Specific attributes are different Product { id: sku: product dimensions: shipping weight: MSRP: price: description: ... artist: MxPx title: Panic release date: June 7, 2005 label: Side One Dummy track listing: [ The Darkest ... language: English format: CD ...
database heavily utilizes an Entity-Attribute-Value (EAV) data model. As is often the case, the cost of flexibility is complexity - Magento is no exception. The process of manipulating data in Magento is often more “involved” than that typically experienced using traditional relational tables.” - Varien EAV
All the disadvantages of a document store, but none of the advantages • Never should be used • One exception is Oracle XML which operates similar to a document store
• Allows for data integrity • Querying across attribute sets quite hard to do (lots of joins, OR statements and full table scanning) • New table needs to be created for each new attribute set
own table) • Likely best solution within the constraint of SQL • Supports data type enforcement • No data integrity enforcement • Easy querying across categories (for browse pages) since common data in single table • Every set needs a new table • Requires a ton of forsight, as changes are very complicated
to be fixed at the time of purchase • Embed them right in the order db.order.find( { 'items.sku': '00e8da9f' } ); db.order.find( { 'items.details.actor': 'James Stewart' } ).count();
} , { $inc : { y : 1 } } , false , true ); • // Isolated updates db.foo.update( { x : 1 , $atomic : 1 } , { $inc : { y : 1 } } , false , true ); • But there are caveats... • Despite the $atomic keyword, this is not an atomic update, since atomicity implies “all or nothing” • $atomic here means update is done without an interference from any other operation (isolated)
} , { $inc : { y : 1 } } , false , true ); • // Isolated updates db.foo.update( { x : 1 , $atomic : 1 } , { $inc : { y : 1 } } , false , true ); • But there are caveats... • Despite the $atomic keyword, this is not an atomic update, since atomicity implies “all or nothing” • $atomic here means update is done without an interference from any other operation (isolated) • An isolated update can only act on a single collection. Multi- collection updates are not transactional, thus not isolatable.
writes across multi-document transactions don't use Mongo • Many if not most e-commerce transactions could be accomplished within a single document write
writes across multi-document transactions don't use Mongo • Many if not most e-commerce transactions could be accomplished within a single document write • Unique indexes • This only works on keys used by the entire collection
writes across multi-document transactions don't use Mongo • Many if not most e-commerce transactions could be accomplished within a single document write • Unique indexes • This only works on keys used by the entire collection • Isolated (not atomic) single collection updates. • Mongo does not support locking • There are ways to work around this
writes across multi-document transactions don't use Mongo • Many if not most e-commerce transactions could be accomplished within a single document write • Unique indexes • This only works on keys used by the entire collection • Isolated (not atomic) single collection updates. • Mongo does not support locking • There are ways to work around this • It’s durable
example is straight from the documentation: > t = db.inventory > p = t.findOne({sku:'abc'}) > t.update({_id:p._id, qty:p.qty}, {'$inc': {qty: -1}}); > db.$cmd.findOne({getlasterror:1}); {"err" : , "updatedExisting" : true , "n" : 1 , "ok" : 1} // it worked
example is straight from the documentation: > t = db.inventory > p = t.findOne({sku:'abc'}) > t.update({_id:p._id, qty:p.qty}, {'$inc': {qty: -1}}); > db.$cmd.findOne({getlasterror:1}); {"err" : , "updatedExisting" : true , "n" : 1 , "ok" : 1} // it worked ... If that didn't work, try again until it does.
• Make your changes with the assertion that your product has the same state as it did when you last read it. • It is also possible to use OCC to bootstrap pessimistic concurrency and fake row level locking
shoes I just have to buy. 2. I call “dibs” (by grabbing them off the shelf). 3. I take them up to the cash register and purchase them: • Store inventory has been manually decremented. • I pay for them with my trusty AmEx. 4. If all goes according to plan, I walk out of the store. 5. If my card was declined, the shoes are “rolled back” ... out onto the shelves and sold to the next customer who wants them.
own document • Document consists of... • a reference to the SKU (product) • a state ( available / sold / ... ) • potentially other data (timestamp, order ref)
provide inventory hold in cart. > t = db.inventory > sku = sku.findOne({sku:'abc'}) > t.update({ref_id:sku._id, state: 'available'}, {'$set': {state: 'in cart'}}); > db.$cmd.findOne({getlasterror:1}); {"err" : , "updatedExisting" : true , "n" : 1 , "ok" : 1} // it worked just like reality, each item is either available, in a cart, or purchased
Product/Sellable • Address • Cart • CreditCard • Event • TaxRate • ... and then I got tired of typing them in • Just imagine this list has 40 more classes • ...
• Note how I said “effectively”? ... we cheat and persist our transient property to MongoDB as well • We can do this because we never really trust the value stored in Mongo
sorting and alerts, we can use the value stashed in MongoDB • It’s faster • It’s accurate enough • For financial transactions, we want the security and comfort of our RDBMS.
new product is created, its inventory is inserted in SQL • Every time an order is placed, inventory is verified and decremented • Whenever the SQL inventory changes, it is saved to MongoDB as well
and begin transaction 2. Check current product inventory 3. Decrement product inventory 4. Write the Order to SQL 5. Update affected MongoDB documents 6. Commit the transaction 7. Release product inventory lock
$id; /** @mongodb:String */ private $title; public function getId() { return $this->id; } public function getTitle() { return $this->title; } public function setTitle($title) { $this->title = $title; } }
{ // get the order entity $order = $eventArgs->getEntity(); // get odm reference to order.product_id $productId = $order->getProductId(); $product = $this->dm->getReference('MyBundle:Document\Product', $productId); // set the product on the order $em = $eventArgs->getEntityManager(); $productReflProp = $em->getClassMetadata('MyBundle:Entity\Order') ->reflClass->getProperty('product'); $productReflProp->setAccessible(true); $productReflProp->setValue($order, $product); } }
engineers, first wrote about this technique on his personal blog: http://jwage.com You can read the full article here: http://jwage.com/2010/08/25/blending-the- doctrine-orm-and-mongodb-odm/
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![db.products.find( { 'details.actor': { $all: ['James Stewart', 'Donna Reed'] }](https://files.speakerdeck.com/presentations/4e8126e72d853c0060001f97/slide_50.jpg){kind=link}
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