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    <p>First let's fix the model a bit. In your schema you have more attributes per dimension: id and name, you might end up having more details in the future. You can add them by specifying attributes as a list: <code>"attriubtes": ["id", "name"]</code>. Note also that the dimension is named as entity <code>product</code> not as a key <code>id_product</code>. The key <code>id_product</code> is just an attribute of the <code>product</code> dimension, as is <code>name</code> or in the future maybe <code>category</code>. Dimension reflects analysts point of view.</p> <p>For the time being, we ignore the fact that date should be a special dimension and consider date as single-value key, for example a year, not to make things complicated here.</p> <pre class="lang-js prettyprint-override"><code>"dimensions": [ {"name": "user", "attributes": ["id", "name"]}, {"name": "product", "attributes": ["id", "name"]}, {"name": "date"} ], </code></pre> <p>Because we changed names of the dimensions, we have to change them in the cube's dimension list:</p> <pre class="lang-js prettyprint-override"><code>"cubes": [ { "name": "purchases", "dimensions": ["user", "product", "date"], ... </code></pre> <p>Your schema reflects classic transactional schema, not traditional data warehouse schema. In this case, you have to be explicit, as you were, and mention all necessary mappings. The rule is: if the attribute belongs to a fact table (logical view), then the key is just <code>attribute</code>, such as <code>price</code>, no table specification. If the attribute belongs to a dimension, such as <code>product.id</code>, then the syntax is <code>dimension.attribute</code>. The value of the mappings dictionary is physical table and physical column. See <a href="http://packages.python.org/cubes/mapping.html#mapping">more information about mappings</a>. Mappings for your schema look like:</p> <pre class="lang-js prettyprint-override"><code>"mappings": { "price": "products.price", "product.id": "products.id", "product.name": "products.name", "user.id": "users.id", "user.name": "users.name" } </code></pre> <p>You would not have to write mappings if your schema was:</p> <pre><code>fact purchases id | date | user_id | product_id | amount dimension product id | name | price dimension user id | name </code></pre> <p>In this case you will need only joins, because all dimension attributes are in their respective dimension tables. Note the <code>amount</code> in the fact table, which in your case, as you do not have <code>count</code> of purchased products per purchase, would be the same as <code>price</code> in <code>product</code>.</p> <p>Here is the updated model for your model:</p> <pre class="lang-js prettyprint-override"><code>{ "dimensions": [ {"name": "user", "attributes": ["id", "name"]}, {"name": "product", "attributes": ["id", "name"]}, {"name": "date"} ], "cubes": [ { "name": "purchases", "dimensions": ["user", "product", "date"], "measures": ["price"], "mappings": { "price": "products.price", "product.id": "products.id", "product.name": "products.name", "user.id": "users.id", "user.name": "users.name" }, "joins": [ { "master": "purchases.user_id", "detail": "users.id" }, { "master": "purchases.product_id", "detail": "products.id" } ] } ] } </code></pre> <p>You can try the model without writing any Python code, just by using the <a href="http://packages.python.org/cubes/slicer.html"><code>slicer</code></a> command. For that you will need <code>slicer.ini</code> <a href="http://packages.python.org/cubes/server.html#configuration">configuration file</a>:</p> <pre><code>[server] backend: sql port: 5000 log_level: info prettyprint: yes [workspace] url: sqlite:///data.sqlite [model] path: model.json </code></pre> <p>Change <code>url</code> in <code>[workspace]</code> to point to your database and change <code>path</code> in <code>[model]</code> to point to your model file. Now you can try:</p> <pre><code>curl "http://localhost:5000/aggregate" </code></pre> <p>Also try to drill-down:</p> <pre><code>curl "http://localhost:5000/aggregate?drilldown=product" </code></pre> <p>If you need any further help, just let me know, I'm the Cubes author.</p>
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    1. COThanks, great walkthrough!
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