manifest: minor cleanup of init backing methods

Author: RaduBerinde

compaction.go

@@ -2593,7 +2593,7 @@ func (d *DB) runCopyCompaction(
 	if objMeta.IsExternal() {
 		// external -> local/shared copy. File must be virtual.
 		// We will update this size later after we produce the new backing file.
-		newMeta.InitProviderBacking(base.DiskFileNum(newMeta.FileNum), inputMeta.FileBacking.Size)
+		newMeta.InitVirtualBacking(base.DiskFileNum(newMeta.FileNum), inputMeta.FileBacking.Size)
 	} else {
 		// local -> shared copy. New file is guaranteed to not be virtual.
 		newMeta.InitPhysicalBacking()

ingest.go

@@ -129,7 +129,7 @@ func ingestSynthesizeShared(
 	// This ensures that we don't over-prioritize this sstable for compaction just
 	// yet, as we do not have a clear sense of what parts of this sstable are
 	// referenced by other nodes.
-	meta.InitProviderBacking(base.DiskFileNum(fileNum), sm.Size)
+	meta.InitVirtualBacking(base.DiskFileNum(fileNum), sm.Size)
 
 	if sm.LargestPointKey.Valid() && sm.LargestPointKey.UserKey != nil {
 		// Initialize meta.{HasPointKeys,Smallest,Largest}, etc.
@@ -768,7 +768,7 @@ func (d *DB) ingestAttachRemote(jobID JobID, lr ingestLoadResult) error {
 		// We have to attach the remote object (and assign it a DiskFileNum). For
 		// simplicity, we use the same number for both the FileNum and the
 		// DiskFileNum (even though this is a virtual sstable).
-		meta.InitProviderBacking(base.DiskFileNum(meta.FileNum), lr.external[i].external.Size)
+		meta.InitVirtualBacking(base.DiskFileNum(meta.FileNum), lr.external[i].external.Size)
 
 		// Set the underlying FileBacking's size to the same size as the virtualized
 		// view of the sstable. This ensures that we don't over-prioritize this

internal/manifest/version.go

@@ -525,24 +525,27 @@ func (m *TableMetadata) InitPhysicalBacking() {
 	if m.Virtual != nil {
 		panic("pebble: virtual sstables should use a pre-existing FileBacking")
 	}
-	if m.FileBacking == nil {
-		m.FileBacking = &FileBacking{
-			DiskFileNum: base.PhysicalTableDiskFileNum(m.FileNum),
-			Size:        m.Size,
-		}
+	if m.FileBacking != nil {
+		panic("backing already initialized")
+	}
+	m.FileBacking = &FileBacking{
+		DiskFileNum: base.PhysicalTableDiskFileNum(m.FileNum),
+		Size:        m.Size,
 	}
 }
 
-// InitProviderBacking creates a new FileBacking for a file backed by
-// an objstorage.Provider.
-func (m *TableMetadata) InitProviderBacking(fileNum base.DiskFileNum, size uint64) {
+// InitVirtualBacking creates a new FileBacking for a virtual table.
+func (m *TableMetadata) InitVirtualBacking(fileNum base.DiskFileNum, size uint64) {
 	if m.Virtual == nil {
 		panic("pebble: provider-backed sstables must be virtual")
 	}
-	if m.FileBacking == nil {
-		m.FileBacking = &FileBacking{DiskFileNum: fileNum}
+	if m.FileBacking != nil {
+		panic("backing already initialized")
+	}
+	m.FileBacking = &FileBacking{
+		DiskFileNum: fileNum,
+		Size:        size,
 	}
-	m.FileBacking.Size = size
 }
 
 // ValidateVirtual should be called once the TableMetadata for a virtual sstable
@@ -927,7 +930,7 @@ func ParseTableMetadataDebug(s string) (_ *TableMetadata, err error) {
 		m.InitPhysicalBacking()
 	} else {
 		m.Virtual = &virtual.VirtualReaderParams{}
-		m.InitProviderBacking(backingNum, 0 /* size */)
+		m.InitVirtualBacking(backingNum, 0 /* size */)
 	}
 	return m, nil
 }