// sendRPC sends one or more RPCs to replicas from the supplied roachpb.Replica
// slice. Returns an RPC error if the request could not be sent. Note
// that the reply may contain a higher level error and must be checked in
// addition to the RPC error.
// The replicas are assume to have been ordered by preference, closer ones (if
// any) at the front.
func (ds *DistSender) sendRPC(
	ctx context.Context,
	rangeID roachpb.RangeID,
	replicas ReplicaSlice,
	ba roachpb.BatchRequest,
) (*roachpb.BatchResponse, error) {
	if len(replicas) == 0 {
		return nil, noNodeAddrsAvailError{}
	}

	// TODO(pmattis): This needs to be tested. If it isn't set we'll
	// still route the request appropriately by key, but won't receive
	// RangeNotFoundErrors.
	ba.RangeID = rangeID

	// Set RPC opts with stipulation that one of N RPCs must succeed.
	rpcOpts := SendOptions{
		SendNextTimeout:  ds.sendNextTimeout,
		Timeout:          base.NetworkTimeout,
		Context:          ctx,
		transportFactory: ds.transportFactory,
	}
	tracing.AnnotateTrace()
	defer tracing.AnnotateTrace()

	reply, err := ds.sendToReplicas(rpcOpts, rangeID, replicas, ba, ds.rpcContext)
	if err != nil {
		return nil, err
	}
	return reply, nil
}

// sendRPC sends one or more RPCs to replicas from the supplied roachpb.Replica
// slice. First, replicas which have gossiped addresses are corralled (and
// rearranged depending on proximity and whether the request needs to go to a
// leader) and then sent via Send, with requirement that one RPC to a server
// must succeed. Returns an RPC error if the request could not be sent. Note
// that the reply may contain a higher level error and must be checked in
// addition to the RPC error.
func (ds *DistSender) sendRPC(trace opentracing.Span, rangeID roachpb.RangeID, replicas ReplicaSlice,
	order orderingPolicy, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	if len(replicas) == 0 {
		return nil, roachpb.NewError(noNodeAddrsAvailError{})
	}

	// TODO(pmattis): This needs to be tested. If it isn't set we'll
	// still route the request appropriately by key, but won't receive
	// RangeNotFoundErrors.
	ba.RangeID = rangeID

	// Set RPC opts with stipulation that one of N RPCs must succeed.
	rpcOpts := SendOptions{
		Ordering:        order,
		SendNextTimeout: defaultSendNextTimeout,
		Timeout:         rpc.DefaultRPCTimeout,
		Trace:           trace,
	}
	tracing.AnnotateTrace()
	defer tracing.AnnotateTrace()

	reply, err := ds.rpcSend(rpcOpts, replicas, ba, ds.rpcContext)
	if err != nil {
		return nil, roachpb.NewError(err)
	}
	return reply.(*roachpb.BatchResponse), nil
}

// Run implements Runner.Run(). See comments there.
func (txn *Txn) Run(b *Batch) error {
	tracing.AnnotateTrace()
	defer tracing.AnnotateTrace()

	if err := b.prepare(); err != nil {
		return err
	}
	return sendAndFill(txn.send, b)
}

// RunWithResponse is a version of Run that returns the BatchResponse.
func (txn *Txn) RunWithResponse(b *Batch) (*roachpb.BatchResponse, *roachpb.Error) {
	tracing.AnnotateTrace()
	defer tracing.AnnotateTrace()

	if pErr := b.prepare(); pErr != nil {
		return nil, pErr
	}
	return sendAndFill(txn.send, b)
}

func (c *v3Conn) executeStatements(stmts string, params []parser.Datum, formatCodes []formatCode, sendDescription bool, limit int32) error {
	tracing.AnnotateTrace()
	results := c.executor.ExecuteStatements(c.session, stmts, params)

	tracing.AnnotateTrace()
	if results.Empty {
		// Skip executor and just send EmptyQueryResponse.
		c.writeBuf.initMsg(serverMsgEmptyQuery)
		return c.writeBuf.finishMsg(c.wr)
	}
	return c.sendResponse(results.ResultList, formatCodes, sendDescription, limit)
}

func (c *v3Conn) executeStatements(stmts string, params []parser.Datum, formatCodes []formatCode, sendDescription bool) error {
	tracing.AnnotateTrace()

	c.session.Database = c.opts.database

	// TODO(dt): this is a clumsy check better left to the actual parser. #3852
	if len(strings.TrimSpace(stmts)) == 0 {
		// Skip executor and just send EmptyQueryResponse.
		c.writeBuf.initMsg(serverMsgEmptyQuery)
		return c.writeBuf.finishMsg(c.wr)
	}

	resp, _, err := c.executor.ExecuteStatements(c.opts.user, c.session, stmts, params)
	if err != nil {
		return c.sendError(err.Error())
	}

	c.session.Reset()
	if err := c.session.Unmarshal(resp.Session); err != nil {
		return err
	}

	c.opts.database = c.session.Database
	return c.sendResponse(resp, formatCodes, sendDescription)
}

func (n *scanNode) Next() bool {
	tracing.AnnotateTrace()

	if n.pErr != nil {
		return false
	}

	if n.kvs == nil {
		if !n.initScan() {
			return false
		}
	}

	// All of the columns for a particular row will be grouped together. We loop
	// over the key/value pairs and decode the key to extract the columns encoded
	// within the key and the column ID. We use the column ID to lookup the
	// column and decode the value. All of these values go into a map keyed by
	// column name. When the index key changes we output a row containing the
	// current values.
	for {
		if n.maybeOutputRow() {
			return n.pErr == nil
		}
		if n.kvIndex == len(n.kvs) {
			return false
		}
		if !n.processKV(n.kvs[n.kvIndex]) {
			return false
		}
		n.kvIndex++
	}
}

// send runs the specified calls synchronously in a single batch and returns
// any errors. Returns a nil response for empty input (no requests).
func (db *DB) send(maxScanResults int64, reqs ...roachpb.Request) (
	*roachpb.BatchResponse, *roachpb.Error) {
	if len(reqs) == 0 {
		return nil, nil
	}

	ba := roachpb.BatchRequest{}
	ba.Add(reqs...)

	ba.MaxScanResults = maxScanResults
	if db.userPriority != 1 {
		ba.UserPriority = db.userPriority
	}

	tracing.AnnotateTrace()

	br, pErr := db.sender.Send(context.TODO(), ba)
	if pErr != nil {
		if log.V(1) {
			log.Infof("failed batch: %s", pErr)
		}
		return nil, pErr
	}
	return br, nil
}

func (n *scanNode) Next() bool {
	tracing.AnnotateTrace()

	if n.err != nil {
		return false
	}

	if !n.scanInitialized && !n.initScan() {
		// Hit error during initScan
		return false
	}

	if n.explain == explainDebug {
		return n.debugNext()
	}

	// We fetch one row at a time until we find one that passes the filter.
	for {
		n.row, n.err = n.fetcher.NextRow()
		if n.err != nil || n.row == nil {
			return false
		}
		passesFilter, err := runFilter(n.filter, n.planner.evalCtx)
		if err != nil {
			n.err = err
			return false
		}
		if passesFilter {
			return true
		}
	}
}

// send runs the specified calls synchronously in a single batch and returns
// any errors. Returns a nil response for empty input (no requests).
func (db *DB) send(maxScanResults int64, readConsistency roachpb.ReadConsistencyType,
	reqs ...roachpb.Request) (*roachpb.BatchResponse, *roachpb.Error) {
	if len(reqs) == 0 {
		return nil, nil
	}

	if readConsistency == roachpb.INCONSISTENT {
		for _, req := range reqs {
			if req.Method() != roachpb.Get && req.Method() != roachpb.Scan &&
				req.Method() != roachpb.ReverseScan {
				return nil, roachpb.NewErrorf("method %s not allowed with INCONSISTENT batch", req.Method)
			}
		}
	}

	ba := roachpb.BatchRequest{}
	ba.Add(reqs...)

	ba.MaxScanResults = maxScanResults
	if db.userPriority != 1 {
		ba.UserPriority = db.userPriority
	}
	ba.ReadConsistency = readConsistency

	tracing.AnnotateTrace()

	br, pErr := db.sender.Send(context.TODO(), ba)
	if pErr != nil {
		if log.V(1) {
			log.Infof("failed batch: %s", pErr)
		}
		return nil, pErr
	}
	return br, nil
}

// send runs the specified calls synchronously in a single batch and returns
// any errors. Returns (nil, nil) for an empty batch.
func (db *DB) send(ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	if len(ba.Requests) == 0 {
		return nil, nil
	}
	if ba.ReadConsistency == roachpb.INCONSISTENT {
		for _, ru := range ba.Requests {
			req := ru.GetInner()
			if req.Method() != roachpb.Get && req.Method() != roachpb.Scan &&
				req.Method() != roachpb.ReverseScan {
				return nil, roachpb.NewErrorf("method %s not allowed with INCONSISTENT batch", req.Method)
			}
		}
	}

	if db.ctx.UserPriority != 1 {
		ba.UserPriority = db.ctx.UserPriority
	}

	tracing.AnnotateTrace()

	br, pErr := db.sender.Send(context.TODO(), ba)
	if pErr != nil {
		if log.V(1) {
			log.Infof("failed batch: %s", pErr)
		}
		return nil, pErr
	}
	return br, nil
}

func (n *scanNode) Next() (bool, error) {
	tracing.AnnotateTrace()
	if !n.scanInitialized {
		if err := n.initScan(); err != nil {
			return false, nil
		}
	}

	if n.explain == explainDebug {
		return n.debugNext()
	}

	// We fetch one row at a time until we find one that passes the filter.
	for {
		var err error
		n.row, err = n.fetcher.NextRow()
		if err != nil || n.row == nil {
			return false, err
		}
		passesFilter, err := sqlbase.RunFilter(n.filter, n.p.evalCtx)
		if err != nil {
			return false, err
		}
		if passesFilter {
			return true, nil
		}
	}
}

func (u *updateNode) Next() (bool, error) {
	next, err := u.run.rows.Next()
	if !next {
		if err == nil {
			// We're done. Finish the batch.
			err = u.tw.finalize()
		}
		return false, err
	}

	if u.run.explain == explainDebug {
		return true, nil
	}

	tracing.AnnotateTrace()

	oldValues := u.run.rows.Values()

	// Our updated value expressions occur immediately after the plain
	// columns in the output.
	updateValues := oldValues[len(u.tw.ru.fetchCols):]
	oldValues = oldValues[:len(u.tw.ru.fetchCols)]

	u.checkHelper.loadRow(u.tw.ru.fetchColIDtoRowIndex, oldValues, false)
	u.checkHelper.loadRow(u.updateColsIdx, updateValues, true)
	if err := u.checkHelper.check(&u.p.evalCtx); err != nil {
		return false, err
	}

	// Ensure that the values honor the specified column widths.
	for i := range updateValues {
		if err := sqlbase.CheckValueWidth(u.tw.ru.updateCols[i], updateValues[i]); err != nil {
			return false, err
		}
	}

	// Update the row values.
	for i, col := range u.tw.ru.updateCols {
		val := updateValues[i]
		if !col.Nullable && val == parser.DNull {
			return false, sqlbase.NewNonNullViolationError(col.Name)
		}
	}

	newValues, err := u.tw.row(append(oldValues, updateValues...))
	if err != nil {
		return false, err
	}

	resultRow, err := u.rh.cookResultRow(newValues)
	if err != nil {
		return false, err
	}
	u.run.resultRow = resultRow

	return true, nil
}

func (c *v3Conn) executeStatements(
	ctx context.Context,
	stmts string,
	pinfo *parser.PlaceholderInfo,
	formatCodes []formatCode,
	sendDescription bool,
	limit int,
) error {
	tracing.AnnotateTrace()
	results := c.executor.ExecuteStatements(ctx, c.session, stmts, pinfo)

	tracing.AnnotateTrace()
	if results.Empty {
		// Skip executor and just send EmptyQueryResponse.
		c.writeBuf.initMsg(serverMsgEmptyQuery)
		return c.writeBuf.finishMsg(c.wr)
	}
	return c.sendResponse(results.ResultList, formatCodes, sendDescription, limit)
}

func (u *updateNode) Next() bool {
	if u.run.done || u.run.err != nil {
		return false
	}

	if !u.run.rows.Next() {
		// We're done. Finish the batch.
		err := u.tw.finalize()
		u.run.err = err
		u.run.done = true
		return false
	}

	tracing.AnnotateTrace()

	oldValues := u.run.rows.Values()

	// Our updated value expressions occur immediately after the plain
	// columns in the output.
	updateValues := oldValues[len(u.tableDesc.Columns):]
	oldValues = oldValues[:len(u.tableDesc.Columns)]

	// Ensure that the values honor the specified column widths.
	for i := range updateValues {
		if err := sqlbase.CheckValueWidth(u.updateCols[i], updateValues[i]); err != nil {
			u.run.err = err
			return false
		}
	}

	// Update the row values.
	for i, col := range u.updateCols {
		val := updateValues[i]
		if !col.Nullable && val == parser.DNull {
			u.run.err = fmt.Errorf("null value in column %q violates not-null constraint", col.Name)
			return false
		}
	}

	newValues, err := u.tw.row(append(oldValues, updateValues...))
	if err != nil {
		u.run.err = err
		return false
	}

	resultRow, err := u.rh.cookResultRow(newValues)
	if err != nil {
		u.run.err = err
		return false
	}
	u.run.resultRow = resultRow

	return true
}

// Update updates columns for a selection of rows from a table.
// Privileges: UPDATE and SELECT on table. We currently always use a select statement.
//   Notes: postgres requires UPDATE. Requires SELECT with WHERE clause with table.
//          mysql requires UPDATE. Also requires SELECT with WHERE clause with table.
// TODO(guanqun): need to support CHECK in UPDATE
func (p *planner) Update(n *parser.Update, desiredTypes []parser.Datum, autoCommit bool) (planNode, error) {
	tracing.AnnotateTrace()

	en, err := p.makeEditNode(n.Table, n.Returning, desiredTypes, autoCommit, privilege.UPDATE)
	if err != nil {
		return nil, err
	}

	exprs := make([]*parser.UpdateExpr, len(n.Exprs))
	for i, expr := range n.Exprs {
		// Replace the sub-query nodes.
		newExpr, err := p.replaceSubqueries(expr.Expr, len(expr.Names))
		if err != nil {
			return nil, err
		}
		exprs[i] = &parser.UpdateExpr{Tuple: expr.Tuple, Expr: newExpr, Names: expr.Names}
	}

	// Determine which columns we're inserting into.
	names, err := p.namesForExprs(exprs)
	if err != nil {
		return nil, err
	}

	updateCols, err := p.processColumns(en.tableDesc, names)
	if err != nil {
		return nil, err
	}

	defaultExprs, err := makeDefaultExprs(updateCols, &p.parser, p.evalCtx)
	if err != nil {
		return nil, err
	}

	var requestedCols []sqlbase.ColumnDescriptor
	if len(en.rh.exprs) > 0 || len(en.tableDesc.Checks) > 0 {
		// TODO(dan): This could be made tighter, just the rows needed for RETURNING
		// exprs.
		requestedCols = en.tableDesc.Columns
	}

	ru, err := makeRowUpdater(en.tableDesc, updateCols, requestedCols)
	if err != nil {
		return nil, err
	}
	tw := tableUpdater{ru: ru, autoCommit: autoCommit}

	tracing.AnnotateTrace()

	// Generate the list of select targets. We need to select all of the columns
	// plus we select all of the update expressions in case those expressions
	// reference columns (e.g. "UPDATE t SET v = v + 1"). Note that we flatten
	// expressions for tuple assignments just as we flattened the column names
	// above. So "UPDATE t SET (a, b) = (1, 2)" translates into select targets of
	// "*, 1, 2", not "*, (1, 2)".
	targets := sqlbase.ColumnsSelectors(ru.fetchCols)
	i := 0
	// Remember the index where the targets for exprs start.
	exprTargetIdx := len(targets)
	desiredTypesFromSelect := make([]parser.Datum, len(targets), len(targets)+len(exprs))
	for _, expr := range exprs {
		if expr.Tuple {
			switch t := expr.Expr.(type) {
			case (*parser.Tuple):
				for _, e := range t.Exprs {
					typ := updateCols[i].Type.ToDatumType()
					e := fillDefault(e, typ, i, defaultExprs)
					targets = append(targets, parser.SelectExpr{Expr: e})
					desiredTypesFromSelect = append(desiredTypesFromSelect, typ)
					i++
				}
			default:
				return nil, fmt.Errorf("cannot use this expression to assign multiple columns: %s", expr.Expr)
			}
		} else {
			typ := updateCols[i].Type.ToDatumType()
			e := fillDefault(expr.Expr, typ, i, defaultExprs)
			targets = append(targets, parser.SelectExpr{Expr: e})
			desiredTypesFromSelect = append(desiredTypesFromSelect, typ)
			i++
		}
	}

	rows, err := p.SelectClause(&parser.SelectClause{
		Exprs: targets,
		From:  []parser.TableExpr{n.Table},
		Where: n.Where,
	}, nil, nil, desiredTypesFromSelect)
	if err != nil {
		return nil, err
	}

	// ValArgs have their types populated in the above Select if they are part
	// of an expression ("SET a = 2 + $1") in the type check step where those
	// types are inferred. For the simpler case ("SET a = $1"), populate them
//.........这里部分代码省略.........

// Update updates columns for a selection of rows from a table.
// Privileges: UPDATE and SELECT on table. We currently always use a select statement.
//   Notes: postgres requires UPDATE. Requires SELECT with WHERE clause with table.
//          mysql requires UPDATE. Also requires SELECT with WHERE clause with table.
// TODO(guanqun): need to support CHECK in UPDATE
func (p *planner) Update(n *parser.Update, autoCommit bool) (planNode, *roachpb.Error) {
	tracing.AnnotateTrace()
	tableDesc, pErr := p.getAliasedTableLease(n.Table)
	if pErr != nil {
		return nil, pErr
	}

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

	// TODO(dan): Consider caching this on the TableDescriptor.
	primaryKeyCols := map[ColumnID]struct{}{}
	for _, id := range tableDesc.PrimaryIndex.ColumnIDs {
		primaryKeyCols[id] = struct{}{}
	}

	exprs := make([]parser.UpdateExpr, len(n.Exprs))
	for i, expr := range n.Exprs {
		exprs[i] = *expr
	}

	// Determine which columns we're inserting into.
	var names parser.QualifiedNames
	for i, expr := range exprs {
		newExpr, epErr := p.expandSubqueries(expr.Expr, len(expr.Names))
		if epErr != nil {
			return nil, epErr
		}
		exprs[i].Expr = newExpr

		if expr.Tuple {
			// TODO(pmattis): The distinction between Tuple and DTuple here is
			// irritating. We'll see a DTuple if the expression was a subquery that
			// has been evaluated. We'll see a Tuple in other cases.
			n := 0
			switch t := newExpr.(type) {
			case *parser.Tuple:
				n = len(t.Exprs)
			case parser.DTuple:
				n = len(t)
			default:
				return nil, roachpb.NewErrorf("unsupported tuple assignment: %T", newExpr)
			}
			if len(expr.Names) != n {
				return nil, roachpb.NewUErrorf("number of columns (%d) does not match number of values (%d)",
					len(expr.Names), n)
			}
		}
		names = append(names, expr.Names...)
	}
	cols, err := p.processColumns(tableDesc, names)
	if err != nil {
		return nil, roachpb.NewError(err)
	}

	// Set of columns being updated
	var primaryKeyColChange bool
	colIDSet := map[ColumnID]struct{}{}
	for _, c := range cols {
		colIDSet[c.ID] = struct{}{}
		if _, ok := primaryKeyCols[c.ID]; ok {
			primaryKeyColChange = true
		}
	}

	defaultExprs, err := makeDefaultExprs(cols, &p.parser, p.evalCtx)
	if err != nil {
		return nil, roachpb.NewError(err)
	}

	// Generate the list of select targets. We need to select all of the columns
	// plus we select all of the update expressions in case those expressions
	// reference columns (e.g. "UPDATE t SET v = v + 1"). Note that we flatten
	// expressions for tuple assignments just as we flattened the column names
	// above. So "UPDATE t SET (a, b) = (1, 2)" translates into select targets of
	// "*, 1, 2", not "*, (1, 2)".
	// TODO(radu): we only need to select columns necessary to generate primary and
	// secondary indexes keys, and columns needed by returningHelper.
	targets := tableDesc.allColumnsSelector()
	i := 0
	// Remember the index where the targets for exprs start.
	exprTargetIdx := len(targets)
	for _, expr := range exprs {
		if expr.Tuple {
			switch t := expr.Expr.(type) {
			case *parser.Tuple:
				for _, e := range t.Exprs {
					e = fillDefault(e, i, defaultExprs)
					targets = append(targets, parser.SelectExpr{Expr: e})
					i++
				}
			case parser.DTuple:
				for _, e := range t {
					targets = append(targets, parser.SelectExpr{Expr: e})
//.........这里部分代码省略.........

// Send implements the batch.Sender interface. It subdivides
// the Batch into batches admissible for sending (preventing certain
// illegal mixtures of requests), executes each individual part
// (which may span multiple ranges), and recombines the response.
// When the request spans ranges, it is split up and the corresponding
// ranges queried serially, in ascending order.
// In particular, the first write in a transaction may not be part of the first
// request sent. This is relevant since the first write is a BeginTransaction
// request, thus opening up a window of time during which there may be intents
// of a transaction, but no entry. Pushing such a transaction will succeed, and
// may lead to the transaction being aborted early.
func (ds *DistSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	tracing.AnnotateTrace()

	// In the event that timestamp isn't set and read consistency isn't
	// required, set the timestamp using the local clock.
	if ba.ReadConsistency == roachpb.INCONSISTENT && ba.Timestamp.Equal(roachpb.ZeroTimestamp) {
		ba.Timestamp = ds.clock.Now()
	}

	if ba.Txn != nil && len(ba.Txn.CertainNodes.Nodes) == 0 {
		// Ensure the local NodeID is marked as free from clock offset;
		// the transaction's timestamp was taken off the local clock.
		if nDesc := ds.getNodeDescriptor(); nDesc != nil {
			// TODO(tschottdorf): future refactoring should move this to txn
			// creation in TxnCoordSender, which is currently unaware of the
			// NodeID (and wraps *DistSender through client.Sender since it
			// also needs test compatibility with *LocalSender).
			//
			// Taking care below to not modify any memory referenced from
			// our BatchRequest which may be shared with others.
			// First, get a shallow clone of our txn (since that holds the
			// NodeList struct).
			txnShallow := *ba.Txn
			// Next, zero out the NodeList pointer. That makes sure that
			// if we had something of size zero but with capacity, we don't
			// re-use the existing space (which others may also use).
			txnShallow.CertainNodes.Nodes = nil
			txnShallow.CertainNodes.Add(nDesc.NodeID)
			ba.Txn = &txnShallow
		}
	}

	if len(ba.Requests) < 1 {
		panic("empty batch")
	}

	var rplChunks []*roachpb.BatchResponse
	parts := ba.Split(false /* don't split ET */)
	for len(parts) > 0 {
		part := parts[0]
		ba.Requests = part
		rpl, pErr, shouldSplitET := ds.sendChunk(ctx, ba)
		if shouldSplitET {
			// If we tried to send a single round-trip EndTransaction but
			// it looks like it's going to hit multiple ranges, split it
			// here and try again.
			if len(parts) != 1 {
				panic("EndTransaction not in last chunk of batch")
			}
			parts = ba.Split(true /* split ET */)
			if len(parts) != 2 {
				panic("split of final EndTransaction chunk resulted in != 2 parts")
			}
			continue
		}
		if pErr != nil {
			return nil, pErr
		}
		// Propagate transaction from last reply to next request. The final
		// update is taken and put into the response's main header.
		ba.Txn.Update(rpl.Header().Txn)
		rplChunks = append(rplChunks, rpl)
		parts = parts[1:]
	}

	reply := rplChunks[0]
	for _, rpl := range rplChunks[1:] {
		reply.Responses = append(reply.Responses, rpl.Responses...)
	}
	*reply.Header() = rplChunks[len(rplChunks)-1].BatchResponse_Header
	return reply, nil
}

// makePlan creates the query plan for a single SQL statement. The returned
// plan needs to be iterated over using planNode.Next() and planNode.Values()
// in order to retrieve matching rows. If autoCommit is true, the plan is
// allowed (but not required) to commit the transaction along with other KV
// operations.
//
// Note: The autoCommit parameter enables operations to enable the 1PC
// optimization. This is a bit hackish/preliminary at present.
func (p *planner) makePlan(stmt parser.Statement, autoCommit bool) (planNode, *roachpb.Error) {
	tracing.AnnotateTrace()

	// This will set the system DB trigger for transactions containing
	// DDL statements that have no effect, such as
	// `BEGIN; INSERT INTO ...; CREATE TABLE IF NOT EXISTS ...; COMMIT;`
	// where the table already exists. This will generate some false
	// refreshes, but that's expected to be quite rare in practice.
	if stmt.StatementType() == parser.DDL {
		p.txn.SetSystemConfigTrigger()
	}

	switch n := stmt.(type) {
	case *parser.AlterTable:
		return p.AlterTable(n)
	case *parser.BeginTransaction:
		pNode, err := p.BeginTransaction(n)
		return pNode, roachpb.NewError(err)
	case *parser.CommitTransaction:
		return p.CommitTransaction(n)
	case *parser.CreateDatabase:
		return p.CreateDatabase(n)
	case *parser.CreateIndex:
		return p.CreateIndex(n)
	case *parser.CreateTable:
		return p.CreateTable(n)
	case *parser.Delete:
		return p.Delete(n)
	case *parser.DropDatabase:
		return p.DropDatabase(n)
	case *parser.DropIndex:
		return p.DropIndex(n)
	case *parser.DropTable:
		return p.DropTable(n)
	case *parser.Explain:
		return p.Explain(n)
	case *parser.Grant:
		return p.Grant(n)
	case *parser.Insert:
		return p.Insert(n, autoCommit)
	case *parser.ParenSelect:
		return p.makePlan(n.Select, autoCommit)
	case *parser.RenameColumn:
		return p.RenameColumn(n)
	case *parser.RenameDatabase:
		return p.RenameDatabase(n)
	case *parser.RenameIndex:
		return p.RenameIndex(n)
	case *parser.RenameTable:
		return p.RenameTable(n)
	case *parser.Revoke:
		return p.Revoke(n)
	case *parser.RollbackTransaction:
		return p.RollbackTransaction(n)
	case *parser.Select:
		return p.Select(n)
	case *parser.Set:
		return p.Set(n)
	case *parser.SetTimeZone:
		return p.SetTimeZone(n)
	case *parser.SetTransaction:
		pNode, err := p.SetTransaction(n)
		return pNode, roachpb.NewError(err)
	case *parser.Show:
		return p.Show(n)
	case *parser.ShowColumns:
		return p.ShowColumns(n)
	case *parser.ShowDatabases:
		return p.ShowDatabases(n)
	case *parser.ShowGrants:
		return p.ShowGrants(n)
	case *parser.ShowIndex:
		return p.ShowIndex(n)
	case *parser.ShowTables:
		return p.ShowTables(n)
	case *parser.Truncate:
		return p.Truncate(n)
	case *parser.Update:
		return p.Update(n)
	case parser.Values:
		return p.Values(n)
	default:
		return nil, roachpb.NewErrorf("unknown statement type: %T", stmt)
	}
}

// Update updates columns for a selection of rows from a table.
// Privileges: UPDATE and SELECT on table. We currently always use a select statement.
//   Notes: postgres requires UPDATE. Requires SELECT with WHERE clause with table.
//          mysql requires UPDATE. Also requires SELECT with WHERE clause with table.
func (p *planner) Update(n *parser.Update, autoCommit bool) (planNode, *roachpb.Error) {
	tracing.AnnotateTrace()
	tableDesc, pErr := p.getAliasedTableLease(n.Table)
	if pErr != nil {
		return nil, pErr
	}

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

	// Determine which columns we're inserting into.
	var names parser.QualifiedNames
	for _, expr := range n.Exprs {
		var epErr *roachpb.Error
		expr.Expr, epErr = p.expandSubqueries(expr.Expr, len(expr.Names))
		if epErr != nil {
			return nil, epErr
		}

		if expr.Tuple {
			// TODO(pmattis): The distinction between Tuple and DTuple here is
			// irritating. We'll see a DTuple if the expression was a subquery that
			// has been evaluated. We'll see a Tuple in other cases.
			n := 0
			switch t := expr.Expr.(type) {
			case parser.Tuple:
				n = len(t)
			case parser.DTuple:
				n = len(t)
			default:
				return nil, roachpb.NewErrorf("unsupported tuple assignment: %T", expr.Expr)
			}
			if len(expr.Names) != n {
				return nil, roachpb.NewUErrorf("number of columns (%d) does not match number of values (%d)",
					len(expr.Names), n)
			}
		}
		names = append(names, expr.Names...)
	}
	cols, err := p.processColumns(tableDesc, names)
	if err != nil {
		return nil, roachpb.NewError(err)
	}

	// Set of columns being updated
	colIDSet := map[ColumnID]struct{}{}
	for _, c := range cols {
		colIDSet[c.ID] = struct{}{}
	}
	// Don't allow updating any column that is part of the primary key.
	for i, id := range tableDesc.PrimaryIndex.ColumnIDs {
		if _, ok := colIDSet[id]; ok {
			return nil, roachpb.NewUErrorf("primary key column %q cannot be updated", tableDesc.PrimaryIndex.ColumnNames[i])
		}
	}

	defaultExprs, err := p.makeDefaultExprs(cols)
	if err != nil {
		return nil, roachpb.NewError(err)
	}

	// Generate the list of select targets. We need to select all of the columns
	// plus we select all of the update expressions in case those expressions
	// reference columns (e.g. "UPDATE t SET v = v + 1"). Note that we flatten
	// expressions for tuple assignments just as we flattened the column names
	// above. So "UPDATE t SET (a, b) = (1, 2)" translates into select targets of
	// "*, 1, 2", not "*, (1, 2)".
	targets := tableDesc.allColumnsSelector()
	i := 0
	for _, expr := range n.Exprs {
		if expr.Tuple {
			switch t := expr.Expr.(type) {
			case parser.Tuple:
				for _, e := range t {
					e = fillDefault(e, i, defaultExprs)
					targets = append(targets, parser.SelectExpr{Expr: e})
					i++
				}
			case parser.DTuple:
				for _, e := range t {
					targets = append(targets, parser.SelectExpr{Expr: e})
					i++
				}
			}
		} else {
			e := fillDefault(expr.Expr, i, defaultExprs)
			targets = append(targets, parser.SelectExpr{Expr: e})
			i++
		}
	}

	tracing.AnnotateTrace()

	// Query the rows that need updating.
	rows, pErr := p.Select(&parser.Select{
//.........这里部分代码省略.........