Golang Batch.Del方法代碼示例

func runDel(cmd *cobra.Command, args []string) {
	if len(args) == 0 {
		cmd.Usage()
		return
	}

	count := len(args)

	keys := make([]string, 0, count)
	for i := 0; i < count; i++ {
		keys = append(keys, unquoteArg(args[i], true /* disallow system keys */))
	}

	kvDB := makeDBClient()
	if kvDB == nil {
		return
	}
	var b client.Batch
	for i := 0; i < count; i++ {
		b.Del(keys[i])
	}
	if err := kvDB.Run(&b); err != nil {
		fmt.Fprintf(osStderr, "delete failed: %s\n", err)
		osExit(1)
		return
	}
}

// deleteRow adds to the batch the kv operations necessary to delete a table row
// with the given values.
func (rd *rowDeleter) deleteRow(b *client.Batch, values []parser.Datum) error {
	if err := rd.fks.checkAll(values); err != nil {
		return err
	}

	primaryIndexKey, secondaryIndexEntries, err := rd.helper.encodeIndexes(rd.fetchColIDtoRowIndex, values)
	if err != nil {
		return err
	}

	for _, secondaryIndexEntry := range secondaryIndexEntries {
		if log.V(2) {
			log.Infof("Del %s", secondaryIndexEntry.Key)
		}
		b.Del(secondaryIndexEntry.Key)
	}

	// Delete the row.
	rd.startKey = roachpb.Key(primaryIndexKey)
	rd.endKey = rd.startKey.PrefixEnd()
	if log.V(2) {
		log.Infof("DelRange %s - %s", rd.startKey, rd.endKey)
	}
	b.DelRange(&rd.startKey, &rd.endKey, false)
	rd.startKey, rd.endKey = nil, nil

	return nil
}

// RenameDatabase renames the database.
// Privileges: security.RootUser user.
//   Notes: postgres requires superuser, db owner, or "CREATEDB".
//          mysql >= 5.1.23 does not allow database renames.
func (p *planner) RenameDatabase(n *parser.RenameDatabase) (planNode, error) {
	if n.Name == "" || n.NewName == "" {
		return nil, errEmptyDatabaseName
	}

	if p.session.User != security.RootUser {
		return nil, fmt.Errorf("only %s is allowed to rename databases", security.RootUser)
	}

	dbDesc, err := p.getDatabaseDesc(string(n.Name))
	if err != nil {
		return nil, err
	}
	if dbDesc == nil {
		return nil, databaseDoesNotExistError(string(n.Name))
	}

	if n.Name == n.NewName {
		// Noop.
		return &emptyNode{}, nil
	}

	// Now update the nameMetadataKey and the descriptor.
	descKey := sqlbase.MakeDescMetadataKey(dbDesc.GetID())
	dbDesc.SetName(string(n.NewName))

	if err := dbDesc.Validate(); err != nil {
		return nil, err
	}

	newKey := databaseKey{string(n.NewName)}.Key()
	oldKey := databaseKey{string(n.Name)}.Key()
	descID := dbDesc.GetID()
	descDesc := sqlbase.WrapDescriptor(dbDesc)

	b := client.Batch{}
	b.CPut(newKey, descID, nil)
	b.Put(descKey, descDesc)
	b.Del(oldKey)

	if err := p.txn.Run(&b); err != nil {
		if _, ok := err.(*roachpb.ConditionFailedError); ok {
			return nil, fmt.Errorf("the new database name %q already exists", string(n.NewName))
		}
		return nil, err
	}

	p.setTestingVerifyMetadata(func(systemConfig config.SystemConfig) error {
		if err := expectDescriptorID(systemConfig, newKey, descID); err != nil {
			return err
		}
		if err := expectDescriptor(systemConfig, descKey, descDesc); err != nil {
			return err
		}
		return expectDeleted(systemConfig, oldKey)
	})

	return &emptyNode{}, nil
}

// flush writes all dirty nodes and the tree to the transaction.
func (tc *treeContext) flush(b *client.Batch) {
	if tc.dirty {
		b.Put(keys.RangeTreeRoot, tc.tree)
	}
	for key, cachedNode := range tc.nodes {
		if cachedNode.dirty {
			if cachedNode.node == nil {
				b.Del(keys.RangeTreeNodeKey(roachpb.RKey(key)))
			} else {
				b.Put(keys.RangeTreeNodeKey(roachpb.RKey(key)), cachedNode.node)
			}
		}
	}
}

func runDel(cmd *cobra.Command, args []string) {
	if len(args) == 0 {
		mustUsage(cmd)
		return
	}

	var b client.Batch
	for _, arg := range args {
		b.Del(unquoteArg(arg, true /* disallow system keys */))
	}

	kvDB, stopper := makeDBClient()
	defer stopper.Stop()

	if err := kvDB.Run(&b); err != nil {
		panicf("delete failed: %s", err)
	}
}

// RenameDatabase renames the database.
// Privileges: "root" user.
//   Notes: postgres requires superuser, db owner, or "CREATEDB".
//          mysql >= 5.1.23 does not allow database renames.
func (p *planner) RenameDatabase(n *parser.RenameDatabase) (planNode, error) {
	if n.Name == "" || n.NewName == "" {
		return nil, errEmptyDatabaseName
	}

	if p.user != security.RootUser {
		return nil, fmt.Errorf("only %s is allowed to rename databases", security.RootUser)
	}

	dbDesc, err := p.getDatabaseDesc(string(n.Name))
	if err != nil {
		return nil, err
	}

	if n.Name == n.NewName {
		// Noop.
		return &valuesNode{}, nil
	}

	// Now update the nameMetadataKey and the descriptor.
	descKey := MakeDescMetadataKey(dbDesc.GetID())
	dbDesc.SetName(string(n.NewName))

	if err := dbDesc.Validate(); err != nil {
		return nil, err
	}

	b := client.Batch{}
	b.CPut(databaseKey{string(n.NewName)}.Key(), dbDesc.GetID(), nil)
	b.Put(descKey, dbDesc)
	b.Del(databaseKey{string(n.Name)}.Key())

	// Mark transaction as operating on the system DB.
	p.txn.SetSystemDBTrigger()
	if err := p.txn.Run(&b); err != nil {
		if _, ok := err.(*proto.ConditionFailedError); ok {
			return nil, fmt.Errorf("the new database name %q already exists", string(n.NewName))
		}
		return nil, err
	}

	return &valuesNode{}, nil
}

func runDel(cmd *cobra.Command, args []string) {
	if len(args) == 0 {
		cmd.Usage()
		return
	}

	var b client.Batch
	for _, arg := range args {
		b.Del(unquoteArg(arg, true /* disallow system keys */))
	}

	kvDB, stopper := makeDBClient()
	defer stopper.Stop()

	if err := kvDB.Run(&b); err != nil {
		fmt.Fprintf(osStderr, "delete failed: %s\n", err)
		osExit(1)
		return
	}
}

// RenameTable renames the table.
// Privileges: WRITE on database.
//   Notes: postgres requires the table owner.
//          mysql requires ALTER, DROP on the original table, and CREATE, INSERT
//          on the new table (and does not copy privileges over).
func (p *planner) RenameTable(n *parser.RenameTable) (planNode, error) {
	if n.NewName == "" {
		return nil, errEmptyTableName
	}

	if err := n.Name.NormalizeTableName(p.session.Database); err != nil {
		return nil, err
	}

	if n.Name.Table() == string(n.NewName) {
		// Noop.
		return &valuesNode{}, nil
	}

	dbDesc, err := p.getDatabaseDesc(n.Name.Database())
	if err != nil {
		return nil, err
	}

	tbKey := tableKey{dbDesc.ID, string(n.Name.Table())}.Key()

	// Check if table exists.
	gr, err := p.txn.Get(tbKey)
	if err != nil {
		return nil, err
	}
	if !gr.Exists() {
		if n.IfExists {
			// Noop.
			return &valuesNode{}, nil
		}
		// Key does not exist, but we want it to: error out.
		return nil, fmt.Errorf("table %q does not exist", n.Name.Table())
	}

	if err := p.checkPrivilege(dbDesc, privilege.WRITE); err != nil {
		return nil, err
	}

	tableDesc, err := p.getTableDesc(n.Name)
	if err != nil {
		return nil, err
	}

	tableDesc.SetName(string(n.NewName))

	newTbKey := tableKey{dbDesc.ID, string(n.NewName)}.Key()
	descKey := MakeDescMetadataKey(tableDesc.GetID())

	b := client.Batch{}
	b.Put(descKey, tableDesc)
	b.CPut(newTbKey, descKey, nil)
	b.Del(tbKey)
	if err := p.txn.Run(&b); err != nil {
		if _, ok := err.(*proto.ConditionFailedError); ok {
			return nil, fmt.Errorf("table name %q already exists", n.NewName)
		}
		return nil, err
	}

	return &valuesNode{}, nil
}

// RenameTable renames the table.
// Privileges: DROP on source table, CREATE on destination database.
//   Notes: postgres requires the table owner.
//          mysql requires ALTER, DROP on the original table, and CREATE, INSERT
//          on the new table (and does not copy privileges over).
func (p *planner) RenameTable(n *parser.RenameTable) (planNode, *roachpb.Error) {
	if err := n.NewName.NormalizeTableName(p.session.Database); err != nil {
		return nil, roachpb.NewError(err)
	}

	if n.NewName.Table() == "" {
		return nil, roachpb.NewError(errEmptyTableName)
	}

	if err := n.Name.NormalizeTableName(p.session.Database); err != nil {
		return nil, roachpb.NewError(err)
	}

	dbDesc, pErr := p.getDatabaseDesc(n.Name.Database())
	if pErr != nil {
		return nil, pErr
	}

	tbKey := tableKey{dbDesc.ID, n.Name.Table()}.Key()

	// Check if table exists.
	gr, pErr := p.txn.Get(tbKey)
	if pErr != nil {
		return nil, pErr
	}
	if !gr.Exists() {
		if n.IfExists {
			// Noop.
			return &valuesNode{}, nil
		}
		// Key does not exist, but we want it to: error out.
		return nil, roachpb.NewUErrorf("table %q does not exist", n.Name.Table())
	}

	targetDbDesc, pErr := p.getDatabaseDesc(n.NewName.Database())
	if pErr != nil {
		return nil, pErr
	}

	if pErr := p.checkPrivilege(targetDbDesc, privilege.CREATE); pErr != nil {
		return nil, pErr
	}

	if n.Name.Database() == n.NewName.Database() && n.Name.Table() == n.NewName.Table() {
		// Noop.
		return &valuesNode{}, nil
	}

	tableDesc, pErr := p.getTableDesc(n.Name)
	if pErr != nil {
		return nil, pErr
	}

	if pErr := p.checkPrivilege(tableDesc, privilege.DROP); pErr != nil {
		return nil, pErr
	}

	tableDesc.SetName(n.NewName.Table())
	tableDesc.ParentID = targetDbDesc.ID

	descKey := MakeDescMetadataKey(tableDesc.GetID())
	newTbKey := tableKey{targetDbDesc.ID, n.NewName.Table()}.Key()

	if err := tableDesc.Validate(); err != nil {
		return nil, roachpb.NewError(err)
	}

	descID := tableDesc.GetID()
	descDesc := wrapDescriptor(tableDesc)

	b := client.Batch{}
	b.Put(descKey, descDesc)
	b.CPut(newTbKey, descID, nil)
	b.Del(tbKey)

	if pErr := p.txn.Run(&b); pErr != nil {
		if _, ok := pErr.GoError().(*roachpb.ConditionFailedError); ok {
			return nil, roachpb.NewUErrorf("table name %q already exists", n.NewName.Table())
		}
		return nil, pErr
	}

	p.testingVerifyMetadata = func(systemConfig config.SystemConfig) error {
		if err := expectDescriptorID(systemConfig, newTbKey, descID); err != nil {
			return err
		}
		if err := expectDescriptor(systemConfig, descKey, descDesc); err != nil {
			return err
		}
		return expectDeleted(systemConfig, tbKey)
	}

	return &valuesNode{}, nil
}

// Delete deletes rows from a table.
// Privileges: WRITE and READ on table. We currently always use a SELECT statement.
//   Notes: postgres requires DELETE. Also requires SELECT for "USING" and "WHERE" with tables.
//          mysql requires DELETE. Also requires SELECT if a table is used in the "WHERE" clause.
func (p *planner) Delete(n *parser.Delete) (planNode, error) {
	tableDesc, err := p.getAliasedTableDesc(n.Table)
	if err != nil {
		return nil, err
	}

	if !tableDesc.HasPrivilege(p.user, parser.PrivilegeWrite) {
		return nil, fmt.Errorf("user %s does not have %s privilege on table %s",
			p.user, parser.PrivilegeWrite, tableDesc.Name)
	}

	// TODO(tamird,pmattis): avoid going through Select to avoid encoding
	// and decoding keys. Also, avoiding Select may provide more
	// convenient access to index keys which we are not currently
	// deleting.
	node, err := p.Select(&parser.Select{
		Exprs: parser.SelectExprs{
			&parser.StarExpr{TableName: &parser.QualifiedName{Base: parser.Name(tableDesc.Name)}},
		},
		From:  parser.TableExprs{n.Table},
		Where: n.Where,
	})
	if err != nil {
		return nil, err
	}

	// Construct a map from column ID to the index the value appears at within a
	// row.
	colIDtoRowIndex := map[structured.ID]int{}
	for i, name := range node.Columns() {
		c, err := tableDesc.FindColumnByName(name)
		if err != nil {
			return nil, err
		}
		colIDtoRowIndex[c.ID] = i
	}

	primaryIndex := tableDesc.PrimaryIndex
	primaryIndexKeyPrefix := structured.MakeIndexKeyPrefix(tableDesc.ID, primaryIndex.ID)

	b := client.Batch{}

	for node.Next() {
		if err := node.Err(); err != nil {
			return nil, err
		}
		values := node.Values()

		primaryIndexKeySuffix, _, err := encodeIndexKey(primaryIndex.ColumnIDs, colIDtoRowIndex, values, nil)
		if err != nil {
			return nil, err
		}
		primaryIndexKey := bytes.Join([][]byte{primaryIndexKeyPrefix, primaryIndexKeySuffix}, nil)

		// Delete the secondary indexes.
		secondaryIndexEntries, err := encodeSecondaryIndexes(tableDesc.ID, tableDesc.Indexes, colIDtoRowIndex, values, primaryIndexKeySuffix)
		if err != nil {
			return nil, err
		}

		for _, secondaryIndexEntry := range secondaryIndexEntries {
			if log.V(2) {
				log.Infof("Del %q", secondaryIndexEntry.key)
			}
			b.Del(secondaryIndexEntry.key)
		}

		// Delete the row.
		rowStartKey := proto.Key(primaryIndexKey)
		rowEndKey := rowStartKey.PrefixEnd()
		if log.V(2) {
			log.Infof("DelRange %q - %q", rowStartKey, rowEndKey)
		}
		b.DelRange(rowStartKey, rowEndKey)
	}

	if err := p.db.Run(&b); err != nil {
		return nil, err
	}

	// TODO(tamird/pmattis): return the number of affected rows
	return &valuesNode{}, nil
}

//.........這裏部分代碼省略.........
	// Secondary indexes needing updating.
	var indexes []IndexDescriptor
	for _, index := range tableDesc.Indexes {
		for _, id := range index.ColumnIDs {
			if _, ok := colIDSet[id]; ok {
				indexes = append(indexes, index)
				break
			}
		}
	}

	// Update all the rows.
	var b client.Batch
	for rows.Next() {
		rowVals := rows.Values()
		primaryIndexKey, _, err := encodeIndexKey(
			primaryIndex.ColumnIDs, colIDtoRowIndex, rowVals, primaryIndexKeyPrefix)
		if err != nil {
			return nil, err
		}
		// Compute the current secondary index key:value pairs for this row.
		secondaryIndexEntries, err := encodeSecondaryIndexes(
			tableDesc.ID, indexes, colIDtoRowIndex, rowVals)
		if err != nil {
			return nil, err
		}

		// Our updated value expressions occur immediately after the plain
		// columns in the output.
		newVals := rowVals[len(tableDesc.Columns):]
		// Update the row values.
		for i, col := range cols {
			val := newVals[i]
			if !col.Nullable && val == parser.DNull {
				return nil, fmt.Errorf("null value in column %q violates not-null constraint", col.Name)
			}
			rowVals[colIDtoRowIndex[col.ID]] = val
		}
		// Compute the new secondary index key:value pairs for this row.
		newSecondaryIndexEntries, err := encodeSecondaryIndexes(
			tableDesc.ID, indexes, colIDtoRowIndex, rowVals)
		if err != nil {
			return nil, err
		}
		// Update secondary indexes.
		for i, newSecondaryIndexEntry := range newSecondaryIndexEntries {
			secondaryIndexEntry := secondaryIndexEntries[i]
			if !bytes.Equal(newSecondaryIndexEntry.key, secondaryIndexEntry.key) {
				if log.V(2) {
					log.Infof("CPut %q -> %v", newSecondaryIndexEntry.key, newSecondaryIndexEntry.value)
				}
				b.CPut(newSecondaryIndexEntry.key, newSecondaryIndexEntry.value, nil)
				if log.V(2) {
					log.Infof("Del %q", secondaryIndexEntry.key)
				}
				b.Del(secondaryIndexEntry.key)
			}
		}

		// Add the new values.
		for i, val := range newVals {
			col := cols[i]

			primitive, err := convertDatum(col, val)
			if err != nil {
				return nil, err
			}

			key := MakeColumnKey(col.ID, primaryIndexKey)
			if primitive != nil {
				// We only output non-NULL values. Non-existent column keys are
				// considered NULL during scanning and the row sentinel ensures we know
				// the row exists.
				if log.V(2) {
					log.Infof("Put %q -> %v", key, val)
				}

				b.Put(key, primitive)
			} else {
				// The column might have already existed but is being set to NULL, so
				// delete it.
				if log.V(2) {
					log.Infof("Del %q", key)
				}

				b.Del(key)
			}
		}
	}

	if err := rows.Err(); err != nil {
		return nil, err
	}
	if err := p.txn.Run(&b); err != nil {
		return nil, convertBatchError(tableDesc, b, err)
	}

	// TODO(tamird/pmattis): return the number of affected rows.
	return &valuesNode{}, nil
}

func (p *planner) backfillBatch(b *client.Batch, oldTableDesc *TableDescriptor, mutationID MutationID) *roachpb.Error {
	var droppedColumnDescs []ColumnDescriptor
	var droppedIndexDescs []IndexDescriptor
	var newIndexDescs []IndexDescriptor
	// Collect the elements that are part of the mutation.
	for _, m := range oldTableDesc.Mutations {
		if m.MutationID != mutationID {
			// Mutations are applied in a FIFO order. Only apply the first set of
			// mutations if they have the mutation ID we're looking for.
			break
		}
		switch m.Direction {
		case DescriptorMutation_ADD:
			switch t := m.Descriptor_.(type) {
			case *DescriptorMutation_Column:
				// TODO(vivek): Add column to new columns and use it
				// to fill in default values.

			case *DescriptorMutation_Index:
				newIndexDescs = append(newIndexDescs, *t.Index)
			}

		case DescriptorMutation_DROP:
			switch t := m.Descriptor_.(type) {
			case *DescriptorMutation_Column:
				droppedColumnDescs = append(droppedColumnDescs, *t.Column)

			case *DescriptorMutation_Index:
				droppedIndexDescs = append(droppedIndexDescs, *t.Index)
			}
		}
	}

	// TODO(vivek): Break these backfill operations into chunks. All of them
	// will fail on big tables (see #3274).

	// Delete the entire dropped columns.
	// This used to use SQL UPDATE in the past to update the dropped
	// column to NULL; but a column in the process of being
	// dropped is placed in the table descriptor mutations, and
	// a SQL UPDATE of a column in mutations will fail.
	if len(droppedColumnDescs) > 0 {
		// Run a scan across the table using the primary key.
		start := roachpb.Key(MakeIndexKeyPrefix(oldTableDesc.ID, oldTableDesc.PrimaryIndex.ID))
		// Use a different batch to perform the scan.
		batch := &client.Batch{}
		batch.Scan(start, start.PrefixEnd(), 0)
		if pErr := p.txn.Run(batch); pErr != nil {
			return pErr
		}
		for _, result := range batch.Results {
			var sentinelKey roachpb.Key
			for _, kv := range result.Rows {
				if sentinelKey == nil || !bytes.HasPrefix(kv.Key, sentinelKey) {
					// Sentinel keys have a 0 suffix indicating 0 bytes of column
					// ID. Strip off that suffix to determine the prefix shared with the
					// other keys for the row.
					sentinelKey = stripColumnIDLength(kv.Key)
					for _, columnDesc := range droppedColumnDescs {
						// Delete the dropped column.
						colKey := keys.MakeColumnKey(sentinelKey, uint32(columnDesc.ID))
						if log.V(2) {
							log.Infof("Del %s", colKey)
						}
						b.Del(colKey)
					}
				}
			}
		}
	}

	for _, indexDescriptor := range droppedIndexDescs {
		indexPrefix := MakeIndexKeyPrefix(oldTableDesc.ID, indexDescriptor.ID)

		// Delete the index.
		indexStartKey := roachpb.Key(indexPrefix)
		indexEndKey := indexStartKey.PrefixEnd()
		if log.V(2) {
			log.Infof("DelRange %s - %s", indexStartKey, indexEndKey)
		}
		b.DelRange(indexStartKey, indexEndKey)
	}

	if len(newIndexDescs) > 0 {
		// Get all the rows affected.
		// TODO(vivek): Avoid going through Select.
		// TODO(tamird): Support partial indexes?
		// Use a scanNode with SELECT to pass in a TableDescriptor
		// to the SELECT without needing to use a parser.QualifiedName,
		// because we want to run schema changes from a gossip feed of
		// table IDs.
		scan := &scanNode{
			planner: p,
			txn:     p.txn,
			desc:    oldTableDesc,
		}
		scan.initDescDefaults()
		rows, pErr := p.selectIndex(&selectNode{}, scan, nil, false)
		if pErr != nil {
			return pErr
//.........這裏部分代碼省略.........

// updateRow adds to the batch the kv operations necessary to update a table row
// with the given values.
//
// The row corresponding to oldValues is updated with the ones in updateValues.
// Note that updateValues only contains the ones that are changing.
//
// The return value is only good until the next call to UpdateRow.
func (ru *rowUpdater) updateRow(
	b *client.Batch,
	oldValues []parser.Datum,
	updateValues []parser.Datum,
) ([]parser.Datum, error) {
	if len(oldValues) != len(ru.fetchCols) {
		return nil, util.Errorf("got %d values but expected %d", len(oldValues), len(ru.fetchCols))
	}
	if len(updateValues) != len(ru.updateCols) {
		return nil, util.Errorf("got %d values but expected %d", len(updateValues), len(ru.updateCols))
	}

	primaryIndexKey, secondaryIndexEntries, err := ru.helper.encodeIndexes(ru.fetchColIDtoRowIndex, oldValues)
	if err != nil {
		return nil, err
	}

	// Check that the new value types match the column types. This needs to
	// happen before index encoding because certain datum types (i.e. tuple)
	// cannot be used as index values.
	for i, val := range updateValues {
		if ru.marshalled[i], err = sqlbase.MarshalColumnValue(ru.updateCols[i], val); err != nil {
			return nil, err
		}
	}

	// Update the row values.
	copy(ru.newValues, oldValues)
	for i, updateCol := range ru.updateCols {
		ru.newValues[ru.fetchColIDtoRowIndex[updateCol.ID]] = updateValues[i]
	}

	newPrimaryIndexKey := primaryIndexKey
	rowPrimaryKeyChanged := false
	var newSecondaryIndexEntries []sqlbase.IndexEntry
	if ru.primaryKeyColChange {
		newPrimaryIndexKey, newSecondaryIndexEntries, err = ru.helper.encodeIndexes(ru.fetchColIDtoRowIndex, ru.newValues)
		if err != nil {
			return nil, err
		}
		rowPrimaryKeyChanged = !bytes.Equal(primaryIndexKey, newPrimaryIndexKey)
	} else {
		newSecondaryIndexEntries, err = sqlbase.EncodeSecondaryIndexes(
			ru.helper.tableDesc.ID, ru.helper.indexes, ru.fetchColIDtoRowIndex, ru.newValues)
		if err != nil {
			return nil, err
		}
	}

	if rowPrimaryKeyChanged {
		err := ru.rd.deleteRow(b, oldValues)
		if err != nil {
			return nil, err
		}
		err = ru.ri.insertRow(b, ru.newValues)
		return ru.newValues, err
	}

	// Update secondary indexes.
	for i, newSecondaryIndexEntry := range newSecondaryIndexEntries {
		secondaryIndexEntry := secondaryIndexEntries[i]
		secondaryKeyChanged := !bytes.Equal(newSecondaryIndexEntry.Key, secondaryIndexEntry.Key)
		if secondaryKeyChanged {
			if log.V(2) {
				log.Infof("Del %s", secondaryIndexEntry.Key)
			}
			b.Del(secondaryIndexEntry.Key)
			// Do not update Indexes in the DELETE_ONLY state.
			if _, ok := ru.deleteOnlyIndex[i]; !ok {
				if log.V(2) {
					log.Infof("CPut %s -> %v", newSecondaryIndexEntry.Key, newSecondaryIndexEntry.Value)
				}
				b.CPut(newSecondaryIndexEntry.Key, newSecondaryIndexEntry.Value, nil)
			}
		}
	}

	// Add the new values.
	for i, val := range updateValues {
		col := ru.updateCols[i]

		if ru.helper.columnInPK(col.ID) {
			// Skip primary key columns as their values are encoded in the row
			// sentinel key which is guaranteed to exist for as long as the row
			// exists.
			continue
		}

		ru.key = keys.MakeColumnKey(newPrimaryIndexKey, uint32(col.ID))
		if ru.marshalled[i].RawBytes != nil {
			// We only output non-NULL values. Non-existent column keys are
			// considered NULL during scanning and the row sentinel ensures we know
			// the row exists.
//.........這裏部分代碼省略.........

// Delete deletes rows from a table.
// Privileges: DELETE and SELECT on table. We currently always use a SELECT statement.
//   Notes: postgres requires DELETE. Also requires SELECT for "USING" and "WHERE" with tables.
//          mysql requires DELETE. Also requires SELECT if a table is used in the "WHERE" clause.
func (p *planner) Delete(n *parser.Delete) (planNode, error) {
	tableDesc, err := p.getAliasedTableDesc(n.Table, false /* !allowCache */)
	if err != nil {
		return nil, err
	}

	if err := p.checkPrivilege(tableDesc, privilege.DELETE); err != nil {
		return nil, err
	}

	// TODO(tamird,pmattis): avoid going through Select to avoid encoding
	// and decoding keys. Also, avoiding Select may provide more
	// convenient access to index keys which we are not currently
	// deleting.
	rows, err := p.Select(&parser.Select{
		Exprs: parser.SelectExprs{parser.StarSelectExpr()},
		From:  parser.TableExprs{n.Table},
		Where: n.Where,
	})
	if err != nil {
		return nil, err
	}

	// Construct a map from column ID to the index the value appears at within a
	// row.
	colIDtoRowIndex := map[ColumnID]int{}
	for i, name := range rows.Columns() {
		c, err := tableDesc.FindColumnByName(name)
		if err != nil {
			return nil, err
		}
		colIDtoRowIndex[c.ID] = i
	}

	primaryIndex := tableDesc.PrimaryIndex
	primaryIndexKeyPrefix := MakeIndexKeyPrefix(tableDesc.ID, primaryIndex.ID)

	b := client.Batch{}
	result := &valuesNode{}
	for rows.Next() {
		rowVals := rows.Values()
		result.rows = append(result.rows, parser.DTuple(nil))

		primaryIndexKey, _, err := encodeIndexKey(
			primaryIndex.ColumnIDs, colIDtoRowIndex, rowVals, primaryIndexKeyPrefix)
		if err != nil {
			return nil, err
		}

		// Delete the secondary indexes.
		secondaryIndexEntries, err := encodeSecondaryIndexes(
			tableDesc.ID, tableDesc.Indexes, colIDtoRowIndex, rowVals)
		if err != nil {
			return nil, err
		}

		for _, secondaryIndexEntry := range secondaryIndexEntries {
			if log.V(2) {
				log.Infof("Del %s", prettyKey(secondaryIndexEntry.key, 0))
			}
			b.Del(secondaryIndexEntry.key)
		}

		// Delete the row.
		rowStartKey := roachpb.Key(primaryIndexKey)
		rowEndKey := rowStartKey.PrefixEnd()
		if log.V(2) {
			log.Infof("DelRange %s - %s", prettyKey(rowStartKey, 0), prettyKey(rowEndKey, 0))
		}
		b.DelRange(rowStartKey, rowEndKey)
	}

	if err := rows.Err(); err != nil {
		return nil, err
	}

	if err := p.txn.Run(&b); err != nil {
		return nil, err
	}

	return result, nil
}

func (p *planner) backfillBatch(b *client.Batch, oldTableDesc, newTableDesc *TableDescriptor) error {
	var droppedColumnDescs []ColumnDescriptor
	var droppedIndexDescs []IndexDescriptor
	var newIndexDescs []IndexDescriptor
	for _, m := range oldTableDesc.Mutations {
		switch m.Direction {
		case DescriptorMutation_ADD:
			switch t := m.Descriptor_.(type) {
			case *DescriptorMutation_Column:
				// TODO(vivek): Add column to new columns and use it
				// to fill in default values.

			case *DescriptorMutation_Index:
				newIndexDescs = append(newIndexDescs, *t.Index)
			}

		case DescriptorMutation_DROP:
			switch t := m.Descriptor_.(type) {
			case *DescriptorMutation_Column:
				droppedColumnDescs = append(droppedColumnDescs, *t.Column)

			case *DescriptorMutation_Index:
				droppedIndexDescs = append(droppedIndexDescs, *t.Index)
			}
		}
	}

	// TODO(vivek): Break these backfill operations into chunks. All of them
	// will fail on big tables.

	// Delete the entire dropped columns.
	// This used to use SQL UPDATE in the past to update the dropped
	// column to NULL; but a column in the process of being
	// dropped is placed in the table descriptor mutations, and
	// a SQL UPDATE of a column in mutations will fail.
	if len(droppedColumnDescs) > 0 {
		// Run a scan across the table using the primary key.
		start := roachpb.Key(MakeIndexKeyPrefix(newTableDesc.ID, newTableDesc.PrimaryIndex.ID))
		// Use a different batch to perform the scan.
		batch := &client.Batch{}
		batch.Scan(start, start.PrefixEnd(), 0)
		if err := p.txn.Run(batch); err != nil {
			return err
		}
		for _, result := range batch.Results {
			var sentinelKey roachpb.Key
			for _, kv := range result.Rows {
				if sentinelKey == nil || !bytes.HasPrefix(kv.Key, sentinelKey) {
					// Sentinel keys have a 0 suffix indicating 0 bytes of column
					// ID. Strip off that suffix to determine the prefix shared with the
					// other keys for the row.
					sentinelKey = stripColumnIDLength(kv.Key)
					for _, columnDesc := range droppedColumnDescs {
						// Delete the dropped column.
						colKey := keys.MakeColumnKey(sentinelKey, uint32(columnDesc.ID))
						if log.V(2) {
							log.Infof("Del %s", colKey)
						}
						b.Del(colKey)
					}
				}
			}
		}
	}

	for _, indexDescriptor := range droppedIndexDescs {
		indexPrefix := MakeIndexKeyPrefix(newTableDesc.ID, indexDescriptor.ID)

		// Delete the index.
		indexStartKey := roachpb.Key(indexPrefix)
		indexEndKey := indexStartKey.PrefixEnd()
		if log.V(2) {
			log.Infof("DelRange %s - %s", indexStartKey, indexEndKey)
		}
		b.DelRange(indexStartKey, indexEndKey)
	}

	if len(newIndexDescs) > 0 {
		// Get all the rows affected.
		// TODO(vivek): Avoid going through Select.
		// TODO(tamird): Support partial indexes?
		// Use a scanNode with SELECT to pass in a TableDescriptor
		// to the SELECT without needing to use a parser.QualifiedName,
		// because we want to run schema changes from a gossip feed of
		// table IDs.
		scan := &scanNode{
			planner: p,
			txn:     p.txn,
			desc:    oldTableDesc,
		}
		scan.initDescDefaults()
		rows, err := p.selectWithScan(scan, &parser.Select{Exprs: oldTableDesc.allColumnsSelector()})
		if err != nil {
			return err
		}

		// Construct a map from column ID to the index the value appears at within a
		// row.
		colIDtoRowIndex, err := makeColIDtoRowIndex(rows, oldTableDesc)
		if err != nil {
//.........這裏部分代碼省略.........