expression

package
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 Go to latest Published: Nov 24, 2016 License: Apache-2.0 Imports: 15 Imported by: 0

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Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func EvalBool 

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

EvalBool evaluates expression to a boolean value.

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, ctx context.Context) error

	// StreamUpdate updates data using streaming algo.
	StreamUpdate(row []types.Datum, ctx context.Context) 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)

	// Clear collects the mapper's memory.
	Clear()

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

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

	// Equal checks whether two aggregation functions are equal.
	Equal(agg AggregationFunction) 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) (types.Datum, bool)
}

AggregationFunction stands for aggregate functions.

func NewAggFunction 

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

NewAggFunction creates a new AggregationFunction.

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 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

	// Only used for execution.
	Index int
}

Column represents a column.

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) bool

Equal implements Expression interface.

func (*Column) Eval 

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

Eval implements Expression interface.

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) bool

Equal implements Expression interface.

func (*Constant) Eval 

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

Eval implements Expression interface.

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) bool

Equal implements Expression interface.

func (*CorrelatedColumn) Eval 

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

Eval implements Expression interface.

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, ctx context.Context) (types.Datum, error)

	// Get the expression return type.
	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) 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 ComposeCNFCondition 

func ComposeCNFCondition(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(conditions []Expression) Expression

ComposeDNFCondition composes DNF items into a balance deep DNF tree.

func EvaluateExprWithNull 

func EvaluateExprWithNull(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 NewFunction 

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

NewFunction creates a new scalar function or constant.

func ScalarFuncs2Exprs 

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

ScalarFuncs2Exprs converts []*ScalarFunction to []Expression.

func Schema2Exprs 

func Schema2Exprs(schema Schema) []Expression

Schema2Exprs converts []*Column 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".

type ScalarFunction 

type ScalarFunction struct {
	Args     []Expression
	FuncName model.CIStr
	// TODO: Implement type inference here, now we use ast's return type temporarily.
	RetType   *types.FieldType
	Function  evaluator.BuiltinFunc
	ArgValues []types.Datum
}

ScalarFunction is the function that returns a value.

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) bool

Equal implements Expression interface.

func (*ScalarFunction) Eval 

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

Eval implements Expression interface.

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 []*Column

Schema stands for the row schema get from input.

func ResultFieldsToSchema 

func ResultFieldsToSchema(fields []*ast.ResultField) Schema

ResultFieldsToSchema converts slice of result fields to schema.

func (Schema) Clone 

func (s Schema) Clone() Schema

Clone copies the total schema.

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) GetIndex 

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

GetIndex finds the index for a column.

func (Schema) InitIndices 

func (s Schema) InitIndices()

InitIndices sets indices for 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) String 

func (s Schema) String() string

String implements fmt.Stringer interface.

Source Files

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