func getTableDescriptor(db *client.DB, database string, table string) *sqlbase.TableDescriptor {
	dbNameKey := sqlbase.MakeNameMetadataKey(keys.RootNamespaceID, database)
	gr, err := db.Get(dbNameKey)
	if err != nil {
		panic(err)
	}
	if !gr.Exists() {
		panic("database missing")
	}
	dbDescID := sqlbase.ID(gr.ValueInt())

	tableNameKey := sqlbase.MakeNameMetadataKey(dbDescID, table)
	gr, err = db.Get(tableNameKey)
	if err != nil {
		panic(err)
	}
	if !gr.Exists() {
		panic("table missing")
	}

	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := db.GetProto(descKey, desc); err != nil {
		panic("proto missing")
	}
	return desc.GetTable()
}

// getTableNames implements the SchemaAccessor interface.
func (p *planner) getTableNames(dbDesc *sqlbase.DatabaseDescriptor) (parser.QualifiedNames, error) {
	prefix := sqlbase.MakeNameMetadataKey(dbDesc.ID, "")
	sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if err != nil {
		return nil, err
	}

	var qualifiedNames parser.QualifiedNames
	for _, row := range sr {
		_, tableName, err := encoding.DecodeUnsafeStringAscending(
			bytes.TrimPrefix(row.Key, prefix), nil)
		if err != nil {
			return nil, err
		}
		qname := &parser.QualifiedName{
			Base:     parser.Name(dbDesc.Name),
			Indirect: parser.Indirection{parser.NameIndirection(tableName)},
		}
		if err := qname.NormalizeTableName(""); err != nil {
			return nil, err
		}
		qualifiedNames = append(qualifiedNames, qname)
	}
	return qualifiedNames, nil
}

// getTableNames implements the SchemaAccessor interface.
func (p *planner) getTableNames(dbDesc *sqlbase.DatabaseDescriptor) (parser.TableNames, error) {
	if e, ok := getVirtualSchemaEntry(dbDesc.Name); ok {
		return e.tableNames(), nil
	}

	prefix := sqlbase.MakeNameMetadataKey(dbDesc.ID, "")
	sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if err != nil {
		return nil, err
	}

	var tableNames parser.TableNames
	for _, row := range sr {
		_, tableName, err := encoding.DecodeUnsafeStringAscending(
			bytes.TrimPrefix(row.Key, prefix), nil)
		if err != nil {
			return nil, err
		}
		tn := parser.TableName{
			DatabaseName: parser.Name(dbDesc.Name),
			TableName:    parser.Name(tableName),
		}
		tableNames = append(tableNames, tn)
	}
	return tableNames, nil
}

// getKeysForTableDescriptor retrieves the KV keys corresponding
// to the zone, name and descriptor of a table.
func getKeysForTableDescriptor(
	tableDesc *sqlbase.TableDescriptor,
) (zoneKey roachpb.Key, nameKey roachpb.Key, descKey roachpb.Key) {
	zoneKey = sqlbase.MakeZoneKey(tableDesc.ID)
	nameKey = sqlbase.MakeNameMetadataKey(tableDesc.ParentID, tableDesc.GetName())
	descKey = sqlbase.MakeDescMetadataKey(tableDesc.ID)
	return
}

func getKeysForDatabaseDescriptor(
	dbDesc *sqlbase.DatabaseDescriptor,
) (zoneKey roachpb.Key, nameKey roachpb.Key, descKey roachpb.Key) {
	zoneKey = sqlbase.MakeZoneKey(dbDesc.ID)
	nameKey = sqlbase.MakeNameMetadataKey(keys.RootNamespaceID, dbDesc.GetName())
	descKey = sqlbase.MakeDescMetadataKey(dbDesc.ID)
	return
}

// ShowDatabases returns all the databases.
// Privileges: None.
//   Notes: postgres does not have a "show databases"
//          mysql has a "SHOW DATABASES" permission, but we have no system-level permissions.
func (p *planner) ShowDatabases(n *parser.ShowDatabases) (planNode, error) {
	// TODO(pmattis): This could be implemented as:
	//
	//   SELECT id FROM system.namespace WHERE parentID = 0

	prefix := sqlbase.MakeNameMetadataKey(keys.RootNamespaceID, "")
	sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if err != nil {
		return nil, err
	}
	v := &valuesNode{columns: []ResultColumn{{Name: "Database", Typ: parser.TypeString}}}
	for _, row := range sr {
		_, name, err := encoding.DecodeUnsafeStringAscending(
			bytes.TrimPrefix(row.Key, prefix), nil)
		if err != nil {
			return nil, err
		}
		v.rows = append(v.rows, []parser.Datum{parser.NewDString(name)})
	}
	return v, nil
}

func TestDropTable(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, sqlDB, kvDB := setup(t)
	defer cleanup(s, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.kv (k CHAR PRIMARY KEY, v CHAR);
INSERT INTO t.kv VALUES ('c', 'e'), ('a', 'c'), ('b', 'd');
`); err != nil {
		t.Fatal(err)
	}

	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "kv")
	gr, pErr := kvDB.Get(nameKey)
	if pErr != nil {
		t.Fatal(pErr)
	}

	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}

	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if pErr := kvDB.GetProto(descKey, desc); pErr != nil {
		t.Fatal(pErr)
	}
	tableDesc := desc.GetTable()

	// Add a zone config for the table.
	cfg := config.DefaultZoneConfig()
	buf, err := protoutil.Marshal(&cfg)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := sqlDB.Exec(`INSERT INTO system.zones VALUES ($1, $2)`, tableDesc.ID, buf); err != nil {
		t.Fatal(err)
	}

	zoneKey := sqlbase.MakeZoneKey(tableDesc.ID)
	if gr, err := kvDB.Get(zoneKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatalf("zone config entry not found")
	}

	tablePrefix := keys.MakeTablePrefix(uint32(tableDesc.ID))
	tableStartKey := roachpb.Key(tablePrefix)
	tableEndKey := tableStartKey.PrefixEnd()
	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 6; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if _, err := sqlDB.Exec(`DROP TABLE t.kv`); err != nil {
		t.Fatal(err)
	}

	// Test that deleted table cannot be used. This prevents regressions where
	// name -> descriptor ID caches might make this statement erronously work.
	if _, err := sqlDB.Exec(`SELECT * FROM t.kv`); !testutils.IsError(err, `table "t.kv" does not exist`) {
		t.Fatalf("different error than expected: %s", err)
	}

	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 0; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if gr, err := kvDB.Get(descKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("table descriptor still exists after the table is dropped")
	}

	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("table namekey still exists after the table is dropped")
	}

	if gr, err := kvDB.Get(zoneKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("zone config entry still exists after the table is dropped")
	}
}

func TestDropIndex(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, sqlDB, kvDB := setup(t)
	defer cleanup(s, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.kv (k CHAR PRIMARY KEY, v CHAR);
CREATE INDEX foo on t.kv (v);
INSERT INTO t.kv VALUES ('c', 'e'), ('a', 'c'), ('b', 'd');
`); err != nil {
		t.Fatal(err)
	}

	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "kv")
	gr, pErr := kvDB.Get(nameKey)
	if pErr != nil {
		t.Fatal(pErr)
	}

	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}

	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if pErr := kvDB.GetProto(descKey, desc); pErr != nil {
		t.Fatal(pErr)
	}
	tableDesc := desc.GetTable()

	status, i, err := tableDesc.FindIndexByName("foo")
	if err != nil {
		t.Fatal(err)
	}
	if status != sqlbase.DescriptorActive {
		t.Fatal("Index 'foo' is not active.")
	}
	indexPrefix := sqlbase.MakeIndexKeyPrefix(tableDesc.ID, tableDesc.Indexes[i].ID)

	indexStartKey := roachpb.Key(indexPrefix)
	indexEndKey := indexStartKey.PrefixEnd()
	if kvs, err := kvDB.Scan(indexStartKey, indexEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 3; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if _, err := sqlDB.Exec(`DROP INDEX [email protected]`); err != nil {
		t.Fatal(err)
	}

	if kvs, err := kvDB.Scan(indexStartKey, indexEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 0; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	tableDesc = desc.GetTable()
	if _, _, err := tableDesc.FindIndexByName("foo"); err == nil {
		t.Fatalf("table descriptor still contains index after index is dropped")
	}
	if err != nil {
		t.Fatal(err)
	}
}

func TestCommandsWithPendingMutations(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	// Disable external processing of mutations.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs.SQLSchemaChangeManager = &csql.SchemaChangeManagerTestingKnobs{
		AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (a CHAR PRIMARY KEY, b CHAR, c CHAR, INDEX foo (c));
`); err != nil {
		t.Fatal(err)
	}

	// Read table descriptor
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}

	mt := mutationTest{
		T:       t,
		kvDB:    kvDB,
		sqlDB:   sqlDB,
		descKey: descKey,
		desc:    desc,
	}

	// Test CREATE INDEX in the presence of mutations.

	// Add index DROP mutation "foo""
	mt.writeIndexMutation("foo", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_DROP})
	if _, err := sqlDB.Exec(`CREATE INDEX foo ON t.test (c)`); !testutils.IsError(err, `index "foo" being dropped, try again later`) {
		t.Fatal(err)
	}
	// Make "foo" live.
	mt.makeMutationsActive()

	// "foo" is being added.
	mt.writeIndexMutation("foo", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_ADD})
	if _, err := sqlDB.Exec(`CREATE INDEX foo ON t.test (c)`); !testutils.IsError(err, `duplicate index name: "foo"`) {
		t.Fatal(err)
	}
	// Make "foo" live.
	mt.makeMutationsActive()
	// Add column DROP mutation "b"
	mt.writeColumnMutation("b", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_DROP})
	if _, err := sqlDB.Exec(`CREATE INDEX bar ON t.test (b)`); !testutils.IsError(err, `index "bar" contains unknown column "b"`) {
		t.Fatal(err)
	}
	// Make "b" live.
	mt.makeMutationsActive()
	// "b" is being added.
	mt.writeColumnMutation("b", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_ADD})
	// An index referencing a column mutation that is being added
	// is allowed to be added.
	if _, err := sqlDB.Exec(`CREATE INDEX bar ON t.test (b)`); err != nil {
		t.Fatal(err)
	}
	// Make "b" live.
	mt.makeMutationsActive()

	// Test DROP INDEX in the presence of mutations.

	// Add index DROP mutation "foo""
	mt.writeIndexMutation("foo", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_DROP})
	// Noop.
	if _, err := sqlDB.Exec(`DROP INDEX [email protected]`); err != nil {
		t.Fatal(err)
	}
	// Make "foo" live.
	mt.makeMutationsActive()
	// "foo" is being added.
	mt.writeIndexMutation("foo", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_ADD})
	if _, err := sqlDB.Exec(`DROP INDEX [email protected]`); !testutils.IsError(err, `index "foo" in the middle of being added, try again later`) {
		t.Fatal(err)
	}
	// Make "foo" live.
	mt.makeMutationsActive()
	// Test ALTER TABLE ADD/DROP column in the presence of mutations.

	// Add column DROP mutation "b"
	mt.writeColumnMutation("b", sqlbase.DescriptorMutation{Direction: sqlbase.DescriptorMutation_DROP})
	if _, err := sqlDB.Exec(`ALTER TABLE t.test ADD b CHAR`); !testutils.IsError(err, `column "b" being dropped, try again later`) {
		t.Fatal(err)
//.........这里部分代码省略.........

// TestOperationsWithUniqueColumnMutation tests all the operations while an
// index mutation refers to a column mutation.
func TestOperationsWithUniqueColumnMutation(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	// Disable external processing of mutations.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs.SQLSchemaChangeManager = &csql.SchemaChangeManagerTestingKnobs{
		AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	// Create a table with column i and an index on v and i.
	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k CHAR PRIMARY KEY, v CHAR, i CHAR, INDEX foo (i, v));
`); err != nil {
		t.Fatal(err)
	}

	// read table descriptor
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}

	mTest := mutationTest{
		T:       t,
		kvDB:    kvDB,
		sqlDB:   sqlDB,
		descKey: descKey,
		desc:    desc,
	}

	starQuery := `SELECT * FROM t.test`
	indexQuery := `SELECT i FROM [email protected]`
	// Run the tests for both states.
	for _, state := range []sqlbase.DescriptorMutation_State{
		sqlbase.DescriptorMutation_DELETE_ONLY,
		sqlbase.DescriptorMutation_WRITE_ONLY,
	} {
		// Init table to start state.
		if _, err := sqlDB.Exec(`TRUNCATE TABLE t.test`); err != nil {
			t.Fatal(err)
		}
		initRows := [][]string{{"a", "z", "q"}}
		for _, row := range initRows {
			if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ($1, $2, $3)`, row[0], row[1], row[2]); err != nil {
				t.Fatal(err)
			}
		}
		// Check that the table only contains the initRows.
		_ = mTest.checkQueryResponse(starQuery, initRows)

		// Add index "foo" as a mutation.
		mTest.writeIndexMutation("foo", sqlbase.DescriptorMutation{State: state})
		// Make column "i" a mutation.
		mTest.writeColumnMutation("i", sqlbase.DescriptorMutation{State: state})

		// Insert a row into the table.
		if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ('c', 'x')`); err != nil {
			t.Error(err)
		}

		// Make column "i" and index "foo" live.
		mTest.makeMutationsActive()
		// column "i" has no entry.
		_ = mTest.checkQueryResponse(starQuery, [][]string{{"a", "z", "q"}, {"c", "x", "NULL"}})
		if state == sqlbase.DescriptorMutation_DELETE_ONLY {
			// No index entry for row "c"
			_ = mTest.checkQueryResponse(indexQuery, [][]string{{"q"}})
		} else {
			// Index entry for row "c"
			_ = mTest.checkQueryResponse(indexQuery, [][]string{{"NULL"}, {"q"}})
		}

		// Add index "foo" as a mutation.
		mTest.writeIndexMutation("foo", sqlbase.DescriptorMutation{State: state})
		// Make column "i" a mutation.
		mTest.writeColumnMutation("i", sqlbase.DescriptorMutation{State: state})

		// Updating column "i" for a row fails.
		if _, err := sqlDB.Exec(`UPDATE t.test SET (v, i) = ('u', 'u') WHERE k = 'a'`); !testutils.IsError(err, `column "i" does not exist`) {
			t.Error(err)
		}

		// TODO(vivek): Fix #6691.
		// Update a row without specifying  mutation column "i".
//.........这里部分代码省略.........

func TestOperationsWithIndexMutation(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect.
	defer csql.TestDisableTableLeases()()
	// Disable external processing of mutations.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs.SQLSchemaChangeManager = &csql.SchemaChangeManagerTestingKnobs{
		AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k CHAR PRIMARY KEY, v CHAR, INDEX foo (v));
`); err != nil {
		t.Fatal(err)
	}

	// read table descriptor
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}

	mTest := mutationTest{
		T:       t,
		kvDB:    kvDB,
		sqlDB:   sqlDB,
		descKey: descKey,
		desc:    desc,
	}

	starQuery := `SELECT * FROM t.test`
	indexQuery := `SELECT v FROM [email protected]`
	// See the effect of the operations depending on the state.
	for _, state := range []sqlbase.DescriptorMutation_State{sqlbase.DescriptorMutation_DELETE_ONLY, sqlbase.DescriptorMutation_WRITE_ONLY} {
		// Init table with some entries.
		if _, err := sqlDB.Exec(`TRUNCATE TABLE t.test`); err != nil {
			t.Fatal(err)
		}
		initRows := [][]string{{"a", "z"}, {"b", "y"}}
		for _, row := range initRows {
			if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ($1, $2)`, row[0], row[1]); err != nil {
				t.Fatal(err)
			}
		}
		_ = mTest.checkQueryResponse(starQuery, initRows)
		// Index foo is visible.
		_ = mTest.checkQueryResponse(indexQuery, [][]string{{"y"}, {"z"}})

		// Index foo is invisible once it's a mutation.
		mTest.writeIndexMutation("foo", sqlbase.DescriptorMutation{State: state})
		if _, err := sqlDB.Query(indexQuery); !testutils.IsError(err, `index "foo" not found`) {
			t.Fatal(err)
		}

		// Insert a new entry.
		if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ('c', 'x')`); err != nil {
			t.Fatal(err)
		}
		_ = mTest.checkQueryResponse(starQuery, [][]string{{"a", "z"}, {"b", "y"}, {"c", "x"}})

		// Make index "foo" live so that we can read it.
		mTest.makeMutationsActive()
		if state == sqlbase.DescriptorMutation_DELETE_ONLY {
			// "x" didn't get added to the index.
			_ = mTest.checkQueryResponse(indexQuery, [][]string{{"y"}, {"z"}})
		} else {
			// "x" got added to the index.
			_ = mTest.checkQueryResponse(indexQuery, [][]string{{"x"}, {"y"}, {"z"}})
		}

		// Make "foo" a mutation.
		mTest.writeIndexMutation("foo", sqlbase.DescriptorMutation{State: state})
		// Update.
		if _, err := sqlDB.Exec(`UPDATE t.test SET v = 'w' WHERE k = 'c'`); err != nil {
			t.Fatal(err)
		}
		// Update "v" to its current value "z" in row "a".
		if _, err := sqlDB.Exec(`UPDATE t.test SET v = 'z' WHERE k = 'a'`); err != nil {
			t.Fatal(err)
		}
		_ = mTest.checkQueryResponse(starQuery, [][]string{{"a", "z"}, {"b", "y"}, {"c", "w"}})

		// Make index "foo" live so that we can read it.
		mTest.makeMutationsActive()
		if state == sqlbase.DescriptorMutation_DELETE_ONLY {
			// updating "x" -> "w" is a noop on the index,
			// updating "z" -> "z" results in "z" being deleted from the index.
			_ = mTest.checkQueryResponse(indexQuery, [][]string{{"y"}, {"z"}})
//.........这里部分代码省略.........

func TestOperationsWithColumnMutation(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	// Disable external processing of mutations.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs.SQLSchemaChangeManager = &csql.SchemaChangeManagerTestingKnobs{
		AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k CHAR PRIMARY KEY, v CHAR, i CHAR DEFAULT 'i');
`); err != nil {
		t.Fatal(err)
	}

	// read table descriptor
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}

	mTest := mutationTest{
		T:       t,
		kvDB:    kvDB,
		sqlDB:   sqlDB,
		descKey: descKey,
		desc:    desc,
	}

	starQuery := `SELECT * FROM t.test`
	// Run the tests for both states.
	for _, state := range []sqlbase.DescriptorMutation_State{sqlbase.DescriptorMutation_DELETE_ONLY, sqlbase.DescriptorMutation_WRITE_ONLY} {
		// Init table to start state.
		if _, err := sqlDB.Exec(`TRUNCATE TABLE t.test`); err != nil {
			t.Fatal(err)
		}
		initRows := [][]string{{"a", "z", "q"}}
		for _, row := range initRows {
			if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ($1, $2, $3)`, row[0], row[1], row[2]); err != nil {
				t.Fatal(err)
			}
		}
		// Check that the table only contains the initRows.
		_ = mTest.checkQueryResponse(starQuery, initRows)

		// Add column "i" as a mutation.
		mTest.writeColumnMutation("i", sqlbase.DescriptorMutation{State: state})
		// A direct read of column "i" fails.
		if _, err := sqlDB.Query(`SELECT i FROM t.test`); err == nil {
			t.Fatalf("Read succeeded despite column being in %v state", sqlbase.DescriptorMutation{State: state})
		}
		// The table only contains columns "k" and "v".
		_ = mTest.checkQueryResponse(starQuery, [][]string{{"a", "z"}})

		// The column backfill uses Put instead of CPut because it depends on
		// an INSERT of a column in the WRITE_ONLY state failing. These two
		// tests guarantee that.

		// Inserting a row into the table while specifying column "i" results in an error.
		if _, err := sqlDB.Exec(`INSERT INTO t.test (k, v, i) VALUES ('b', 'y', 'i')`); !testutils.IsError(err, `column "i" does not exist`) {
			t.Fatal(err)
		}
		// Repeating the same without specifying the columns results in a different error.
		if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ('b', 'y', 'i')`); !testutils.IsError(err, "INSERT has more expressions than target columns: 3/2") {
			t.Fatal(err)
		}
		// Make column "i" live so that it is read.
		mTest.makeMutationsActive()
		// Check that we can read all the rows and columns.
		_ = mTest.checkQueryResponse(starQuery, initRows)

		var afterInsert, afterUpdate, afterDelete [][]string
		if state == sqlbase.DescriptorMutation_DELETE_ONLY {
			// The default value of "i" for column "i" is not written.
			afterInsert = [][]string{{"a", "z", "q"}, {"c", "x", "NULL"}}
			// Update is a noop for column "i".
			afterUpdate = [][]string{{"a", "u", "q"}, {"c", "x", "NULL"}}
			// Delete also deletes column "i".
			afterDelete = [][]string{{"c", "x", "NULL"}}
		} else {
			// The default value of "i" for column "i" is written.
			afterInsert = [][]string{{"a", "z", "q"}, {"c", "x", "i"}}
			// Update is a noop for column "i".
			afterUpdate = [][]string{{"a", "u", "q"}, {"c", "x", "i"}}
			// Delete also deletes column "i".
			afterDelete = [][]string{{"c", "x", "i"}}
//.........这里部分代码省略.........

func (tk tableKey) Key() roachpb.Key {
	return sqlbase.MakeNameMetadataKey(tk.parentID, tk.name)
}

func TestDropDatabase(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, sqlDB, kvDB := setup(t)
	defer cleanup(s, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.kv (k CHAR PRIMARY KEY, v CHAR);
INSERT INTO t.kv VALUES ('c', 'e'), ('a', 'c'), ('b', 'd');
`); err != nil {
		t.Fatal(err)
	}

	dbNameKey := sqlbase.MakeNameMetadataKey(keys.RootNamespaceID, "t")
	r, pErr := kvDB.Get(dbNameKey)
	if pErr != nil {
		t.Fatal(pErr)
	}
	if !r.Exists() {
		t.Fatalf(`database "t" does not exist`)
	}
	dbDescKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(r.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if pErr := kvDB.GetProto(dbDescKey, desc); pErr != nil {
		t.Fatal(pErr)
	}
	dbDesc := desc.GetDatabase()

	tbNameKey := sqlbase.MakeNameMetadataKey(dbDesc.ID, "kv")
	gr, pErr := kvDB.Get(tbNameKey)
	if pErr != nil {
		t.Fatal(pErr)
	}
	if !gr.Exists() {
		t.Fatalf(`table "kv" does not exist`)
	}
	tbDescKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	if pErr := kvDB.GetProto(tbDescKey, desc); pErr != nil {
		t.Fatal(pErr)
	}
	tbDesc := desc.GetTable()

	// Add a zone config for both the table and database.
	cfg := config.DefaultZoneConfig()
	buf, err := protoutil.Marshal(&cfg)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := sqlDB.Exec(`INSERT INTO system.zones VALUES ($1, $2)`, tbDesc.ID, buf); err != nil {
		t.Fatal(err)
	}
	if _, err := sqlDB.Exec(`INSERT INTO system.zones VALUES ($1, $2)`, dbDesc.ID, buf); err != nil {
		t.Fatal(err)
	}

	tbZoneKey := sqlbase.MakeZoneKey(tbDesc.ID)
	dbZoneKey := sqlbase.MakeZoneKey(dbDesc.ID)
	if gr, err := kvDB.Get(tbZoneKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatalf("table zone config entry not found")
	}
	if gr, err := kvDB.Get(dbZoneKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatalf("database zone config entry not found")
	}

	tablePrefix := keys.MakeTablePrefix(uint32(tbDesc.ID))
	tableStartKey := roachpb.Key(tablePrefix)
	tableEndKey := tableStartKey.PrefixEnd()
	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 6; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if _, err := sqlDB.Exec(`DROP DATABASE t`); err != nil {
		t.Fatal(err)
	}

	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 0; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if gr, err := kvDB.Get(tbDescKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("table descriptor still exists after database is dropped: %q", tbDescKey)
	}

	if gr, err := kvDB.Get(tbNameKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("table descriptor key still exists after database is dropped")
	}

	if gr, err := kvDB.Get(dbDescKey); err != nil {
//.........这里部分代码省略.........

// Test schema change purge failure doesn't leave DB in a bad state.
func TestSchemaChangePurgeFailure(t *testing.T) {
	defer leaktest.AfterTest(t)()

	// Disable the async schema changer.
	var enableAsyncSchemaChanges uint32

	attempts := 0
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs = base.TestingKnobs{
		SQLExecutor: &csql.ExecutorTestingKnobs{
			SchemaChangersStartBackfillNotification: func() error {
				attempts++
				// Return a deadline exceeded error during the second attempt
				// which attempts to clean up the schema change.
				if attempts == 2 {
					return errors.New("context deadline exceeded")
				}
				return nil
			},
		},
		SQLSchemaChangeManager: &csql.SchemaChangeManagerTestingKnobs{
			AsyncSchemaChangerExecNotification: func() error {
				if enable := atomic.LoadUint32(&enableAsyncSchemaChanges); enable == 0 {
					return errors.New("async schema changes are disabled")
				}
				return nil
			},
			// Speed up evaluation of async schema changes so that it
			// processes a purged schema change quickly.
			AsyncSchemaChangerExecQuickly: true,
		},
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k INT PRIMARY KEY, v INT);
`); err != nil {
		t.Fatal(err)
	}

	// Bulk insert.
	maxValue := csql.IndexBackfillChunkSize + 1
	insert := fmt.Sprintf(`INSERT INTO t.test VALUES (%d, %d)`, 0, maxValue)
	for i := 1; i <= maxValue; i++ {
		insert += fmt.Sprintf(` ,(%d, %d)`, i, maxValue-i)
	}
	if _, err := sqlDB.Exec(insert); err != nil {
		t.Fatal(err)
	}

	// Add a row with a duplicate value for v
	if _, err := sqlDB.Exec(
		`INSERT INTO t.test VALUES ($1, $2)`, maxValue+1, maxValue,
	); err != nil {
		t.Fatal(err)
	}

	// A schema change that violates integrity constraints.
	if _, err := sqlDB.Exec(
		"CREATE UNIQUE INDEX foo ON t.test (v)",
	); !testutils.IsError(err, "violates unique constraint") {
		t.Fatal(err)
	}
	// The deadline exceeded error in the schema change purge results in no
	// retry attempts of the purge.
	if e := 2; attempts != e {
		t.Fatalf("%d retries, despite allowing only (schema change + reverse) = %d", attempts, e)
	}

	// The index doesn't exist
	if _, err := sqlDB.Query(
		`SELECT v from [email protected]`,
	); !testutils.IsError(err, "index .* not found") {
		t.Fatal(err)
	}

	// Read table descriptor.
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	tableDesc := desc.GetTable()

	// There is still a mutation hanging off of it.
	if e := 1; len(tableDesc.Mutations) != e {
		t.Fatalf("the table has %d instead of %d mutations", len(tableDesc.Mutations), e)
	}
	// The mutation is for a DROP.
//.........这里部分代码省略.........

// Test schema change backfills are not affected by various operations
// that run simultaneously.
func TestRaceWithBackfill(t *testing.T) {
	defer leaktest.AfterTest(t)()

	// Disable asynchronous schema change execution to allow synchronous path
	// to trigger start of backfill notification.
	var backfillNotification chan bool
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs = base.TestingKnobs{
		SQLExecutor: &csql.ExecutorTestingKnobs{
			SchemaChangersStartBackfillNotification: func() error {
				if backfillNotification != nil {
					// Close channel to notify that the backfill has started.
					close(backfillNotification)
				}
				return nil
			},
		},
		SQLSchemaChangeManager: &csql.SchemaChangeManagerTestingKnobs{
			AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
		},
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k INT PRIMARY KEY, v INT, pi DECIMAL DEFAULT (DECIMAL '3.14'));
CREATE UNIQUE INDEX vidx ON t.test (v);
`); err != nil {
		t.Fatal(err)
	}

	// Bulk insert.
	maxValue := 4000
	insert := fmt.Sprintf(`INSERT INTO t.test VALUES (%d, %d)`, 0, maxValue)
	for i := 1; i <= maxValue; i++ {
		insert += fmt.Sprintf(` ,(%d, %d)`, i, maxValue-i)
	}
	if _, err := sqlDB.Exec(insert); err != nil {
		t.Fatal(err)
	}

	// Read table descriptor for version.
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	tableDesc := desc.GetTable()
	tablePrefix := roachpb.Key(keys.MakeTablePrefix(uint32(tableDesc.ID)))
	tableEnd := tablePrefix.PrefixEnd()
	// number of keys == 4 * number of rows; 3 columns and 1 index entry for
	// each row.
	if kvs, err := kvDB.Scan(tablePrefix, tableEnd, 0); err != nil {
		t.Fatal(err)
	} else if e := 4 * (maxValue + 1); len(kvs) != e {
		t.Fatalf("expected %d key value pairs, but got %d", e, len(kvs))
	}

	// Run some schema changes with operations.

	// Add column.
	backfillNotification = make(chan bool)
	runSchemaChangeWithOperations(
		t,
		sqlDB,
		kvDB,
		"ALTER TABLE t.test ADD COLUMN x DECIMAL DEFAULT (DECIMAL '1.4')",
		maxValue,
		5,
		descKey,
		backfillNotification)

	// Drop column.
	backfillNotification = make(chan bool)
	runSchemaChangeWithOperations(
		t,
		sqlDB,
		kvDB,
		"ALTER TABLE t.test DROP pi",
		maxValue,
		4,
		descKey,
		backfillNotification)

	// Add index.
	backfillNotification = make(chan bool)
	runSchemaChangeWithOperations(
		t,
		sqlDB,
//.........这里部分代码省略.........

func TestAsyncSchemaChanger(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	// Disable synchronous schema change execution so the asynchronous schema
	// changer executes all schema changes.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs = base.TestingKnobs{
		SQLExecutor: &csql.ExecutorTestingKnobs{
			SyncSchemaChangersFilter: func(tscc csql.TestingSchemaChangerCollection) {
				tscc.ClearSchemaChangers()
			},
		},
		SQLSchemaChangeManager: &csql.SchemaChangeManagerTestingKnobs{
			AsyncSchemaChangerExecQuickly: true,
		},
	}

	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k CHAR PRIMARY KEY, v CHAR);
INSERT INTO t.test VALUES ('a', 'b'), ('c', 'd');
`); err != nil {
		t.Fatal(err)
	}

	// Read table descriptor for version.
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	// A long running schema change operation runs through
	// a state machine that increments the version by 3.
	expectedVersion := desc.GetTable().Version + 3

	// Run some schema change
	if _, err := sqlDB.Exec(`
CREATE INDEX foo ON t.test (v)
`); err != nil {
		t.Fatal(err)
	}

	retryOpts := retry.Options{
		InitialBackoff: 20 * time.Millisecond,
		MaxBackoff:     200 * time.Millisecond,
		Multiplier:     2,
	}

	// Wait until index is created.
	for r := retry.Start(retryOpts); r.Next(); {
		if err := kvDB.GetProto(descKey, desc); err != nil {
			t.Fatal(err)
		}
		if len(desc.GetTable().Indexes) == 1 {
			break
		}
	}

	// Ensure that the indexes have been created.
	mTest := mutationTest{
		T:       t,
		kvDB:    kvDB,
		sqlDB:   sqlDB,
		descKey: descKey,
		desc:    desc,
	}
	indexQuery := `SELECT v FROM [email protected]`
	_ = mTest.checkQueryResponse(indexQuery, [][]string{{"b"}, {"d"}})

	// Ensure that the version has been incremented.
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	newVersion := desc.GetTable().Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
	}

	// Apply a schema change that only sets the UpVersion bit.
	expectedVersion = newVersion + 1

	if _, err := sqlDB.Exec(`
ALTER INDEX [email protected] RENAME TO ufo
`); err != nil {
		t.Fatal(err)
	}

//.........这里部分代码省略.........

func TestSchemaChangeProcess(t *testing.T) {
	defer leaktest.AfterTest(t)()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	// Disable external processing of mutations.
	ctx, _ := createTestServerContext()
	ctx.TestingKnobs.SQLSchemaChangeManager = &csql.SchemaChangeManagerTestingKnobs{
		AsyncSchemaChangerExecNotification: schemaChangeManagerDisabled,
	}
	server, sqlDB, kvDB := setupWithContext(t, &ctx)
	defer cleanup(server, sqlDB)
	var id = sqlbase.ID(keys.MaxReservedDescID + 2)
	var node = roachpb.NodeID(2)
	db := server.DB()
	leaseMgr := csql.NewLeaseManager(0, *db, hlc.NewClock(hlc.UnixNano), csql.LeaseManagerTestingKnobs{})
	changer := csql.NewSchemaChangerForTesting(id, 0, node, *db, leaseMgr)

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (k CHAR PRIMARY KEY, v CHAR, INDEX foo(v));
INSERT INTO t.test VALUES ('a', 'b'), ('c', 'd');
`); err != nil {
		t.Fatal(err)
	}

	// Read table descriptor for version.
	nameKey := sqlbase.MakeNameMetadataKey(keys.MaxReservedDescID+1, "test")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !gr.Exists() {
		t.Fatalf("Name entry %q does not exist", nameKey)
	}
	descKey := sqlbase.MakeDescMetadataKey(sqlbase.ID(gr.ValueInt()))
	desc := &sqlbase.Descriptor{}

	// Check that MaybeIncrementVersion doesn't increment the version
	// when the up_version bit is not set.
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
	expectedVersion := desc.GetTable().Version

	desc, err = changer.MaybeIncrementVersion()
	if err != nil {
		t.Fatal(err)
	}
	newVersion := desc.GetTable().Version
	if newVersion != expectedVersion {
		t.Fatalf("bad version; e = %d, v = %d", expectedVersion, newVersion)
	}
	isDone, err := changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if !isDone {
		t.Fatalf("table expected to not have an outstanding schema change: %v", desc.GetTable())
	}

	// Check that MaybeIncrementVersion increments the version
	// correctly.
	expectedVersion++
	desc.GetTable().UpVersion = true
	if e