schemadiff: DROP COLUMN not eligible for INSTANT if covered by an index

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

go/vt/schemadiff/capability.go

@@ -21,6 +21,16 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
  }
  return nil
  }
+ findIndexCoveringColumn := func(colName string) *sqlparser.IndexDefinition {
+ for _, index := range createTable.TableSpec.Indexes {
+ for _, col := range index.Columns {
+ if col.Column.String() == colName {
+ return index
+ }
+ }
+ }
+ return nil
+ }
  findTableOption := func(optName string) *sqlparser.TableOption {
  if createTable == nil {
  return nil
@@ -90,6 +100,10 @@ func alterOptionCapableOfInstantDDL(alterOption sqlparser.AlterOption, createTab
  return false, nil
  }
  }
+ if findIndexCoveringColumn(opt.Name.Name.String()) != nil {
+ // not supported if the column is part of an index
+ return false, nil
+ }
  if isVirtualColumn(opt.Name.Name.String()) {
  // supported by all 8.0 versions
  return capableOf(capabilities.InstantAddDropVirtualColumnFlavorCapability)

go/vt/schemadiff/capability_test.go

@@ -85,6 +85,12 @@ func TestAlterTableCapableOfInstantDDL(t *testing.T) {
  alter: "alter table t drop column i1",
  expectCapableOfInstantDDL: false,
  },
+ {
+ name: "drop column fail due to index",
+ create: "create table t(id int, i1 int not null, i2 int not null, primary key(id), key i1_idx (i1))",
+ alter: "alter table t drop column i1",
+ expectCapableOfInstantDDL: false,
+ },
  {
  name: "add two columns",
  create: "create table t(id int, i1 int not null, primary key(id))",