schemadiff: explicit ALGORITHM=INSTANT counts as instant-able (#1…

…7942)

Signed-off-by: Shlomi Noach <[email protected]>

go/vt/schemadiff/capability.go

@@ -223,6 +223,9 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
 			return capableOf(capabilities.InstantChangeColumnVisibilityCapability)
 		}
 		return false, nil
+	case sqlparser.AlgorithmValue:
+		// We accept an explicit ALGORITHM=INSTANT option.
+		return strings.EqualFold(string(opt), sqlparser.InstantStr), nil
 	default:
 		return false, nil
 	}

go/vt/schemadiff/capability_test.go

@@ -345,6 +345,24 @@ func TestAlterTableCapableOfInstantDDL(t *testing.T) {
 			alter:                     "alter table t1 alter column i1 drop default",
 			expectCapableOfInstantDDL: true,
 		},
+		{
+			name:                      "add column with explicit ALGORITHM=instant",
+			create:                    "create table t1 (id int, i1 int)",
+			alter:                     "alter table t1 add column i2 int, algorithm=instant",
+			expectCapableOfInstantDDL: true,
+		},
+		{
+			name:                      "add column with explicit ALGORITHM=INSTANT",
+			create:                    "create table t1 (id int, i1 int)",
+			alter:                     "alter table t1 add column i2 int, algorithm=INSTANT",
+			expectCapableOfInstantDDL: true,
+		},
+		{
+			name:                      "reject if ALGORITHM=COPY",
+			create:                    "create table t1 (id int, i1 int)",
+			alter:                     "alter table t1 add column i2 int, algorithm=COPY",
+			expectCapableOfInstantDDL: false,
+		},
 	}
 	for _, tcase := range tcases {
 		t.Run(tcase.name, func(t *testing.T) {