ValidateSnapshotReadTS strictly validates that readTS does not exceed the PD timestamp.

Initing is the key for indicating if the server is running bootstrap or upgrade job.

LastExecuteDDL is the key for whether the session execute a ddl command last time.

QueryString is the key for original query string.

Context is an interface for transaction and executive args environment.

InstancePlanCache represents the instance/node level plan cache.

SessionPlanCache is an interface for prepare and non-prepared plan cache.

SessionStatesHandler is an interface for encoding and decoding session states.

TxnFuture is an interface where implementations have a kv.Transaction field and after calling Wait of the TxnFuture, the kv.Transaction will become valid.