$isolated¶

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Definition
Behavior
Example

Definition¶

$isolated¶

Prevents a write operation that affects multiple documents from yielding to other reads or writes once the first document is written. By using the $isolated option, you can ensure that no client sees the changes until the operation completes or errors out.

This behavior can significantly affect the concurrency of the system as the operation holds the write lock much longer than normal for storage engines that take a write lock (e.g. MMAPv1), or for document-level locking storage engine that normally do not take a write lock (e.g. WiredTiger), $isolated operator will make WiredTiger single-threaded for the duration of the operation.

Behavior¶

The $isolated isolation operator does not provide “all-or-nothing” atomicity for write operations.

$isolated does not work with sharded clusters.

Example¶

Consider the following example:

db.foo.update(
    { status : "A" , $isolated : 1 },
    { $inc : { count : 1 } },
    { multi: true }
)

Without the $isolated operator, the multi-update operation will allow other operations to interleave with its update of the matched documents.

参见

db.collection.update() and db.collection.remove()

$atomic¶: 2.2 版后已移除: The $isolated operator replaces $atomic.

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