April 2020
Beginner to intermediate
540 pages
14h 14m
Russian
Content preview from MongoDB: полное руководство
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150 Глава 5. Индексы
этому MongoDB может потребоваться выполнить дедупликацию, прежде
чем вернуть результаты.
Кардинальность индекса
Под кардинальностью понимается количество различных значений
для поля в коллекции. Некоторые поля, такие как "gender" или "newsletter
opt-out", могут иметь только два возможных значения, что считается очень
низкой кардинальностью. Другие поля, такие как "username" или "email", мо-
гут иметь уникальное значение для каждого документа в коллекции, что
является высокой кардинальностью. Третьи находятся где-то посередине,
например "age" или "zip code".
В целом чем больше кардинальность поля, тем полезнее может ...
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