db: avoid use of internal type in ValueSeparationPolicy

Avoid use of the internal/manifest.BlobReferenceDepth type in the external
ValueSeparationPolicy type. Users are expected to construct a
ValueSeparationPolicy and must be able to construct a MaxBlobReferenceDepth
value.

Author: jbowens

data_test.go

@@ -1675,12 +1675,10 @@ func parseDBOptionsArgs(opts *Options, args []datadriven.CmdArg) error {
 			if err != nil {
 				return err
 			}
-			var maxDepth int
-			maxDepth, err = strconv.Atoi(cmdArg.Vals[2])
+			policy.MaxBlobReferenceDepth, err = strconv.Atoi(cmdArg.Vals[2])
 			if err != nil {
 				return err
 			}
-			policy.MaxBlobReferenceDepth = manifest.BlobReferenceDepth(maxDepth)
 			opts.Experimental.ValueSeparationPolicy = func() ValueSeparationPolicy {
 				return policy
 			}

options.go

@@ -1140,7 +1140,7 @@ type ValueSeparationPolicy struct {
 	// compaction may produce an output sstable referencing more than this many
 	// overlapping blob files, the compaction will instead rewrite referenced
 	// values into new blob files.
-	MaxBlobReferenceDepth manifest.BlobReferenceDepth
+	MaxBlobReferenceDepth int
 }
 
 // WALFailoverOptions configures the WAL failover mechanics to use during
@@ -1928,9 +1928,7 @@ func (o *Options) Parse(s string, hooks *ParseHooks) error {
 				minimumSize, err = strconv.Atoi(value)
 				valSepPolicy.MinimumSize = minimumSize
 			case "max_blob_reference_depth":
-				var maxBlobReferenceDepth int
-				maxBlobReferenceDepth, err = strconv.Atoi(value)
-				valSepPolicy.MaxBlobReferenceDepth = manifest.BlobReferenceDepth(maxBlobReferenceDepth)
+				valSepPolicy.MaxBlobReferenceDepth, err = strconv.Atoi(value)
 			default:
 				if hooks != nil && hooks.SkipUnknown != nil && hooks.SkipUnknown(section+"."+key, value) {
 					return nil

value_separation.go

@@ -65,29 +65,29 @@ func (d *DB) determineCompactionValueSeparation(
 }
 
 // shouldWriteBlobFiles returns true if the compaction should write new blob
-// files. It also returns the maximum blob reference depth to assign to output
-// sstables (the actual value may be lower iff the output table references fewer
-// distinct blob files).
+// files. If it returns false, the referenceDepth return value contains the
+// maximum blob reference depth to assign to output sstables (the actual value
+// may be lower iff the output table references fewer distinct blob files).
 func shouldWriteBlobFiles(
 	c *compaction, policy ValueSeparationPolicy,
 ) (writeBlobs bool, referenceDepth manifest.BlobReferenceDepth) {
 	// Flushes will have no existing references to blob files and should write
 	// their values to new blob files.
 	if c.kind == compactionKindFlush {
-		return true, 1
+		return true, 0
 	}
 	inputReferenceDepth := compactionBlobReferenceDepth(c.inputs)
 	if inputReferenceDepth == 0 {
 		// None of the input sstables reference blob files. It may be the case
 		// that these sstables were created before value separation was enabled.
 		// We should try to write to new blob files.
-		return true, 1
+		return true, 0
 	}
 	// If the compaction's output blob reference depth would be greater than the
 	// configured max, we should rewrite the values into new blob files to
 	// restore locality.
-	if inputReferenceDepth > policy.MaxBlobReferenceDepth {
-		return true, 1
+	if inputReferenceDepth > manifest.BlobReferenceDepth(policy.MaxBlobReferenceDepth) {
+		return true, 0
 	}
 	// Otherwise, we won't write any new blob files but will carry forward
 	// existing references.