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20.4.3 Documents and Collections

Contents

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20.4.3.1 Create, List, and Drop Collections
20.4.3.2 Working with Collections
20.4.3.3 Find Documents
20.4.3.4 Modify Documents
20.4.3.5 Remove Documents
20.4.3.6 Create and Drop Indexes

When you are using MySQL as a Document Store, collections are containers within a schema that you can create, list, and drop. Collections contain JSON documents that you can add, find, update, and remove.

The examples in this section use the countryinfo collection in the world_x schema. For instructions on setting up the world_x schema, see Section 20.4.2, “Download and Import world_x Database”.

Documents

In MySQL, documents are represented as JSON objects. Internally, they are stored in an efficient binary format that enables fast lookups and updates.

  • Simple document format for Python: 

    {"field1": "value", "field2" : 10, "field 3": null}

An array of documents consists of a set of documents separated by commas and enclosed within [ and ] characters.

  • Simple array of documents for Python: 

    [{"Name": "Aruba", "_id": "ABW"}, {"Name": "Angola", "_id": "AGO"}]

MySQL supports the following Python value types in JSON documents:

  • numbers (integer and floating point)

  • strings

  • boolean (False and True)

  • None

  • arrays of more JSON values

  • nested (or embedded) objects of more JSON values

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Collections

Collections are containers for documents that share a purpose and possibly share one or more indexes. Each collection has a unique name and exists within a single schema.

The term schema is equivalent to a database, which means a group of database objects as opposed to a relational schema, used to enforce structure and constraints over data. A schema does not enforce conformity on the documents in a collection.

In this quick-start guide:

  • Basic objects include:

    Object form Description
    db db is a global variable assigned to the current active schema. When you want to run operations against the schema, for example to retrieve a collection, you use methods available for the db variable.
    db.get_collections() db.get_collections() holds a list of collections in the schema. Use the list to get references to collection objects, iterate over them, and so on.

  • Basic operations scoped by collections include:

    Operation form Description
    db.name.add() The add() method inserts one document or a list of documents into the named collection.
    db.name.find() The find() method returns some or all documents in the named collection.
    db.name.modify() The modify() method updates documents in the named collection.
    db.name.remove() The remove() method deletes one document or a list of documents from the named collection.

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Document created the 26/06/2006, last modified the 26/10/2018
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References

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