sql: stop setting readAsOf in index backfiller

As of the parent commit, this is unused by the index backfiller.

Release note: None

Author: rafiss

pkg/sql/backfill.go

@@ -1012,8 +1012,6 @@ func (sc *SchemaChanger) distIndexBackfill(
 		log.Infof(ctx, "writing at persisted safe write time %v...", writeAsOf)
 	}
 
-	readAsOf := sc.clock.Now()
-
 	var p *PhysicalPlan
 	var extEvalCtx extendedEvalContext
 	var planCtx *PlanningCtx
@@ -1045,7 +1043,7 @@ func (sc *SchemaChanger) distIndexBackfill(
 		)
 		indexBatchSize := indexBackfillBatchSize.Get(&sc.execCfg.Settings.SV)
 		chunkSize := sc.getChunkSize(indexBatchSize)
-		spec, err := initIndexBackfillerSpec(*tableDesc.TableDesc(), writeAsOf, readAsOf, writeAtRequestTimestamp, chunkSize, addedIndexes, 0 /* sourceIndexID*/)
+		spec, err := initIndexBackfillerSpec(*tableDesc.TableDesc(), writeAsOf, writeAtRequestTimestamp, chunkSize, addedIndexes, 0)
 		if err != nil {
 			return err
 		}

pkg/sql/distsql_plan_backfill.go

@@ -40,7 +40,7 @@ func initColumnBackfillerSpec(
 
 func initIndexBackfillerSpec(
 	desc descpb.TableDescriptor,
-	writeAsOf, readAsOf hlc.Timestamp,
+	writeAsOf hlc.Timestamp,
 	writeAtBatchTimestamp bool,
 	chunkSize int64,
 	indexesToBackfill []descpb.IndexID,
@@ -50,7 +50,6 @@ func initIndexBackfillerSpec(
 		Table:                 desc,
 		WriteAsOf:             writeAsOf,
 		WriteAtBatchTimestamp: writeAtBatchTimestamp,
-		ReadAsOf:              readAsOf,
 		Type:                  execinfrapb.BackfillerSpec_Index,
 		ChunkSize:             chunkSize,
 		IndexesToBackfill:     indexesToBackfill,

pkg/sql/execinfrapb/processors_bulk_io.proto

@@ -61,9 +61,9 @@ message BackfillerSpec {
   optional uint64 update_chunk_size_threshold_bytes = 14 [(gogoproto.nullable) = false];
 
   // WriteAsOf is the time that the backfill entries should be written.
-  // Note: Older nodes may also use this as the read time instead of readAsOf.
   optional util.hlc.Timestamp writeAsOf = 7 [(gogoproto.nullable) = false];
   // The timestamp to perform index backfill historical scans at.
+  // This is only used by the column backfiller.
   optional util.hlc.Timestamp readAsOf = 9 [(gogoproto.nullable) = false];
 
   // IndexesToBackfill is the set of indexes to backfill. This is populated only

pkg/sql/index_backfiller.go

@@ -184,9 +184,8 @@ func (ib *IndexBackfillPlanner) plan(
 		chunkSize := indexBackfillBatchSize.Get(&ib.execCfg.Settings.SV)
 		const writeAtRequestTimestamp = true
 		spec, err := initIndexBackfillerSpec(
-			*td.TableDesc(), writeAsOf, readAsOf, writeAtRequestTimestamp, chunkSize,
-			indexesToBackfill,
-			sourceIndexID,
+			*td.TableDesc(), writeAsOf, writeAtRequestTimestamp, chunkSize,
+			indexesToBackfill, sourceIndexID,
 		)
 		if err != nil {
 			return err