Записи с меткой mongo_note...

xoma Блог им. xoma 30 октября 2011 г., 20:12

By prepending a collection’s name with its containing database, you can get a fully qualified collection name called a namespace. For instance, if you are using the blog.posts collection in the cms database, the namespace of that collection would be
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xoma Блог им. xoma 30 октября 2011 г., 20:07

In addition to grouping documents by collection, MongoDB groups collections into databases. A single instance of MongoDB can host several databases, each of which can be thought of as completely independent. A database has its own permissions, and ea
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xoma Блог им. xoma 30 октября 2011 г., 19:40

Because any document can be put into any collection, the question often arises: “Why do we need separate collections at all?” It’s a good question—with no need for separate schemas for different kinds of documents, why should we use more than o
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xoma Блог им. xoma 30 октября 2011 г., 19:34

Collections are schema-free. This means that the documents within a single collection can have any number of different “shapes.” For example, both of the following documents could be stored in a single collection: {«greeting»: «Hello, world!»}
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xoma Блог им. xoma 30 октября 2011 г., 19:33

A collection is a group of documents. If a document is the MongoDB analog of a row in a relational database, then a collection can be thought of as the analog to a table.
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xoma Блог им. xoma 30 октября 2011 г., 19:32

MongoDB is type-sensitive and case-sensitive. For example, these documents are distinct: {«foo»: 3} {«foo»: «3»} As are as these: {«foo»: 3} {«Foo»: 3}
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xoma Блог им. xoma 30 октября 2011 г., 19:30

Values in documents are not just “blobs.” They can be one of several different data types (or even an entire embedded document—see “Embedded Documents” on page 20).
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xoma Блог им. xoma 30 октября 2011 г., 19:25

Some features common to relational databases are not present in MongoDB, notably joins and complex multirow transactions. These are architectural decisions to allow for scalability, because both of those features are difficult to provide efficiently
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