sql: implement hidden column element

This changes moves `ALTER COLUMN SET [NOT] VISIBLE` statements to the
declarative schema changer.

Epic: CRDB-31283
Fixes: #139605

Release note (sql change): The `ALTER TABLE t ALTER COLUMN c SET [NOT]
VISIBLE` statements now use the declarative schema changer.

Author: bghal

pkg/ccl/schemachangerccl/sctestbackupccl/backup_base_generated_test.go

@@ -123,6 +123,12 @@ func executeSupportedDDLs(
 		`ALTER TABLE testdb.testsc.t2 RENAME COLUMN k_renamed TO k`,
 	}
 
+	// DDLs supported in V26_1.
+	v261DDLs := []string{
+		`ALTER TABLE testdb.testsc.t2 ALTER COLUMN j SET NOT VISIBLE`,
+		`ALTER TABLE testdb.testsc.t2 ALTER COLUMN j SET VISIBLE`,
+	}
+
 	// Used to clean up our CREATE-d elements after we are done with them.
 	cleanup := []string{
 		`DROP INDEX testdb.testsc.t@idx`,
@@ -155,6 +161,13 @@ func executeSupportedDDLs(
 			}
 		}
 	}
+	if clusterVersion.AtLeast(clusterversion.V26_1.Version()) {
+		for _, ddl := range v261DDLs {
+			if err := helper.ExecWithGateway(r, nodes, ddl); err != nil {
+				return err
+			}
+		}
+	}
 
 	for _, ddl := range cleanup {
 		if err := helper.ExecWithGateway(r, nodes, ddl); err != nil {

pkg/cmd/roachtest/tests/mixed_version_job_compatibility_in_declarative_schema_changer.go

@@ -14,6 +14,7 @@ go_library(
         "alter_table_alter_column_set_identity.go",
         "alter_table_alter_column_set_not_null.go",
         "alter_table_alter_column_set_on_update.go",
+        "alter_table_alter_column_set_visible.go",
         "alter_table_alter_column_type.go",
         "alter_table_alter_primary_key.go",
         "alter_table_drop_column.go",

pkg/sql/schemachanger/scbuild/internal/scbuildstmt/BUILD.bazel

@@ -26,9 +26,9 @@ import (
 
 type supportedAlterTableCommand = supportedStatement
 
-// supportedAlterTableStatements tracks alter table operations fully supported by
-// declarative schema  changer. Operations marked as non-fully supported can
-// only be with the use_declarative_schema_changer session variable.
+// supportedAlterTableStatements tracks alter table operations fully supported
+// by the declarative schema changer. Operations marked as non-fully supported
+// can only be with the use_declarative_schema_changer session variable.
 var supportedAlterTableStatements = map[reflect.Type]supportedAlterTableCommand{
 	reflect.TypeOf((*tree.AlterTableAddColumn)(nil)):          {fn: alterTableAddColumn, on: true, checks: nil},
 	reflect.TypeOf((*tree.AlterTableDropColumn)(nil)):         {fn: alterTableDropColumn, on: true, checks: nil},
@@ -47,6 +47,7 @@ var supportedAlterTableStatements = map[reflect.Type]supportedAlterTableCommand{
 	reflect.TypeOf((*tree.AlterTableRenameConstraint)(nil)):   {fn: alterTableRenameConstraint, on: true, checks: isV261Active},
 	reflect.TypeOf((*tree.AlterTableSetIdentity)(nil)):        {fn: alterTableSetIdentity, on: true, checks: isV261Active},
 	reflect.TypeOf((*tree.AlterTableAddIdentity)(nil)):        {fn: alterTableAddIdentity, on: true, checks: isV261Active},
+	reflect.TypeOf((*tree.AlterTableSetVisible)(nil)):         {fn: alterTableAlterColumnSetVisible, on: true, checks: isV261Active},
 }
 
 func init() {

pkg/sql/schemachanger/scbuild/internal/scbuildstmt/alter_table.go

@@ -0,0 +1,34 @@
+// Copyright 2025 The Cockroach Authors.
+//
+// Use of this software is governed by the CockroachDB Software License
+// included in the /LICENSE file.
+
+package scbuildstmt
+
+import (
+	"github.com/cockroachdb/cockroach/pkg/sql/schemachanger/scpb"
+	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
+)
+
+func alterTableAlterColumnSetVisible(
+	b BuildCtx,
+	tn *tree.TableName,
+	tbl *scpb.Table,
+	stmt tree.Statement,
+	t *tree.AlterTableSetVisible,
+) {
+	alterColumnPreChecks(b, tn, tbl, t.Column)
+	columnID := getColumnIDFromColumnName(b, tbl.TableID, t.Column, true /* required */)
+	// Block alters on system columns.
+	panicIfSystemColumn(mustRetrieveColumnElem(b, tbl.TableID, columnID), t.Column)
+
+	columnHidden := b.QueryByID(tbl.TableID).FilterColumnHidden().Filter(func(current scpb.Status, target scpb.TargetStatus, e *scpb.ColumnHidden) bool {
+		return e.ColumnID == columnID
+	}).MustGetZeroOrOneElement()
+
+	if columnHidden != nil && t.Visible {
+		b.Drop(columnHidden)
+	} else if columnHidden == nil && !t.Visible {
+		b.Add(&scpb.ColumnHidden{TableID: tbl.TableID, ColumnID: columnID})
+	}
+}

pkg/sql/schemachanger/scbuild/internal/scbuildstmt/alter_table_alter_column_set_visible.go

@@ -0,0 +1,37 @@
+setup
+CREATE TABLE defaultdb.foo (i INT PRIMARY KEY, a INT, b INT NOT VISIBLE);
+----
+
+build
+ALTER TABLE foo ALTER COLUMN a SET VISIBLE
+----
+
+build
+ALTER TABLE foo ALTER COLUMN b SET VISIBLE
+----
+- [[ColumnHidden:{DescID: 104, ColumnID: 3}, ABSENT], PUBLIC]
+  {columnId: 3, tableId: 104}
+- [[IndexData:{DescID: 104, IndexID: 1}, PUBLIC], PUBLIC]
+  {indexId: 1, tableId: 104}
+- [[TableData:{DescID: 104, ReferencedDescID: 100}, PUBLIC], PUBLIC]
+  {databaseId: 100, tableId: 104}
+
+build
+ALTER TABLE foo ALTER COLUMN a SET NOT VISIBLE
+----
+- [[IndexData:{DescID: 104, IndexID: 1}, PUBLIC], PUBLIC]
+  {indexId: 1, tableId: 104}
+- [[TableData:{DescID: 104, ReferencedDescID: 100}, PUBLIC], PUBLIC]
+  {databaseId: 100, tableId: 104}
+- [[ColumnHidden:{DescID: 104, ColumnID: 2}, PUBLIC], ABSENT]
+  {columnId: 2, tableId: 104}
+
+build
+ALTER TABLE foo ALTER COLUMN a SET NOT VISIBLE
+----
+- [[IndexData:{DescID: 104, IndexID: 1}, PUBLIC], PUBLIC]
+  {indexId: 1, tableId: 104}
+- [[TableData:{DescID: 104, ReferencedDescID: 100}, PUBLIC], PUBLIC]
+  {databaseId: 100, tableId: 104}
+- [[ColumnHidden:{DescID: 104, ColumnID: 2}, PUBLIC], ABSENT]
+  {columnId: 2, tableId: 104}

pkg/sql/schemachanger/scbuild/testdata/alter_table_alter_column_visible

@@ -662,7 +662,6 @@ func (w *walkCtx) walkColumn(tbl catalog.TableDescriptor, col catalog.Column) {
 			ColumnID:   col.GetID(),
 		})
 	})
-
 }
 
 func (w *walkCtx) walkIndex(tbl catalog.TableDescriptor, idx catalog.Index) {

pkg/sql/schemachanger/scdecomp/decomp.go

@@ -136,9 +136,7 @@ func VersionSupportsElementUse(el scpb.Element, version clusterversion.ClusterVe
 		return version.IsActive(clusterversion.V25_2)
 	case *scpb.TableLocalityRegionalByRowUsingConstraint:
 		return version.IsActive(clusterversion.V25_3)
-	case *scpb.ColumnGeneratedAsIdentity:
-		return version.IsActive(clusterversion.V26_1)
-	case *scpb.ColumnHidden:
+	case *scpb.ColumnGeneratedAsIdentity, *scpb.ColumnHidden:
 		return version.IsActive(clusterversion.V26_1)
 	default:
 		panic(errors.AssertionFailedf("unknown element %T", el))