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- Read Concern
"snapshot"
-
"snapshot"
¶
Read Concern "snapshot"
¶
New in version 4.0.
Read concern "snapshot"
is only available for multi-document
transactions.
- If the transaction is not part of a causally consistent session, upon transaction commit with write concern
"majority"
, the transaction operations are guaranteed to have read from a snapshot of majority-committed data. - If the transaction is part of a causally consistent session, upon transaction commit with write concern
"majority"
, the transaction operations are guaranteed to have read from a snapshot of majority-committed data that provides causal consistency with the operation immediately preceding the transaction start.
Read Concern and Transactions¶
Multi-document transactions support read concern
"snapshot"
as well as "local"
, and
"majority"
.
Note
You set the read concern at the transaction level, not at the individual operation level. To set the read concern for transactions, see Read Concern/Write Concern/Read Preference.
For a list of all operations that accept read concerns, see Operations That Support Read Concern.
Causally Consistent Sessions¶
snapshot
is available for transactions that are part of
a causally consistent session.