InitialSnapshot¶

InitialSnapshot is an initial Snapshot of a delta table (at the logPath) that is about to be created (so there is no delta log yet).

InitialSnapshot is a Snapshot with the following:

Snapshot	Value
LogSegment	Empty transaction log directory (for the logPath)
minFileRetentionTimestamp	-1
minSetTransactionRetentionTimestamp	(undefined)
Path	logPath
Timestamp	-1
Version	-1
VersionChecksum	(undefined)

Creating Instance¶

InitialSnapshot takes the following to be created:

Path (Apache Hadoop) of the Transaction Log
DeltaLog
Metadata

InitialSnapshot is created when:

SnapshotManagement is requested to createSnapshotAtInitInternal and installLogSegmentInternal
ConvertToDeltaCommandBase is requested to createDeltaActions

Metadata¶

InitialSnapshot can be given a Metadata when created. Unless given, InitialSnapshot creates a Metadata with the following:

Metadata	Value
configuration	mergeGlobalConfigs
createdTime	Current time (in ms)

computedState¶

Signature

computedState: Snapshot.State

computedState is part of the Snapshot abstraction.

computedState initialState.

Lazy Value

computedState is a Scala lazy value to guarantee that the code to initialize it is executed once only (when accessed for the first time) and the computed value never changes afterwards.

Learn more in the Scala Language Specification.

Question

Why does InitialSnapshot define the private initialState to initialize computedState? They could be one, couldn't they?

Initial State¶

initialState: Snapshot.State

initialState...FIXME