Golang sql.MakeNameMetadataKey函數代碼示例

func TestInsert(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,
  CONSTRAINT a INDEX (k, v),
  CONSTRAINT b UNIQUE (v)
);
INSERT INTO t.kv VALUES ('c', 'e'), ('a', 'c'), ('b', 'd');
`); err != nil {
		t.Fatal(err)
	}

	// The first `MaxReservedDescID` (plus 0) are set aside.
	nameKey := sql.MakeNameMetadataKey(sql.MaxReservedDescID+1, "kv")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}

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

	descKey := sql.MakeDescMetadataKey(sql.ID(gr.ValueInt()))
	desc := sql.TableDescriptor{}
	if err := kvDB.GetProto(descKey, &desc); err != nil {
		t.Fatal(err)
	}

	var tablePrefix []byte
	tablePrefix = append(tablePrefix, keys.TableDataPrefix...)
	tablePrefix = encoding.EncodeUvarint(tablePrefix, uint64(desc.ID))

	tableStartKey := proto.Key(tablePrefix)
	tableEndKey := tableStartKey.PrefixEnd()
	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 12; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	// Insert that will fail after the index `a` is written.
	if _, err := sqlDB.Exec(`INSERT INTO t.kv VALUES ('d', 'd')`); !testutils.IsError(err, "duplicate key value .* violates unique constraint") {
		t.Fatalf("unexpected error %s", err)
	}

	// Verify nothing was written.
	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 12; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}
}

func TestDelete(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,
  CONSTRAINT a UNIQUE (v)
);
INSERT INTO t.kv VALUES ('c', 'e'), ('a', 'c'), ('b', 'd');
`); err != nil {
		t.Fatal(err)
	}

	// The first `MaxReservedDescID` (plus 0) are set aside.
	nameKey := sql.MakeNameMetadataKey(sql.MaxReservedDescID+1, "kv")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}

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

	descKey := sql.MakeDescMetadataKey(sql.ID(gr.ValueInt()))
	desc := sql.TableDescriptor{}
	if err := kvDB.GetProto(descKey, &desc); err != nil {
		t.Fatal(err)
	}

	var tablePrefix []byte
	tablePrefix = append(tablePrefix, keys.TableDataPrefix...)
	tablePrefix = encoding.EncodeUvarint(tablePrefix, uint64(desc.ID))

	tableStartKey := proto.Key(tablePrefix)
	tableEndKey := tableStartKey.PrefixEnd()
	if kvs, err := kvDB.Scan(tableStartKey, tableEndKey, 0); err != nil {
		t.Fatal(err)
	} else if l := 9; len(kvs) != l {
		t.Fatalf("expected %d key value pairs, but got %d", l, len(kvs))
	}

	if _, err := sqlDB.Exec(`DELETE FROM t.kv`); 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))
	}
}

// TestDescriptorCache populates the system config with fake entries
// and verifies that the cache uses them.
func TestDescriptorCache(t *testing.T) {
	defer leaktest.AfterTest(t)
	s, sqlDB, _ := setup(t)
	defer cleanup(s, sqlDB)

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

	// Create two tables. We'll be populating them with different data.
	if _, err := sqlDB.Exec(`CREATE TABLE test.test1 (k INT PRIMARY KEY, v INT)`); err != nil {
		t.Fatal(err)
	}
	if _, err := sqlDB.Exec(`CREATE TABLE test.test2 (k INT PRIMARY KEY, v INT)`); err != nil {
		t.Fatal(err)
	}

	// Put some data into each table. test1 has one row, test2 has two.
	if _, err := sqlDB.Exec(`INSERT INTO test.test1 VALUES (1, 1)`); err != nil {
		t.Fatal(err)
	}
	if _, err := sqlDB.Exec(`INSERT INTO test.test2 VALUES (2, 2), (3, 3)`); err != nil {
		t.Fatal(err)
	}

	// Wait for system config load.
	cfg, err := forceNewConfig(t, s)
	if err != nil {
		t.Fatalf("failed to get latest system config: %s", err)
	}

	dbID := keys.MaxReservedDescID + 1
	test1NameKey := sql.MakeNameMetadataKey(sql.ID(dbID), "test1")
	test2NameKey := sql.MakeNameMetadataKey(sql.ID(dbID), "test2")
	test1Index, ok := cfg.GetIndex(test1NameKey)
	if !ok {
		t.Fatalf("%s not found", test1NameKey)
	}

	test2Index, ok := cfg.GetIndex(test2NameKey)
	if !ok {
		t.Fatalf("%s not found", test2NameKey)
	}

	// Swap the namespace entries for the 'test1' and 'test2' tables in the system config.
	// This means that "test.test1" will resolve to the object ID for test2, and vice-versa.
	cfg.Values[test1Index].Value, cfg.Values[test2Index].Value =
		cfg.Values[test2Index].Value, cfg.Values[test1Index].Value
	// Gossip it and wait. We increment the fake descriptor in the system config and
	// wait for the callback to have it.
	configID++
	configDesc := sql.DatabaseDescriptor{
		Name:       "sentinel",
		ID:         configID,
		Privileges: &sql.PrivilegeDescriptor{},
	}
	raw, err := proto.Marshal(&configDesc)
	if err != nil {
		t.Fatal(err)
	}
	configDescIndex, ok := cfg.GetIndex(configDescKey)
	if !ok {
		t.Fatalf("%s not found", configDescKey)
	}
	cfg.Values[configDescIndex].Value.SetBytes(raw)
	if err := s.Gossip().AddInfoProto(gossip.KeySystemConfig, cfg, 0); err != nil {
		t.Fatal(err)
	}

	if _, err := waitForConfigChange(t, s); err != nil {
		t.Fatal(err)
	}

	// Pfeww. That was tedious. Now count the number of entries in each table.
	// We just waited for the config, so the cache should have it.
	// test1 was hacked to point to test2 which has two entries.
	count := 0
	if err := sqlDB.QueryRow(`SELECT COUNT(*) FROM test.test1`).Scan(&count); err != nil {
		t.Fatal(err)
	}
	if e := 2; count != e {
		t.Errorf("Bad number of rows from hacked test1, expected %d, got %d", e, count)
	}
	// test2 was hacked to point to test1 which has one entry.
	if err := sqlDB.QueryRow(`SELECT COUNT(*) FROM test.test2`).Scan(&count); err != nil {
		t.Fatal(err)
	}
	if e := 1; count != e {
		t.Errorf("Bad number of rows from hacked test2, expected %d, got %d", e, count)
	}

	// Now try again without caching.
	sql.TestingDisableDescriptorCache = true
	defer func() { sql.TestingDisableDescriptorCache = false }()
	if err := sqlDB.QueryRow(`SELECT COUNT(*) FROM test.test1`).Scan(&count); err != nil {
		t.Fatal(err)
	}
	if e := 1; count != e {
//.........這裏部分代碼省略.........

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

	expectedCounter := int64(keys.MaxReservedDescID + 1)

	// Test values before creating the database.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	// Database name.
	nameKey := sql.MakeNameMetadataKey(keys.RootNamespaceID, "test")
	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatal("expected non-existing key")
	}

	// Write a descriptor key that will interfere with database creation.
	dbDescKey := sql.MakeDescMetadataKey(sql.ID(expectedCounter))
	dbDesc := &sql.Descriptor{
		Union: &sql.Descriptor_Database{
			Database: &sql.DatabaseDescriptor{
				Name:       "sentinel",
				ID:         sql.ID(expectedCounter),
				Privileges: &sql.PrivilegeDescriptor{},
			},
		},
	}
	if err := kvDB.CPut(dbDescKey, dbDesc, nil); err != nil {
		t.Fatal(err)
	}

	// Database creation should fail, and nothing should have been written.
	if _, err := sqlDB.Exec(`CREATE DATABASE test`); !testutils.IsError(err, "unexpected value") {
		t.Fatalf("unexpected error %s", err)
	}

	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	start := roachpb.Key(keys.MakeTablePrefix(uint32(keys.NamespaceTableID)))
	if kvs, err := kvDB.Scan(start, start.PrefixEnd(), 0); err != nil {
		t.Fatal(err)
	} else {
		if a, e := len(kvs), server.GetBootstrapSchema().DescriptorCount(); a != e {
			t.Fatalf("expected %d keys to have been written, found %d keys", e, a)
		}
	}

	// Remove the junk; allow database creation to proceed.
	if err := kvDB.Del(dbDescKey); err != nil {
		t.Fatal(err)
	}

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

	// Check keys again.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	// Database name.
	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatal("key is missing")
	}

	// database descriptor.
	if gr, err := kvDB.Get(dbDescKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatal("key is missing")
	}

	// Now try to create it again. We should fail, but not increment the counter.
	if _, err := sqlDB.Exec(`CREATE DATABASE test`); err == nil {
		t.Fatal("failure expected")
	}

	// Check keys again.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
//.........這裏部分代碼省略.........

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.
	defer csql.TestDisableAsyncSchemaChangeExec()()
	server, sqlDB, kvDB := setup(t)
	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 := csql.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 := csql.MakeDescMetadataKey(csql.ID(gr.ValueInt()))
	desc := &csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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", csql.DescriptorMutation{Direction: csql.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)
	}
	// Noop.
	if _, err := sqlDB.Exec(`ALTER TABLE t.test DROP b`); err != nil {
//.........這裏部分代碼省略.........

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.
	defer csql.TestDisableAsyncSchemaChangeExec()()
	server, sqlDB, kvDB := setup(t)
	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 := csql.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 := csql.MakeDescMetadataKey(csql.ID(gr.ValueInt()))
	desc := &csql.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 * FROM [email protected]`
	// See the effect of the operations depending on the state.
	for _, state := range []csql.DescriptorMutation_State{csql.DescriptorMutation_DELETE_ONLY, csql.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", csql.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 == csql.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", csql.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 == csql.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"}})
		} else {
			// updating "x" -> "w" results in the index updating from "x" -> "w",
			// updating "z" -> "z" is a noop on the index.
//.........這裏部分代碼省略.........

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.
	defer csql.TestDisableAsyncSchemaChangeExec()()
	server, sqlDB, kvDB := setup(t)
	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 := csql.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 := csql.MakeDescMetadataKey(csql.ID(gr.ValueInt()))
	desc := &csql.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 []csql.DescriptorMutation_State{csql.DescriptorMutation_DELETE_ONLY, csql.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", csql.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", csql.DescriptorMutation{State: state})
		}
		// The table only contains columns "k" and "v".
		_ = mTest.checkQueryResponse(starQuery, [][]string{{"a", "z"}})

		// 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 == csql.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"}}
		}
		// Make column "i" a mutation.
		mTest.writeColumnMutation("i", csql.DescriptorMutation{State: state})
		// Insert a row into the table.
		if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ('c', 'x')`); err != nil {
			t.Fatal(err)
		}
//.........這裏部分代碼省略.........

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 := sql.MakeNameMetadataKey(sql.RootNamespaceID, "t")
	r, err := kvDB.Get(dbNameKey)
	if err != nil {
		t.Fatal(err)
	}
	if !r.Exists() {
		t.Fatalf(`database "t" does not exist`)
	}
	dbDescKey := sql.MakeDescMetadataKey(sql.ID(r.ValueInt()))
	dbDesc := sql.DatabaseDescriptor{}
	if err := kvDB.GetProto(dbDescKey, &dbDesc); err != nil {
		t.Fatal(err)
	}

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

	var tablePrefix []byte
	tablePrefix = append(tablePrefix, keys.TableDataPrefix...)
	tablePrefix = encoding.EncodeUvarint(tablePrefix, uint64(tbDesc.ID))

	tableStartKey := proto.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")
	}

	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 {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatalf("database descriptor still exists after database is dropped")
	}

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

func TestAsyncSchemaChanger(t *testing.T) {
	defer leaktest.AfterTest(t)
	// Disable synchronous schema change execution so
	// the asynchronous schema changer executes all
	// schema changes.
	defer csql.TestDisableSyncSchemaChangeExec()()
	// The descriptor changes made must have an immediate effect
	// so disable leases on tables.
	defer csql.TestDisableTableLeases()()
	server, sqlDB, kvDB := setup(t)
	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 := csql.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 := csql.MakeDescMetadataKey(csql.ID(gr.ValueInt()))
	desc := &csql.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 * 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)
	}

	for r := retry.Start(retryOpts); r.Next(); {
		// Ensure that the version gets incremented.
		if err := kvDB.GetProto(descKey, desc); err != nil {
			t.Fatal(err)
		}
		name := desc.GetTable().Indexes[0].Name
		if name != "ufo" {
			t.Fatalf("bad index name %s", name)
		}
		newVersion = desc.GetTable().Version
//.........這裏部分代碼省略.........

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.
	defer csql.TestDisableAsyncSchemaChangeExec()()
	server, sqlDB, kvDB := setup(t)
	defer cleanup(server, sqlDB)
	var id = csql.ID(keys.MaxReservedDescID + 2)
	var node = roachpb.NodeID(2)
	db := server.DB()
	leaseMgr := csql.NewLeaseManager(0, *db, hlc.NewClock(hlc.UnixNano))
	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 := csql.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 := csql.MakeDescMetadataKey(csql.ID(gr.ValueInt()))
	desc := &csql.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

	if err := changer.MaybeIncrementVersion(); err != nil {
		t.Fatal(err)
	}
	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)
	}
	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 err := kvDB.Put(descKey, desc); err != nil {
		t.Fatal(err)
	}
	isDone, err = changer.IsDone()
	if err != nil {
		t.Fatal(err)
	}
	if isDone {
		t.Fatalf("table expected to have an outstanding schema change: %v", desc.GetTable())
	}
	if err := changer.MaybeIncrementVersion(); err != nil {
		t.Fatal(err)
	}
	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)
	}
	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 RunStateMachineBeforeBackfill doesn't do anything
	// if there are no mutations queued.
	if err := changer.RunStateMachineBeforeBackfill(); err != nil {
		t.Fatal(err)
	}
	if err := kvDB.GetProto(descKey, desc); err != nil {
		t.Fatal(err)
	}
//.........這裏部分代碼省略.........

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 := sql.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 := sql.MakeDescMetadataKey(sql.ID(r.ValueInt()))
	desc := &sql.Descriptor{}
	if pErr := kvDB.GetProto(dbDescKey, desc); pErr != nil {
		t.Fatal(pErr)
	}
	dbDesc := desc.GetDatabase()

	tbNameKey := sql.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 := sql.MakeDescMetadataKey(sql.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 := proto.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 := sql.MakeZoneKey(tbDesc.ID)
	dbZoneKey := sql.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")
	}

	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 {
//.........這裏部分代碼省略.........

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 := sql.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 := sql.MakeDescMetadataKey(sql.ID(gr.ValueInt()))
	desc := &sql.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 != sql.DescriptorActive {
		t.Fatal("Index 'foo' is not active.")
	}
	indexPrefix := sql.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 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 := sql.MakeNameMetadataKey(keys.MaxReservedDescID+1, "kv")
	gr, err := kvDB.Get(nameKey)
	if err != nil {
		t.Fatal(err)
	}

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

	descKey := sql.MakeDescMetadataKey(sql.ID(gr.ValueInt()))
	desc := sql.TableDescriptor{}
	if err := kvDB.GetProto(descKey, &desc); err != nil {
		t.Fatal(err)
	}

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

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

	var tablePrefix []byte
	tablePrefix = append(tablePrefix, keys.TableDataPrefix...)
	tablePrefix = encoding.EncodeUvarint(tablePrefix, uint64(desc.ID))

	tableStartKey := proto.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)
	}

	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")
	}
}

// Test schema change backfills are not affected by various operations
// that run simultaneously.
func TestRaceWithBackfill(t *testing.T) {
	defer leaktest.AfterTest(t)()
	server, sqlDB, kvDB := setup(t)
	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.
	max_value := 2000
	insert := fmt.Sprintf(`INSERT INTO t.test VALUES (%d, %d)`, 0, max_value)
	for i := 1; i <= max_value; i++ {
		insert += fmt.Sprintf(` ,(%d, %d)`, i, max_value-i)
	}
	if _, err := sqlDB.Exec(insert); err != nil {
		t.Fatal(err)
	}

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

	// Run the schema changes in a separate goroutine.
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		start := timeutil.Now()
		// Start schema change that eventually runs a number of backfills.
		if _, err := sqlDB.Exec(`
BEGIN;
ALTER TABLE t.test ADD COLUMN x DECIMAL DEFAULT (DECIMAL '1.4');
CREATE UNIQUE INDEX foo ON t.test (v);
END;
`); err != nil {
			t.Error(err)
		}
		t.Logf("schema changes took %v", time.Since(start))
		wg.Done()
	}()

	// Wait until the backfills for the schema changes above have
	// started.
	util.SucceedsSoon(t, func() error {
		if pErr := kvDB.GetProto(descKey, desc); pErr != nil {
			t.Fatal(pErr)
		}
		if desc.GetTable().Version == version+2 {
			// Version upgrade has happened, backfills can proceed.
			return nil
		}
		return errors.New("version not updated")
	})

	// TODO(vivek): uncomment these inserts when #5817 is fixed.
	// Insert some new rows in the table while the backfills are running.
	//num_values := 5
	//for i := 0; i < num_values; i++ {
	//	t.Logf("inserting a new value into the table")
	//	if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES($1, $2)`, max_value+i+1, max_value+i+1); err != nil {
	//		t.Fatal(err)
	//	}
	//}

	// Renaming an index in the middle of the backfills will not affect
	// the backfills because the above schema changes have the schema change
	// lease on the table. All future schema changes have to wait in line for
	// the lease.
	if _, err := sqlDB.Exec(`
ALTER INDEX [email protected] RENAME TO bar;
`); err != nil {
		t.Fatal(err)
	}

	// Wait until schema changes have completed.
	wg.Wait()

	// Verify that the index over v is consistent.
	rows, err := sqlDB.Query(`SELECT v from [email protected]`)
	if err != nil {
		t.Fatal(err)
	}

//.........這裏部分代碼省略.........

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

	// The first `MaxReservedDescID` (plus 0) are set aside.
	expectedCounter := int64(sql.MaxReservedDescID + 1)

	// Test values before creating the database.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	// Database name.
	nameKey := sql.MakeNameMetadataKey(sql.RootNamespaceID, "test")
	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if gr.Exists() {
		t.Fatal("expected non-existing key")
	}

	// Write some junk that is going to interfere with table creation.
	dbDescKey := sql.MakeDescMetadataKey(sql.ID(expectedCounter))
	if err := kvDB.CPut(dbDescKey, "foo", nil); err != nil {
		t.Fatal(err)
	}

	// Table creation should fail, and nothing should have been written.
	if _, err := sqlDB.Exec(`CREATE DATABASE test`); !testutils.IsError(err, "unexpected value") {
		t.Fatalf("unexpected error %s", err)
	}

	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	if kvs, err := kvDB.Scan(keys.NameMetadataPrefix, keys.NameMetadataPrefix.PrefixEnd(), 0); err != nil {
		t.Fatal(err)
	} else {
		if a, e := len(kvs), 0; a != e {
			t.Fatalf("expected %d keys to have been written, found %d keys", e, a)
		}
	}

	// Remove the junk; allow table creation to proceed.
	if err := kvDB.Del(dbDescKey); err != nil {
		t.Fatal(err)
	}

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

	// Check keys again.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	// Database name.
	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatal("key is missing")
	}

	// database descriptor.
	if gr, err := kvDB.Get(dbDescKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatal("key is missing")
	}

	// Now try to create it again. We should fail, but not increment the counter.
	if _, err := sqlDB.Exec(`CREATE DATABASE test`); err == nil {
		t.Fatal("failure expected")
	}

	// Check keys again.
	// descriptor ID counter.
	if ir, err := kvDB.Get(keys.DescIDGenerator); err != nil {
		t.Fatal(err)
	} else if actual := ir.ValueInt(); actual != expectedCounter {
		t.Fatalf("expected descriptor ID == %d, got %d", expectedCounter, actual)
	}

	// Database name.
	if gr, err := kvDB.Get(nameKey); err != nil {
		t.Fatal(err)
	} else if !gr.Exists() {
		t.Fatal("key is missing")
	}
//.........這裏部分代碼省略.........