = ddb_iam:token(129600).
ddb:credentials(Key, Secret, Token).

Creating a table with a hash key

ddb:create(<<"foo">>, ddb:key_type(<<"hashkey">>, 'string'), 10, 10).

Creating a table with hash and range keys

ddb:create(<<"bar">>, ddb:key_type(<<"hashkey">>, 'string', <<"rangekey">>, 'number'), 10, 10).

Adding a record to a table with a hash key

ddb:put(<<"foo">>, [{<<"hashkey">>, <<"hash key value">>, 'string'},
                    {<<"field1">>, <<"string value">>, 'string'}, 
                    {<<"field2">>, <<"100">>, 'number'}]).

Adding a record to a table with hash and range keys

ddb:put(<<"bar">>, [{<<"hashkey">>, <<"hash key value">>, 'string'},
                    {<<"rangekey">>, <<"1000">>, 'number'},
                    {<<"field1">>, <<"string value">>, 'string'}, 
                    {<<"field2">>, <<"100">>, 'number'}]).

ddb:put(<<"bar">>, [{<<"hashkey">>, <<"hash key value">>, 'string'},
                    {<<"rangekey">>, <<"2000">>, 'number'},
                    {<<"field3">>, <<"string value">>, 'string'}]).

Fetching a record from a table using a hash key

ddb:get(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string')).

Fetching a record from a table using hash and range keys

ddb:get(<<"bar">>, ddb:key_value(<<"hash key value">>, 'string', <<"1000">>, 'number')).

Querying a table

ddb:find(<<"bar">>, {<<"hash key value">>, 'string'}, {'between', 'number', [<<"1000">>, <<"2000">>]}).

Changing value (and type) of one field while deleting another

ddb:update(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string'), 
                      [{<<"field1">>, <<"1">>, 'number', 'put'},
                       {<<"field2">>, 'delete'}]).

Adding to a string set field and returning pre-update values of updated fields

ddb:update(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string'), 
                      [{<<"field2">>, [<<"1">>, <<"2">>], 'string_set', 'add'}],
                      'updated_old').

Deleting an item from a string set field and returning the values of all fields before the update

ddb:update(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string'), 
                      [{<<"field2">>, [<<"1">>], 'string_set', 'delete'}],
                      'all_old').

Update field1 only when field2 does not exist

ddb:cond_update(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string'), 
                           [{<<"field1">>, <<"1">>, 'number', 'put'}],
                           {'does_not_exist', <<"field2">>}).

Update field1 only when field2 exists and has a numerical value of 1

ddb:cond_update(<<"foo">>, ddb:key_value(<<"hash key value">>, 'string'), 
                           [{<<"field1">>, <<"1">>, 'number', 'put'}],
                           {'exists', <<"field2">>, <<"1">>, 'number'}).

See src/ddb.erl for the rest of the API.

Note that dates in Dynamo are represented as seconds since Unix epoch!

All data is stored as strings but you have to specify whether each field is a string or a number.

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