aggregation

Documentation

Index

• type AggFuncDesc
  • func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expression, ...) (*AggFuncDesc, error)
  • func (a *AggFuncDesc) Clone() *AggFuncDesc
  • func (a *AggFuncDesc) Equal(ctx sessionctx.Context, other *AggFuncDesc) bool
  • func (a *AggFuncDesc) EvalNullValueInOuterJoin(ctx sessionctx.Context, schema *expression.Schema) (types.Datum, bool)
  • func (a *AggFuncDesc) Split(ordinal []int) (partialAggDesc, finalAggDesc *AggFuncDesc)
  • func (a *AggFuncDesc) String() string
  • func (a *AggFuncDesc) UpdateNotNullFlag4RetType(hasGroupBy, allAggsFirstRow bool) error
  • func (a *AggFuncDesc) WrapCastAsDecimalForAggArgs(ctx sessionctx.Context)
  • func (a *AggFuncDesc) WrapCastForAggArgs(ctx sessionctx.Context)
• type AggFunctionMode

Types

type AggFuncDesc

type AggFuncDesc struct {

	// Mode represents the execution mode of the aggregation function.
	Mode AggFunctionMode
	// HasDistinct represents whether the aggregation function contains distinct attribute.
	HasDistinct bool
	// OrderByItems represents the order by clause used in GROUP_CONCAT
	OrderByItems []*util.ByItems
	// contains filtered or unexported fields
}

AggFuncDesc describes an aggregation function signature, only used in planner.

func NewAggFuncDesc

func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expression, hasDistinct bool) (*AggFuncDesc, error)

NewAggFuncDesc creates an aggregation function signature descriptor.

func (*AggFuncDesc) Clone

func (a *AggFuncDesc) Clone() *AggFuncDesc

Clone copies an aggregation function signature totally.

func (*AggFuncDesc) Equal

func (a *AggFuncDesc) Equal(ctx sessionctx.Context, other *AggFuncDesc) bool

Equal checks whether two aggregation function signatures are equal.

func (*AggFuncDesc) EvalNullValueInOuterJoin

func (a *AggFuncDesc) EvalNullValueInOuterJoin(ctx sessionctx.Context, schema *expression.Schema) (types.Datum, bool)

EvalNullValueInOuterJoin gets the null value when the aggregation is upon an outer join, and the aggregation function's input is null. If there is no matching row for the inner table of an outer join, an aggregation function only involves constant and/or columns belongs to the inner table will be set to the null value. The input stands for the schema of Aggregation's child. If the function can't produce a null value, the second return value will be false. e.g. Table t with only one row: +-------+---------+---------+ | Table | Field | Type | +-------+---------+---------+ | t | a | int(11) | +-------+---------+---------+ +------+ | a | +------+ | 1 | +------+

Table s which is empty: +-------+---------+---------+ | Table | Field | Type | +-------+---------+---------+ | s | a | int(11) | +-------+---------+---------+

Query: `select t.a as `t.a`, count(95), sum(95), avg(95), bit_or(95), bit_and(95), bit_or(95), max(95), min(95), s.a as `s.a`, avg(95) from t left join s on t.a = s.a;` +------+-----------+---------+---------+------------+-------------+------------+---------+---------+------+----------+ | t.a | count(95) | sum(95) | avg(95) | bit_or(95) | bit_and(95) | bit_or(95) | max(95) | min(95) | s.a | avg(s.a) | +------+-----------+---------+---------+------------+-------------+------------+---------+---------+------+----------+ | 1 | 1 | 95 | 95.0000 | 95 | 95 | 95 | 95 | 95 | NULL | NULL | +------+-----------+---------+---------+------------+-------------+------------+---------+---------+------+----------+

func (*AggFuncDesc) Split

func (a *AggFuncDesc) Split(ordinal []int) (partialAggDesc, finalAggDesc *AggFuncDesc)

Split splits `a` into two aggregate descriptors for partial phase and final phase individually. This function is only used when executing aggregate function parallelly. ordinal indicates the column ordinal of the intermediate result.

func (*AggFuncDesc) String

func (a *AggFuncDesc) String() string

String implements the fmt.Stringer interface.

func (*AggFuncDesc) UpdateNotNullFlag4RetType

func (a *AggFuncDesc) UpdateNotNullFlag4RetType(hasGroupBy, allAggsFirstRow bool) error

UpdateNotNullFlag4RetType checks if we should remove the NotNull flag for the return type of the agg.

func (*AggFuncDesc) WrapCastAsDecimalForAggArgs

func (a *AggFuncDesc) WrapCastAsDecimalForAggArgs(ctx sessionctx.Context)

WrapCastAsDecimalForAggArgs wraps the args of some specific aggregate functions with a cast as decimal function. See issue #19426

func (*AggFuncDesc) WrapCastForAggArgs

func (a *AggFuncDesc) WrapCastForAggArgs(ctx sessionctx.Context)

WrapCastForAggArgs wraps the args of an aggregate function with a cast function.

type AggFunctionMode

type AggFunctionMode int

AggFunctionMode stands for the aggregation function's mode.

const (
	CompleteMode AggFunctionMode = iota
	FinalMode
	Partial1Mode
	Partial2Mode
)

|-----------------|--------------|--------------| | AggFunctionMode | input | output | |-----------------|--------------|--------------| | CompleteMode | origin data | final result | | FinalMode | partial data | final result | | Partial1Mode | origin data | partial data | | Partial2Mode | partial data | partial data | | DedupMode | origin data | origin data | |-----------------|--------------|--------------|