Class Transaction (2.15.1)

A transaction is a set of reads and writes that execute atomically at a single logical point in time across the columns/rows/tables in a database. Those reads and writes are grouped by passing them the same Transaction.

All reads/writes in the transaction must be executed within the same session, and that session may have only one transaction active at a time.

Spanner supports these transaction modes:

• ReadOnly. Provides guaranteed consistency across several reads, but does not allow writes. Can be configured to read at timestamps in the past. Does not need to be committed and does not take locks.
• ReadWrite. Supports reading and writing data at a single point in time. Uses pessimistic locking and, if necessary, two-phase commit. May abort, requiring the application to rerun.
• SingleUse. A restricted form of a ReadOnly transaction where Spanner chooses the read timestamp.