This gives DBAs and developers finer surgical indexing capabilities to support a wide range of schema and query scenarios. The most important concept to remember when dealing with arrays in MongoDB is to know that whenever we target a particular array element (a comment in this case). MongoDB’s support for this and other interesting indexing strategies is pretty phenomenal. This index will be smaller than one on a whole array and will be a non-multiKey one, reducing the work the server has to do to process your query. If your query targets a specific known positional array element, this indexing strategy can buy you a performance boost. MongoDB Compass is free and supported by the MongoDB team, but there are many alternatives depending on your requirements. The positional index we created doesn’t include pointers based on all elements, so it would be “missing” documents if mongo was to use the positional index for this query. Most admin tools use the MongoDB API for broader cross-version compatibility. It is not correct to use the positional array index because the general query above asks are there any elements in the array with sku “abc”. However, in more complex scenarios in which types cannot be implicitly reflected (for example, arrays or nested object structures), types must be indicated. The path used in the query above did not target the first positional element in the array, and therefore the query planner chose a full collection scan "COLLSCAN". The schema for the things collection might look like this: ).explain() When a customer buys a “product” they are actually buying a box of items - a list of parts where the first one is by convention the “widget” and the rest are the parts of that widget. Each widget is made of parts - each of which can be also sold separately. The validation editor supports JSON Schema validation, and validation with query expressions using query operators.As you edit your validation, Compass updates in real-time to display a document from your collection that passes the validation and a document that fails. What is that good for you ask? Consider the following scenario: This feature can help you create more efficient indexes for specific scenarios. Did you know that MongoDB lets you index a specific positional element in an array? Well, it does! I stumbled across this feature when reading the source code for mongod for an unrelated feature exploration, and stumbled upon this great feature.
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