sql: turn some catalog.TableDescriptor methods into functions

The catalog.TableDescriptor has ForEach*Index and Find*Index methods
which can just as well be expressed as functions, thereby lightening
that interface definition somewhat.

This patch also adds iterutils.StopIteration() support for the above
ForEach*Index functions, and otherwise also adds comments to many
catalog.Index methods.

Release note: None

pkg/ccl/backupccl/backup_planning.go

@@ -182,7 +182,7 @@ func getLogicallyMergedTableSpans(
 	checkForKVInBounds func(start, end roachpb.Key, endTime hlc.Timestamp) (bool, error),
 ) ([]roachpb.Span, error) {
 	var nonDropIndexIDs []descpb.IndexID
-	if err := table.ForEachNonDropIndex(func(idx catalog.Index) error {
+	if err := catalog.ForEachNonDropIndex(table, func(idx catalog.Index) error {
 		key := tableAndIndex{tableID: table.GetID(), indexID: idx.GetID()}
 		if added[key] {
 			return nil

pkg/ccl/backupccl/restore_planning.go

@@ -1021,7 +1021,7 @@ func RewriteTableDescs(
 			return err
 		}
 
-		if err := table.ForEachNonDropIndex(func(indexI catalog.Index) error {
+		if err := catalog.ForEachNonDropIndex(table, func(indexI catalog.Index) error {
 			index := indexI.IndexDesc()
 			// Verify that for any interleaved index being restored, the interleave
 			// parent is also being restored. Otherwise, the interleave entries in the

pkg/ccl/backupccl/targets.go

@@ -668,7 +668,7 @@ func ensureInterleavesIncluded(tables []catalog.TableDescriptor) error {
 	}
 
 	for _, table := range tables {
-		if err := table.ForEachIndex(catalog.IndexOpts{
+		if err := catalog.ForEachIndex(table, catalog.IndexOpts{
 			AddMutations: true,
 		}, func(index catalog.Index) error {
 			for i := 0; i < index.NumInterleaveAncestors(); i++ {

pkg/ccl/importccl/import_processor.go

@@ -191,7 +191,7 @@ func makeInputConverter(
 	}
 
 	if singleTable != nil {
-		if idx := singleTable.FindDeletableNonPrimaryIndex(func(idx catalog.Index) bool {
+		if idx := catalog.FindDeletableNonPrimaryIndex(singleTable, func(idx catalog.Index) bool {
 			return idx.IsPartial()
 		}); idx != nil {
 			return nil, unimplemented.NewWithIssue(50225, "cannot import into table with partial indexes")

pkg/ccl/partitionccl/partition.go

@@ -275,7 +275,7 @@ func selectPartitionExprs(
 
 	a := &rowenc.DatumAlloc{}
 	var prefixDatums []tree.Datum
-	if err := tableDesc.ForEachIndex(catalog.IndexOpts{
+	if err := catalog.ForEachIndex(tableDesc, catalog.IndexOpts{
 		AddMutations: true,
 	}, func(idx catalog.Index) error {
 		return selectPartitionExprsByName(

pkg/sql/alter_table.go

@@ -816,7 +816,7 @@ func (n *alterTableNode) startExec(params runParams) error {
 			// new name exists. This is what postgres does.
 			switch details.Kind {
 			case descpb.ConstraintTypeUnique, descpb.ConstraintTypePK:
-				if n.tableDesc.FindNonDropIndex(func(idx catalog.Index) bool {
+				if catalog.FindNonDropIndex(n.tableDesc, func(idx catalog.Index) bool {
 					return idx.GetName() == string(t.NewName)
 				}) != nil {
 					return pgerror.Newf(pgcode.DuplicateRelation,

pkg/sql/catalog/BUILD.bazel

@@ -26,6 +26,7 @@ go_library(
         "//pkg/sql/types",
         "//pkg/util",
         "//pkg/util/hlc",
+        "//pkg/util/iterutil",
         "@com_github_cockroachdb_errors//:errors",
         "@com_github_cockroachdb_redact//:redact",
     ],