func makeDefaultExprs(
	cols []sqlbase.ColumnDescriptor, parse *parser.Parser, evalCtx *parser.EvalContext,
) ([]parser.TypedExpr, error) {
	// Check to see if any of the columns have DEFAULT expressions. If there
	// are no DEFAULT expressions, we don't bother with constructing the
	// defaults map as the defaults are all NULL.
	haveDefaults := false
	for _, col := range cols {
		if col.DefaultExpr != nil {
			haveDefaults = true
			break
		}
	}
	if !haveDefaults {
		return nil, nil
	}

	// Build the default expressions map from the parsed SELECT statement.
	defaultExprs := make([]parser.TypedExpr, 0, len(cols))
	exprStrings := make([]string, 0, len(cols))
	for _, col := range cols {
		if col.DefaultExpr != nil {
			exprStrings = append(exprStrings, *col.DefaultExpr)
		}
	}
	exprs, err := parser.ParseExprsTraditional(exprStrings)
	if err != nil {
		return nil, err
	}

	defExprIdx := 0
	for _, col := range cols {
		if col.DefaultExpr == nil {
			defaultExprs = append(defaultExprs, parser.DNull)
			continue
		}
		expr := exprs[defExprIdx]
		typedExpr, err := parser.TypeCheck(expr, nil, col.Type.ToDatumType())
		if err != nil {
			return nil, err
		}
		if typedExpr, err = parse.NormalizeExpr(evalCtx, typedExpr); err != nil {
			return nil, err
		}
		defaultExprs = append(defaultExprs, typedExpr)
		defExprIdx++
	}
	return defaultExprs, nil
}

func (eh *exprHelper) init(
	expr Expression, types []sqlbase.ColumnType_Kind, evalCtx *parser.EvalContext,
) error {
	if expr.Expr == "" {
		return nil
	}
	eh.types = types
	eh.evalCtx = evalCtx
	eh.vars = parser.MakeIndexedVarHelper(eh, len(types))
	var err error
	eh.expr, err = processExpression(expr, &eh.vars)
	if err != nil {
		return err
	}
	var p parser.Parser
	if p.AggregateInExpr(eh.expr, evalCtx.SearchPath) {
		return errors.Errorf("expression '%s' has aggregate", eh.expr)
	}
	return nil
}

// Prepare returns the result types of the given statement. pinfo may
// contain partial type information for placeholders. Prepare will
// populate the missing types. The column result types are returned (or
// nil if there are no results).
func (e *Executor) Prepare(
	query string, session *Session, pinfo parser.PlaceholderTypes,
) (ResultColumns, error) {
	log.VEventf(session.Ctx(), 2, "preparing: %s", query)
	var p parser.Parser
	stmts, err := p.Parse(query, parser.Syntax(session.Syntax))
	if err != nil {
		return nil, err
	}
	switch len(stmts) {
	case 0:
		return nil, nil
	case 1:
		// ignore
	default:
		return nil, errors.Errorf("expected 1 statement, but found %d", len(stmts))
	}
	stmt := stmts[0]
	if err = pinfo.ProcessPlaceholderAnnotations(stmt); err != nil {
		return nil, err
	}
	protoTS, err := isAsOf(&session.planner, stmt, e.cfg.Clock.Now())
	if err != nil {
		return nil, err
	}

	session.planner.resetForBatch(e)
	session.planner.semaCtx.Placeholders.SetTypes(pinfo)
	session.planner.evalCtx.PrepareOnly = true

	// Prepare needs a transaction because it needs to retrieve db/table
	// descriptors for type checking.
	// TODO(andrei): is this OK? If we're preparing as part of a SQL txn, how do
	// we check that they're reading descriptors consistent with the txn in which
	// they'll be used?
	txn := client.NewTxn(session.Ctx(), *e.cfg.DB)
	txn.Proto.Isolation = session.DefaultIsolationLevel
	session.planner.setTxn(txn)
	defer session.planner.setTxn(nil)

	if protoTS != nil {
		session.planner.avoidCachedDescriptors = true
		defer func() {
			session.planner.avoidCachedDescriptors = false
		}()

		setTxnTimestamps(txn, *protoTS)
	}

	plan, err := session.planner.prepare(stmt)
	if err != nil {
		return nil, err
	}
	if plan == nil {
		return nil, nil
	}
	defer plan.Close()
	cols := plan.Columns()
	for _, c := range cols {
		if err := checkResultType(c.Typ); err != nil {
			return nil, err
		}
	}
	return cols, nil
}

//.........这里部分代码省略.........
		colDatumType = parser.TypeFloat
	case *parser.DecimalColType:
		col.Type.Kind = ColumnType_DECIMAL
		col.Type.Width = int32(t.Scale)
		col.Type.Precision = int32(t.Prec)
		colDatumType = parser.TypeDecimal
	case *parser.DateColType:
		col.Type.Kind = ColumnType_DATE
		colDatumType = parser.TypeDate
	case *parser.TimestampColType:
		col.Type.Kind = ColumnType_TIMESTAMP
		colDatumType = parser.TypeTimestamp
	case *parser.TimestampTZColType:
		col.Type.Kind = ColumnType_TIMESTAMPTZ
		colDatumType = parser.TypeTimestampTZ
	case *parser.IntervalColType:
		col.Type.Kind = ColumnType_INTERVAL
		colDatumType = parser.TypeInterval
	case *parser.StringColType:
		col.Type.Kind = ColumnType_STRING
		col.Type.Width = int32(t.N)
		colDatumType = parser.TypeString
	case *parser.BytesColType:
		col.Type.Kind = ColumnType_BYTES
		colDatumType = parser.TypeBytes
	case *parser.ArrayColType:
		if _, ok := t.ParamType.(*parser.IntColType); ok {
			col.Type.Kind = ColumnType_INT_ARRAY
		} else {
			return nil, nil, errors.Errorf("arrays of type %s are unsupported", t.ParamType)
		}
		colDatumType = parser.TypeIntArray
		for i, e := range t.BoundsExprs {
			ctx := parser.SemaContext{SearchPath: searchPath}
			te, err := parser.TypeCheckAndRequire(e, &ctx, parser.TypeInt, "array bounds")
			if err != nil {
				return nil, nil, errors.Wrapf(err, "couldn't get bound %d", i)
			}
			d, err := te.Eval(nil)
			if err != nil {
				return nil, nil, errors.Wrapf(err, "couldn't Eval bound %d", i)
			}
			b := d.(*parser.DInt)
			col.Type.ArrayDimensions = append(col.Type.ArrayDimensions, int32(*b))
		}
	default:
		return nil, nil, errors.Errorf("unexpected type %T", t)
	}

	if col.Type.Kind == ColumnType_DECIMAL {
		switch {
		case col.Type.Precision == 0 && col.Type.Width > 0:
			// TODO (seif): Find right range for error message.
			return nil, nil, errors.New("invalid NUMERIC precision 0")
		case col.Type.Precision < col.Type.Width:
			return nil, nil, fmt.Errorf("NUMERIC scale %d must be between 0 and precision %d",
				col.Type.Width, col.Type.Precision)
		}
	}

	if len(d.CheckExprs) > 0 {
		// Should never happen since `hoistConstraints` moves these to table level
		return nil, nil, errors.New("unexpected column CHECK constraint")
	}
	if d.HasFKConstraint() {
		// Should never happen since `hoistConstraints` moves these to table level
		return nil, nil, errors.New("unexpected column REFERENCED constraint")
	}

	if d.HasDefaultExpr() {
		// Verify the default expression type is compatible with the column type.
		if err := SanitizeVarFreeExpr(
			d.DefaultExpr.Expr, colDatumType, "DEFAULT", searchPath,
		); err != nil {
			return nil, nil, err
		}
		var p parser.Parser
		if err := p.AssertNoAggregationOrWindowing(
			d.DefaultExpr.Expr, "DEFAULT expressions", searchPath,
		); err != nil {
			return nil, nil, err
		}
		s := d.DefaultExpr.Expr.String()
		col.DefaultExpr = &s
	}

	var idx *IndexDescriptor
	if d.PrimaryKey || d.Unique {
		idx = &IndexDescriptor{
			Unique:           true,
			ColumnNames:      []string{string(d.Name)},
			ColumnDirections: []IndexDescriptor_Direction{IndexDescriptor_ASC},
		}
		if d.UniqueConstraintName != "" {
			idx.Name = string(d.UniqueConstraintName)
		}
	}

	return col, idx, nil
}

func (c *cliState) doCheckStatement(startState, contState, execState cliStateEnum) cliStateEnum {
	// From here on, client-side syntax checking is enabled.
	var parser parser.Parser
	parsedStmts, err := parser.Parse(c.concatLines, c.syntax)
	if err != nil {
		_ = c.invalidSyntax(0, "statement ignored: %v", err)

		// Even on failure, add the last (erroneous) lines as-is to the
		// history, so that the user can recall them later to fix them.
		for i := c.partialStmtsLen; i < len(c.partialLines); i++ {
			c.addHistory(c.partialLines[i])
		}

		// Stop here if exiterr is set.
		if c.errExit {
			return cliStop
		}

		// Otherwise, remove the erroneous lines from the buffered input,
		// then try again.
		c.partialLines = c.partialLines[:c.partialStmtsLen]
		if len(c.partialLines) == 0 {
			return startState
		}
		return contState
	}

	if !isInteractive {
		return execState
	}

	if c.normalizeHistory {
		// Add statements, not lines, to the history.
		for i := c.partialStmtsLen; i < len(parsedStmts); i++ {
			c.addHistory(parsedStmts[i].String() + ";")
		}
	} else {
		// Add the last lines received to the history.
		for i := c.partialStmtsLen; i < len(c.partialLines); i++ {
			c.addHistory(c.partialLines[i])
		}
	}

	// Replace the last entered lines by the last entered statements.
	c.partialLines = c.partialLines[:c.partialStmtsLen]
	for i := c.partialStmtsLen; i < len(parsedStmts); i++ {
		c.partialLines = append(c.partialLines, parsedStmts[i].String()+";")
	}

	nextState := execState

	// In interactive mode, we make some additional effort to help the user:
	// if the entry so far is starting an incomplete transaction, push
	// the user to enter input over multiple lines.
	if endsWithIncompleteTxn(parsedStmts) && c.lastInputLine != "" {
		if c.partialStmtsLen == 0 {
			fmt.Fprintln(osStderr, "Now adding input for a multi-line SQL transaction client-side.\n"+
				"Press Enter two times to send the SQL text collected so far to the server, or Ctrl+C to cancel.")
		}

		nextState = contState
	}

	c.partialStmtsLen = len(parsedStmts)

	return nextState
}