Mix in action

example.sql

CREATE TABLE Publisher
(
  id            text AUTO, -- auto-generated, uuid
  stacks        set of text REFERENCES Stacks, -- primary key ref
  sub_count     int, -- Subscription.stack.publisher.id
  PRIMARY KEY   (id)
);

CREATE TABLE Stack 
(
  id              text AUTO,
  publisher       text NOT NULL REFERENCES Publisher,
  subscriptions   set of text REFERENCES Subscription,
  PRIMARY KEY     (id)
);

CREATE TABLE Subscription
(
  id              text AUTO,
  user            text NOT NULL REFERENCES User,
  stack           text NOT NULL REFERENCES Stack,
  notify_freq     text NOT NULL,
  language        text NOT NULL,
  last_notified   int,
  primary key     (id)
);

CREATE TABLE NewDocs
(
  stack           text NOT NULL REFERENCES Stack,
  add_date        int NOT NULL,
  doc_id          text NOT NULL,
  PRIMARY KEY     (stack),
  SECONDARY KEY   (add_date)  
);

CREATE TABLE User 
(
  id              text NOT NULL,
  subscriptions   set of text REFERENCES Subscription,
  PRIMARY KEY     (id)
);

CREATE TABLE UnconfirmedEmails
(
  id            text AUTO,
  email         text NOT NULL,       
  PRIMARY KEY   (id)    
);


-- CREATE TRIGGER reminder2
-- ON Sales.Customer
-- AFTER INSERT, UPDATE, DELETE 
-- AS

publisher.erl

-module(publisher).

-export([
    setup/2, 
    teardown/0, 
    describe/0, 
    create/1, 
    delete/1, 
    fetch/1, 
    store/2, 
    add_to_stacks/2, 
    remove_from_stacks/2, 
    bump_sub_count/2
    ]).

setup(RPS, WPS) ->
    ddb:create_table(<<"Publisher">>, RPS, WPS).

teardown() ->
    ddb:remove_table(<<"Publisher">>).

describe() ->
    ddb:describe_table(<<"Publisher">>).

create(Values) ->
    Values1 = mix:auto_gen(Values, [ {<<"id">>, 'string'} ]),
    Args = mix:prep_ddb_args(Values1, [
        {<<"id">>, 'string'}, 
        {<<"sub_count">>, 'number'}, 
        {<<"stacks">>, 'string_set'}
    ]),
    ddb:put(<<"Publisher">>, Args).

delete(Id) ->
    ddb:delete(<<"Publisher">>, ddb:key_value(Id, 'string')).

fetch(Id) ->
    ddb:get(<<"Publisher">>, ddb:key_value(Id, 'string')).

store(Id, Values) ->
    Args = mix:prep_ddb_args(Values, 'put', [
        {<<"sub_count">>, 'number'}, 
        {<<"stacks">>, 'string_set'}
    ]),
    ddb:update(<<"Publisher">>, ddb:key_value(Id, 'string'), Args).

add_to_stacks(Id, Values) ->
    ddb:update(<<"Publisher">>, ddb:key_value(Id, 'string'), [{<<"stacks">>, Values, 'string_set', 'add'}]).

remove_from_stacks(Id, Values) ->
    ddb:update(<<"Publisher">>, ddb:key_value(Id, 'string'), [{<<"stacks">>, Values, 'string_set', 'delete'}]).

bump_sub_count(Id, Value) ->
    ddb:update(<<"Publisher">>, ddb:key_value(Id, 'string'), [{<<"sub_count">>, Value, 'number', 'add'}]).

stack.erl

-module(stack).

-export([
    setup/2, 
    teardown/0, 
    describe/0, 
    create/1, 
    delete/1, 
    fetch/1, 
    store/2, 
    add_to_subscriptions/2, 
    remove_from_subscriptions/2
    ]).

setup(RPS, WPS) ->
    ddb:create_table(<<"Stack">>, RPS, WPS).

teardown() ->
    ddb:remove_table(<<"Stack">>).

describe() ->
    ddb:describe_table(<<"Stack">>).

create(Values) ->
    Values1 = mix:auto_gen(Values, [ {<<"id">>, 'string'} ]),
    Args = mix:prep_ddb_args(Values1, [
        {<<"id">>, 'string'}, 
        {<<"subscriptions">>, 'string_set'}, 
        {<<"publisher">>, 'string'}
    ]),
    ddb:put(<<"Stack">>, Args),
    PrimaryKey = proplists:get_value(<<"id">>, Values1),
    publisher:add_to_stacks(Id, [PrimaryKey]).

delete(Id) ->
    ddb:delete(<<"Stack">>, ddb:key_value(Id, 'string')),
    PrimaryKey = proplists:get_value(<<"id">>, Values1),
    publisher:remove_from_stacks(Id, [PrimaryKey]).

fetch(Id) ->
    ddb:get(<<"Stack">>, ddb:key_value(Id, 'string')).

store(Id, Values) ->
    Args = mix:prep_ddb_args(Values, 'put', [
        {<<"subscriptions">>, 'string_set'}, 
        {<<"publisher">>, 'string'}
    ]),
    ddb:update(<<"Stack">>, ddb:key_value(Id, 'string'), Args).

add_to_subscriptions(Id, Values) ->
    ddb:update(<<"Stack">>, ddb:key_value(Id, 'string'), [{<<"subscriptions">>, Values, 'string_set', 'add'}]).

remove_from_subscriptions(Id, Values) ->
    ddb:update(<<"Stack">>, ddb:key_value(Id, 'string'), [{<<"subscriptions">>, Values, 'string_set', 'delete'}]).

subscription.erl

-module(subscription).

-export([
    setup/2, 
    teardown/0, 
    describe/0, 
    create/1, 
    delete/1, 
    fetch/1, 
    store/2, 
    bump_last_notified/2
    ]).

setup(RPS, WPS) ->
    ddb:create_table(<<"Subscription">>, RPS, WPS).

teardown() ->
    ddb:remove_table(<<"Subscription">>).

describe() ->
    ddb:describe_table(<<"Subscription">>).

create(Values) ->
    Values1 = mix:auto_gen(Values, [ {<<"id">>, 'string'} ]),
    Args = mix:prep_ddb_args(Values1, [
        {<<"id">>, 'string'}, 
        {<<"last_notified">>, 'number'}, 
        {<<"language">>, 'string'}, 
        {<<"notify_freq">>, 'string'}, 
        {<<"stack">>, 'string'}, 
        {<<"user">>, 'string'}
    ]),
    ddb:put(<<"Subscription">>, Args),
    PrimaryKey = proplists:get_value(<<"id">>, Values1),
    user:add_to_subscriptions(Id, [PrimaryKey]),
    stack:add_to_subscriptions(Id, [PrimaryKey]).

delete(Id) ->
    ddb:delete(<<"Subscription">>, ddb:key_value(Id, 'string')),
    PrimaryKey = proplists:get_value(<<"id">>, Values1),
    user:remove_from_subscriptions(Id, [PrimaryKey]),
    stack:remove_from_subscriptions(Id, [PrimaryKey]).

fetch(Id) ->
    ddb:get(<<"Subscription">>, ddb:key_value(Id, 'string')).

store(Id, Values) ->
    Args = mix:prep_ddb_args(Values, 'put', [
        {<<"last_notified">>, 'number'}, 
        {<<"language">>, 'string'}, 
        {<<"notify_freq">>, 'string'}, 
        {<<"stack">>, 'string'}, 
        {<<"user">>, 'string'}
    ]),
    ddb:update(<<"Subscription">>, ddb:key_value(Id, 'string'), Args).

bump_last_notified(Id, Value) ->
    ddb:update(<<"Subscription">>, ddb:key_value(Id, 'string'), [{<<"last_notified">>, Value, 'number', 'add'}]).

Note that Amazon DynamoDB has no built-in referential integrity so I generate the code for it. For example, the code in subscription:create updates both User and Publisher "tables".