expression

package
v0.0.0-...-6dbff61 Latest Latest
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 Go to latest Published: May 24, 2017 License: Apache-2.0 Imports: 47 Imported by: 0

Documentation

Index

Constants

View Source 
const (
	SHA0   int = 0
	SHA224 int = 224
	SHA256 int = 256
	SHA384 int = 384
	SHA512 int = 512
)

Supported hash length of SHA-2 family

Variables

View Source 
var (
	// CurrentTimestamp is the keyword getting default value for datetime and timestamp type.
	CurrentTimestamp = "CURRENT_TIMESTAMP"

	// ZeroTimestamp shows the zero datetime and timestamp.
	ZeroTimestamp = "0000-00-00 00:00:00"
)
View Source 
var EvalAstExpr func(expr ast.ExprNode, ctx context.Context) (types.Datum, error)

EvalAstExpr evaluates ast expression directly.

View Source 
var MaxPropagateColsCnt = 100

MaxPropagateColsCnt means the max number of columns that can participate propagation.

View Source 
var Null = &Constant{
	Value:   types.NewDatum(nil),
	RetType: types.NewFieldType(mysql.TypeTiny),
}

Null stands for null constant.

View Source 
var One = &Constant{
	Value:   types.NewDatum(1),
	RetType: types.NewFieldType(mysql.TypeTiny),
}

One stands for a number 1.

View Source 
var Zero = &Constant{
	Value:   types.NewDatum(0),
	RetType: types.NewFieldType(mysql.TypeTiny),
}

Zero stands for a number 0.

Functions

func AggFuncToPBExpr 

func AggFuncToPBExpr(sc *variable.StatementContext, client kv.Client, aggFunc AggregationFunction) *tipb.Expr

AggFuncToPBExpr converts aggregate function to pb.

func EvalBool 

func EvalBool(exprList CNFExprs, row []types.Datum, ctx context.Context) (bool, error)

EvalBool evaluates expression list to a boolean value.

func ExpressionsToPB 

func ExpressionsToPB(sc *variable.StatementContext, exprs []Expression, client kv.Client) (pbExpr *tipb.Expr, pushed []Expression, remained []Expression)

ExpressionsToPB converts expression to tipb.Expr.

func ExpressionsToPBList 

func ExpressionsToPBList(sc *variable.StatementContext, exprs []Expression, client kv.Client) (pbExpr []*tipb.Expr)

ExpressionsToPBList converts expressions to tipb.Expr list for new plan.

func GetTimeValue 

func GetTimeValue(ctx context.Context, v interface{}, tp byte, fsp int) (types.Datum, error)

GetTimeValue gets the time value with type tp.

func GroupByItemToPB 

func GroupByItemToPB(sc *variable.StatementContext, client kv.Client, expr Expression) *tipb.ByItem

GroupByItemToPB converts group by items to pb.

func InferType 

func InferType(sc *variable.StatementContext, node ast.Node) error

InferType infers result type for ast.ExprNode.

func IsCurrentTimeExpr 

func IsCurrentTimeExpr(e ast.ExprNode) bool

IsCurrentTimeExpr returns whether e is CurrentTimeExpr.

func SortByItemToPB 

func SortByItemToPB(sc *variable.StatementContext, client kv.Client, expr Expression, desc bool) *tipb.ByItem

SortByItemToPB converts order by items to pb.

Types

type AggFunctionMode 

type AggFunctionMode int

AggFunctionMode stands for the aggregation function's mode. 

const (
	// CompleteMode function accepts origin data.
	CompleteMode AggFunctionMode = iota
	// FinalMode function accepts partial data.
	FinalMode
)

type AggregationFunction 

type AggregationFunction interface {
	fmt.Stringer
	json.Marshaler
	// Update during executing.
	Update(row []types.Datum, groupKey []byte, sc *variable.StatementContext) error

	// GetPartialResult will called by coprocessor to get partial results. For avg function, partial results will return
	// sum and count values at the same time.
	GetPartialResult(groupKey []byte) []types.Datum

	// StreamUpdate updates data using streaming algo.
	StreamUpdate(row []types.Datum, sc *variable.StatementContext) error

	// SetMode sets aggFunctionMode for aggregate function.
	SetMode(mode AggFunctionMode)

	// GetMode gets aggFunctionMode from aggregate function.
	GetMode() AggFunctionMode

	// GetGroupResult will be called when all data have been processed.
	GetGroupResult(groupKey []byte) types.Datum

	// GetStreamResult gets a result using streaming agg.
	GetStreamResult() types.Datum

	// GetArgs stands for getting all arguments.
	GetArgs() []Expression

	// GetName gets the aggregation function name.
	GetName() string

	// SetArgs sets argument by index.
	SetArgs(args []Expression)

	// Reset resets this aggregate function.
	Reset()

	// IsDistinct indicates if the aggregate function contains distinct attribute.
	IsDistinct() bool

	// SetContext sets the aggregate evaluation context.
	SetContext(ctx map[string](*aggEvaluateContext))

	// Equal checks whether two aggregation functions are equal.
	Equal(agg AggregationFunction, ctx context.Context) bool

	// Clone copies an aggregate function totally.
	Clone() AggregationFunction

	// GetType gets field type of aggregate function.
	GetType() *types.FieldType

	// CalculateDefaultValue gets the default value when the aggregate function's input is null.
	// The input stands for the schema of Aggregation's child. If the function can't produce a default value, the second
	// return value will be false.
	CalculateDefaultValue(schema *Schema, ctx context.Context) (types.Datum, bool)
}

AggregationFunction stands for aggregate functions.

func NewAggFunction 

func NewAggFunction(funcType string, funcArgs []Expression, distinct bool) AggregationFunction

NewAggFunction creates a new AggregationFunction.

func NewDistAggFunc 

func NewDistAggFunc(expr *tipb.Expr, fieldTps []*types.FieldType, sc *variable.StatementContext) (AggregationFunction, error)

NewDistAggFunc creates new Aggregate function for mock tikv.

type Assignment 

type Assignment struct {
	Col  *Column
	Expr Expression
}

Assignment represents a set assignment in Update, such as Update t set c1 = hex(12), c2 = c3 where c2 = 1

type BuiltinFunc 

type BuiltinFunc func([]types.Datum, context.Context) (types.Datum, error)

BuiltinFunc is the function signature for builtin functions

type CNFExprs 

type CNFExprs []Expression

CNFExprs stands for a CNF expression.

func (CNFExprs) Clone 

func (e CNFExprs) Clone() CNFExprs

Clone clones itself.

type Column 

type Column struct {
	FromID  string
	ColName model.CIStr
	DBName  model.CIStr
	TblName model.CIStr
	RetType *types.FieldType
	ID      int64
	// Position means the position of this column that appears in the select fields.
	// e.g. SELECT name as id , 1 - id as id , 1 + name as id, name as id from src having id = 1;
	// There are four ids in the same schema, so you can't identify the column through the FromID and ColName.
	Position int
	// IsAggOrSubq means if this column is referenced to a Aggregation column or a Subquery column.
	// If so, this column's name will be the plain sql text.
	IsAggOrSubq bool

	// Index is only used for execution.
	Index int
	// contains filtered or unexported fields
}

Column represents a column.

func ColumnInfos2Columns 

func ColumnInfos2Columns(tblName model.CIStr, colInfos []*model.ColumnInfo) []*Column

ColumnInfos2Columns converts a slice of ColumnInfo to a slice of Column.

func ExtractColumns 

func ExtractColumns(expr Expression) (cols []*Column)

ExtractColumns extracts all columns from an expression.

func (*Column) Clone 

func (col *Column) Clone() Expression

Clone implements Expression interface.

func (*Column) Decorrelate 

func (col *Column) Decorrelate(_ *Schema) Expression

Decorrelate implements Expression interface.

func (*Column) Equal 

func (col *Column) Equal(expr Expression, _ context.Context) bool

Equal implements Expression interface.

func (*Column) Eval 

func (col *Column) Eval(row []types.Datum) (types.Datum, error)

Eval implements Expression interface.

func (*Column) EvalDecimal 

func (col *Column) EvalDecimal(row []types.Datum, sc *variable.StatementContext) (*types.MyDecimal, bool, error)

EvalDecimal returns decimal representation of Column.

func (*Column) EvalDuration 

func (col *Column) EvalDuration(row []types.Datum, sc *variable.StatementContext) (types.Duration, bool, error)

EvalDuration returns Duration representation of Column.

func (*Column) EvalInt 

func (col *Column) EvalInt(row []types.Datum, sc *variable.StatementContext) (int64, bool, error)

EvalInt returns int representation of Column.

func (*Column) EvalReal 

func (col *Column) EvalReal(row []types.Datum, sc *variable.StatementContext) (float64, bool, error)

EvalReal returns real representation of Column.

func (*Column) EvalString 

func (col *Column) EvalString(row []types.Datum, sc *variable.StatementContext) (string, bool, error)

EvalString returns string representation of Column.

func (*Column) EvalTime 

func (col *Column) EvalTime(row []types.Datum, sc *variable.StatementContext) (types.Time, bool, error)

EvalTime returns DATE/DATETIME/TIMESTAMP representation of Column.

func (*Column) GetType 

func (col *Column) GetType() *types.FieldType

GetType implements Expression interface.

func (*Column) HashCode 

func (col *Column) HashCode() []byte

HashCode implements Expression interface.

func (*Column) IsCorrelated 

func (col *Column) IsCorrelated() bool

IsCorrelated implements Expression interface.

func (*Column) MarshalJSON 

func (col *Column) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler interface.

func (*Column) ResolveIndices 

func (col *Column) ResolveIndices(schema *Schema)

ResolveIndices implements Expression interface.

func (*Column) String 

func (col *Column) String() string

String implements Stringer interface.

type Constant 

type Constant struct {
	Value   types.Datum
	RetType *types.FieldType
}

Constant stands for a constant value.

func (*Constant) Clone 

func (c *Constant) Clone() Expression

Clone implements Expression interface.

func (*Constant) Decorrelate 

func (c *Constant) Decorrelate(_ *Schema) Expression

Decorrelate implements Expression interface.

func (*Constant) Equal 

func (c *Constant) Equal(b Expression, ctx context.Context) bool

Equal implements Expression interface.

func (*Constant) Eval 

func (c *Constant) Eval(_ []types.Datum) (types.Datum, error)

Eval implements Expression interface.

func (*Constant) EvalDecimal 

func (c *Constant) EvalDecimal(_ []types.Datum, sc *variable.StatementContext) (*types.MyDecimal, bool, error)

EvalDecimal returns decimal representation of Constant.

func (*Constant) EvalDuration 

func (c *Constant) EvalDuration(_ []types.Datum, sc *variable.StatementContext) (types.Duration, bool, error)

EvalDuration returns Duration representation of Constant.

func (*Constant) EvalInt 

func (c *Constant) EvalInt(_ []types.Datum, sc *variable.StatementContext) (int64, bool, error)

EvalInt returns int representation of Constant.

func (*Constant) EvalReal 

func (c *Constant) EvalReal(_ []types.Datum, sc *variable.StatementContext) (float64, bool, error)

EvalReal returns real representation of Constant.

func (*Constant) EvalString 

func (c *Constant) EvalString(_ []types.Datum, sc *variable.StatementContext) (string, bool, error)

EvalString returns string representation of Constant.

func (*Constant) EvalTime 

func (c *Constant) EvalTime(_ []types.Datum, sc *variable.StatementContext) (types.Time, bool, error)

EvalTime returns DATE/DATETIME/TIMESTAMP representation of Constant.

func (*Constant) GetType 

func (c *Constant) GetType() *types.FieldType

GetType implements Expression interface.

func (*Constant) HashCode 

func (c *Constant) HashCode() []byte

HashCode implements Expression interface.

func (*Constant) IsCorrelated 

func (c *Constant) IsCorrelated() bool

IsCorrelated implements Expression interface.

func (*Constant) MarshalJSON 

func (c *Constant) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler interface.

func (*Constant) ResolveIndices 

func (c *Constant) ResolveIndices(_ *Schema)

ResolveIndices implements Expression interface.

func (*Constant) String 

func (c *Constant) String() string

String implements fmt.Stringer interface.

type CorrelatedColumn 

type CorrelatedColumn struct {
	Column

	Data *types.Datum
}

CorrelatedColumn stands for a column in a correlated sub query.

func (*CorrelatedColumn) Clone 

func (col *CorrelatedColumn) Clone() Expression

Clone implements Expression interface.

func (*CorrelatedColumn) Decorrelate 

func (col *CorrelatedColumn) Decorrelate(schema *Schema) Expression

Decorrelate implements Expression interface.

func (*CorrelatedColumn) Equal 

func (col *CorrelatedColumn) Equal(expr Expression, ctx context.Context) bool

Equal implements Expression interface.

func (*CorrelatedColumn) Eval 

func (col *CorrelatedColumn) Eval(row []types.Datum) (types.Datum, error)

Eval implements Expression interface.

func (*CorrelatedColumn) EvalDecimal 

func (col *CorrelatedColumn) EvalDecimal(row []types.Datum, sc *variable.StatementContext) (*types.MyDecimal, bool, error)

EvalDecimal returns decimal representation of CorrelatedColumn.

func (*CorrelatedColumn) EvalDuration 

func (col *CorrelatedColumn) EvalDuration(row []types.Datum, sc *variable.StatementContext) (types.Duration, bool, error)

EvalDuration returns Duration representation of CorrelatedColumn.

func (*CorrelatedColumn) EvalInt 

func (col *CorrelatedColumn) EvalInt(row []types.Datum, sc *variable.StatementContext) (int64, bool, error)

EvalInt returns int representation of CorrelatedColumn.

func (*CorrelatedColumn) EvalReal 

func (col *CorrelatedColumn) EvalReal(row []types.Datum, sc *variable.StatementContext) (float64, bool, error)

EvalReal returns real representation of CorrelatedColumn.

func (*CorrelatedColumn) EvalString 

func (col *CorrelatedColumn) EvalString(row []types.Datum, sc *variable.StatementContext) (string, bool, error)

EvalString returns string representation of CorrelatedColumn.

func (*CorrelatedColumn) EvalTime 

func (col *CorrelatedColumn) EvalTime(row []types.Datum, sc *variable.StatementContext) (types.Time, bool, error)

EvalTime returns DATE/DATETIME/TIMESTAMP representation of CorrelatedColumn.

func (*CorrelatedColumn) IsCorrelated 

func (col *CorrelatedColumn) IsCorrelated() bool

IsCorrelated implements Expression interface.

func (*CorrelatedColumn) ResolveIndices 

func (col *CorrelatedColumn) ResolveIndices(_ *Schema)

ResolveIndices implements Expression interface.

type Expression 

type Expression interface {
	fmt.Stringer
	json.Marshaler

	// Eval evaluates an expression through a row.
	Eval(row []types.Datum) (types.Datum, error)

	// EvalInt returns the int64 representation of expression.
	EvalInt(row []types.Datum, sc *variable.StatementContext) (val int64, isNull bool, err error)

	// EvalReal returns the float64 representation of expression.
	EvalReal(row []types.Datum, sc *variable.StatementContext) (val float64, isNull bool, err error)

	// EvalString returns the string representation of expression.
	EvalString(row []types.Datum, sc *variable.StatementContext) (val string, isNull bool, err error)

	// EvalDecimal returns the decimal representation of expression.
	EvalDecimal(row []types.Datum, sc *variable.StatementContext) (val *types.MyDecimal, isNull bool, err error)

	// EvalTime returns the DATE/DATETIME/TIMESTAMP representation of expression.
	EvalTime(row []types.Datum, sc *variable.StatementContext) (val types.Time, isNull bool, err error)

	// EvalDuration returns the duration representation of expression.
	EvalDuration(row []types.Datum, sc *variable.StatementContext) (val types.Duration, isNull bool, err error)

	// GetType gets the type that the expression returns.
	GetType() *types.FieldType

	// Clone copies an expression totally.
	Clone() Expression

	// HashCode create the hashcode for expression
	HashCode() []byte

	// Equal checks whether two expressions are equal.
	Equal(e Expression, ctx context.Context) bool

	// IsCorrelated checks if this expression has correlated key.
	IsCorrelated() bool

	// Decorrelate try to decorrelate the expression by schema.
	Decorrelate(schema *Schema) Expression

	// ResolveIndices resolves indices by the given schema.
	ResolveIndices(schema *Schema)
}

Expression represents all scalar expression in SQL.

func Column2Exprs 

func Column2Exprs(cols []*Column) []Expression

Column2Exprs will transfer column slice to expression slice.

func ColumnSubstitute 

func ColumnSubstitute(expr Expression, schema *Schema, newExprs []Expression) Expression

ColumnSubstitute substitutes the columns in filter to expressions in select fields. e.g. select * from (select b as a from t) k where a < 10 => select * from (select b as a from t where b < 10) k.

func ComposeCNFCondition 

func ComposeCNFCondition(ctx context.Context, conditions ...Expression) Expression

ComposeCNFCondition composes CNF items into a balance deep CNF tree, which benefits a lot for pb decoder/encoder.

func ComposeDNFCondition 

func ComposeDNFCondition(ctx context.Context, conditions ...Expression) Expression

ComposeDNFCondition composes DNF items into a balance deep DNF tree.

func ConvertCol2CorCol 

func ConvertCol2CorCol(cond Expression, corCols []*CorrelatedColumn, outerSchema *Schema) Expression

ConvertCol2CorCol will convert the column in the condition which can be found in outerSchema to a correlated column whose Column is this column. And please make sure the outerSchema.Columns[i].Equal(corCols[i].Column)) holds when you call this.

func EvaluateExprWithNull 

func EvaluateExprWithNull(ctx context.Context, schema *Schema, expr Expression) (Expression, error)

EvaluateExprWithNull sets columns in schema as null and calculate the final result of the scalar function. If the Expression is a non-constant value, it means the result is unknown.

func FoldConstant 

func FoldConstant(expr Expression) Expression

FoldConstant does constant folding optimization on an expression.

func NewFunction 

func NewFunction(ctx context.Context, funcName string, retType *types.FieldType, args ...Expression) (Expression, error)

NewFunction creates a new scalar function or constant.

func PBToExpr 

func PBToExpr(expr *tipb.Expr, tps []*types.FieldType, sc *variable.StatementContext) (Expression, error)

PBToExpr converts pb structure to expression.

func PropagateConstant 

func PropagateConstant(ctx context.Context, conditions []Expression) []Expression

PropagateConstant propagate constant values of equality predicates and inequality predicates in a condition.

func PushDownNot 

func PushDownNot(expr Expression, not bool, ctx context.Context) Expression

PushDownNot pushes the `not` function down to the expression's arguments.

func ScalarFuncs2Exprs 

func ScalarFuncs2Exprs(funcs []*ScalarFunction) []Expression

ScalarFuncs2Exprs converts []*ScalarFunction to []Expression.

func SplitCNFItems 

func SplitCNFItems(onExpr Expression) []Expression

SplitCNFItems splits CNF items. CNF means conjunctive normal form, e.g. "a and b and c".

func SplitDNFItems 

func SplitDNFItems(onExpr Expression) []Expression

SplitDNFItems splits DNF items. DNF means disjunctive normal form, e.g. "a or b or c".

func SubstituteCorCol2Constant 

func SubstituteCorCol2Constant(expr Expression) (Expression, error)

SubstituteCorCol2Constant will substitute correlated column to constant value which it contains. If the args of one scalar function are all constant, we will substitute it to constant.

type KeyInfo 

type KeyInfo []*Column

KeyInfo stores the columns of one unique key or primary key.

func (KeyInfo) Clone 

func (ki KeyInfo) Clone() KeyInfo

Clone copies the entire UniqueKey.

type ScalarFunction 

type ScalarFunction struct {
	FuncName model.CIStr
	// RetType is the type that ScalarFunction returns.
	// TODO: Implement type inference here, now we use ast's return type temporarily.
	RetType  *types.FieldType
	Function builtinFunc
}

ScalarFunction is the function that returns a value.

func NewCastFunc 

func NewCastFunc(tp *types.FieldType, arg Expression, ctx context.Context) *ScalarFunction

NewCastFunc creates a new cast function.

func NewValuesFunc 

func NewValuesFunc(offset int, retTp *types.FieldType, ctx context.Context) *ScalarFunction

NewValuesFunc creates a new values function.

func (*ScalarFunction) Clone 

func (sf *ScalarFunction) Clone() Expression

Clone implements Expression interface.

func (*ScalarFunction) Decorrelate 

func (sf *ScalarFunction) Decorrelate(schema *Schema) Expression

Decorrelate implements Expression interface.

func (*ScalarFunction) Equal 

func (sf *ScalarFunction) Equal(e Expression, ctx context.Context) bool

Equal implements Expression interface.

func (*ScalarFunction) Eval 

func (sf *ScalarFunction) Eval(row []types.Datum) (types.Datum, error)

Eval implements Expression interface.

func (*ScalarFunction) EvalDecimal 

func (sf *ScalarFunction) EvalDecimal(row []types.Datum, sc *variable.StatementContext) (*types.MyDecimal, bool, error)

EvalDecimal implements Expression interface.

func (*ScalarFunction) EvalDuration 

func (sf *ScalarFunction) EvalDuration(row []types.Datum, sc *variable.StatementContext) (types.Duration, bool, error)

EvalDuration implements Expression interface.

func (*ScalarFunction) EvalInt 

func (sf *ScalarFunction) EvalInt(row []types.Datum, sc *variable.StatementContext) (int64, bool, error)

EvalInt implements Expression interface.

func (*ScalarFunction) EvalReal 

func (sf *ScalarFunction) EvalReal(row []types.Datum, sc *variable.StatementContext) (float64, bool, error)

EvalReal implements Expression interface.

func (*ScalarFunction) EvalString 

func (sf *ScalarFunction) EvalString(row []types.Datum, sc *variable.StatementContext) (string, bool, error)

EvalString implements Expression interface.

func (*ScalarFunction) EvalTime 

func (sf *ScalarFunction) EvalTime(row []types.Datum, sc *variable.StatementContext) (types.Time, bool, error)

EvalTime implements Expression interface.

func (*ScalarFunction) GetArgs 

func (sf *ScalarFunction) GetArgs() []Expression

GetArgs gets arguments of function.

func (*ScalarFunction) GetCtx 

func (sf *ScalarFunction) GetCtx() context.Context

GetCtx gets the context of function.

func (*ScalarFunction) GetType 

func (sf *ScalarFunction) GetType() *types.FieldType

GetType implements Expression interface.

func (*ScalarFunction) HashCode 

func (sf *ScalarFunction) HashCode() []byte

HashCode implements Expression interface.

func (*ScalarFunction) IsCorrelated 

func (sf *ScalarFunction) IsCorrelated() bool

IsCorrelated implements Expression interface.

func (*ScalarFunction) MarshalJSON 

func (sf *ScalarFunction) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler interface.

func (*ScalarFunction) ResolveIndices 

func (sf *ScalarFunction) ResolveIndices(schema *Schema)

ResolveIndices implements Expression interface.

func (*ScalarFunction) String 

func (sf *ScalarFunction) String() string

String implements fmt.Stringer interface.

type Schema 

type Schema struct {
	Columns   []*Column
	Keys      []KeyInfo
	MaxOneRow bool
}

Schema stands for the row schema and unique key information get from input.

func MergeSchema 

func MergeSchema(lSchema, rSchema *Schema) *Schema

MergeSchema will merge two schema into one schema.

func NewSchema 

func NewSchema(cols ...*Column) *Schema

NewSchema returns a schema made by its parameter.

func TableInfo2Schema 

func TableInfo2Schema(tbl *model.TableInfo) *Schema

TableInfo2Schema converts table info to schema.

func (*Schema) Append 

func (s *Schema) Append(col ...*Column)

Append append new column to the columns stored in schema.

func (*Schema) Clone 

func (s *Schema) Clone() *Schema

Clone copies the total schema.

func (*Schema) ColumnIndex 

func (s *Schema) ColumnIndex(col *Column) int

ColumnIndex finds the index for a column.

func (*Schema) ColumnsIndices 

func (s *Schema) ColumnsIndices(cols []*Column) (ret []int)

ColumnsIndices will return a slice which contains the position of each column in schema. If there is one column that doesn't match, nil will be returned.

func (*Schema) Contains 

func (s *Schema) Contains(col *Column) bool

Contains checks if the schema contains the column.

func (*Schema) FindColumn 

func (s *Schema) FindColumn(astCol *ast.ColumnName) (*Column, error)

FindColumn finds an Column from schema for a ast.ColumnName. It compares the db/table/column names. If there are more than one result, it will raise ambiguous error.

func (*Schema) IsUniqueKey 

func (s *Schema) IsUniqueKey(col *Column) bool

IsUniqueKey checks if this column is a unique key.

func (*Schema) Len 

func (s *Schema) Len() int

Len returns the number of columns in schema.

func (*Schema) RetrieveColumn 

func (s *Schema) RetrieveColumn(col *Column) *Column

RetrieveColumn retrieves column in expression from the columns in schema.

func (*Schema) SetUniqueKeys 

func (s *Schema) SetUniqueKeys(keys []KeyInfo)

SetUniqueKeys will set the value of Schema.Keys.

func (*Schema) String 

func (s *Schema) String() string

String implements fmt.Stringer interface.

type VarAssignment 

type VarAssignment struct {
	Name        string
	Expr        Expression
	IsDefault   bool
	IsGlobal    bool
	IsSystem    bool
	ExtendValue *Constant
}

VarAssignment represents a variable assignment in Set, such as set global a = 1.

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