SNAPSHOTREAD

Enables or disables snapshot read mode for the current session.

Syntax

SNAPSHOTREAD <ON | OFF>

Parameters

Parameter	Required	Description
ON	Yes (one of)	Enables snapshot read mode on the session.
OFF	Yes (one of)	Disables snapshot read mode on the session.

Exactly one of ON or OFF must be provided. The argument is case-insensitive.

Return Value

Simple string: OK on success.

Behavior

The command sets or clears snapshot read mode on the current session. When enabled, subsequent FoundationDB reads performed by the session use snapshot isolation instead of the default serializable isolation.

Snapshot reads do not create read conflict ranges, which means they will not cause transactions to conflict with concurrent writes to the same keys. This is useful for long-running reads or read-heavy workloads where strict serializability is not required, and reducing transaction conflicts is more important than guaranteeing a perfectly consistent view.

The setting is session-scoped. It persists until explicitly changed or the session ends. It can be toggled at any time, regardless of whether a transaction is currently active.

Supported Commands

The following commands honor the SNAPSHOTREAD setting:

Command	Honors SNAPSHOTREAD
ZGET	Yes
ZGETI64	Yes
ZGETF64	Yes
ZGETD128	Yes
ZGETRANGE	Yes
ZGETKEY	Yes
ZGETRANGESIZE	Yes
BUCKET.QUERY	Yes
BUCKET.INSERT	No, always uses serializable reads
BUCKET.DELETE	No, always uses serializable reads
BUCKET.UPDATE	No, always uses serializable reads

Mutation commands (BUCKET.INSERT, BUCKET.DELETE, BUCKET.UPDATE) always use serializable reads regardless of the SNAPSHOTREAD setting.

Errors

Error Code	Description
ERR	illegal argument for SNAPSHOTREAD: '<value>': The argument is neither ON nor OFF.

Examples

Enable snapshot read mode:

> SNAPSHOTREAD ON
OK

Disable snapshot read mode:

> SNAPSHOTREAD OFF
OK

Invalid argument:

> SNAPSHOTREAD MAYBE
(error) ERR illegal argument for SNAPSHOTREAD: 'MAYBE'