statistics

package
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 Go to latest Published: Jul 11, 2021 License: Apache-2.0 Imports: 38 Imported by: 0

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Index

Constants

View Source 
const (
	CurStatsVersion = Version1
	Version1        = 1
)

constants for stats version. These const can be used for solving compatibility issue.

View Source 
const (
	IndexType = iota
	PkType
	ColType
)

The type of the StatsNode.

View Source 
const AnalyzeFlag = 1

AnalyzeFlag is set when the statistics comes from analyze and has not been modified by feedback.

View Source 
const MaxErrorRate = 0.25

MaxErrorRate is the max error rate of estimate row count of a not pseudo column. If the table is pseudo, but the average error rate is less than MaxErrorRate, then the column is not pseudo.

View Source 
const PseudoVersion uint64 = 0

PseudoVersion means the pseudo statistics version is 0.

Variables

View Source 
var (
	// MaxNumberOfRanges is the max number of ranges before split to collect feedback.
	MaxNumberOfRanges = 20
	// FeedbackProbability is the probability to collect the feedback.
	FeedbackProbability = atomic.NewFloat64(0)
)
View Source 
var HistogramNeededColumns = neededColumnMap{/* contains filtered or unexported fields */}

HistogramNeededColumns stores the columns whose Histograms need to be loaded from physical kv layer. Currently, we only load index/pk's Histogram from kv automatically. Columns' are loaded by needs.

View Source 
var RatioOfPseudoEstimate = atomic.NewFloat64(0.7)

RatioOfPseudoEstimate means if modifyCount / statsTblCount is greater than this ratio, we think the stats is invalid and use pseudo estimation.

Functions

func AddNewAnalyzeJob 

func AddNewAnalyzeJob(job *AnalyzeJob)

AddNewAnalyzeJob adds new analyze job.

func CMSketchToProto 

func CMSketchToProto(c *CMSketch) *tipb.CMSketch

CMSketchToProto converts CMSketch to its protobuf representation.

func ClearHistoryJobs 

func ClearHistoryJobs()

ClearHistoryJobs clears all history jobs.

func ConvertDatumsType 

func ConvertDatumsType(vals []types.Datum, ft *types.FieldType, loc *time.Location) error

ConvertDatumsType converts the datums type to `ft`.

func DecodeFeedback 

func DecodeFeedback(val []byte, q *QueryFeedback, c *CMSketch, ft *types.FieldType) error

DecodeFeedback decodes a byte slice to feedback.

func EncodeCMSketchWithoutTopN 

func EncodeCMSketchWithoutTopN(c *CMSketch) ([]byte, error)

EncodeCMSketchWithoutTopN encodes the given CMSketch to byte slice. Note that it does not include the topN.

func EncodeFeedback 

func EncodeFeedback(q *QueryFeedback) ([]byte, error)

EncodeFeedback encodes the given feedback to byte slice.

func FMSketchToProto 

func FMSketchToProto(s *FMSketch) *tipb.FMSketch

FMSketchToProto converts FMSketch to its protobuf representation.

func GetMaxValue 

func GetMaxValue(ft *types.FieldType) (max types.Datum)

GetMaxValue returns the max value datum for each type.

func GetMinValue 

func GetMinValue(ft *types.FieldType) (min types.Datum)

GetMinValue returns the min value datum for each type.

func GetOrdinalOfRangeCond 

func GetOrdinalOfRangeCond(sc *stmtctx.StatementContext, ran *ranger.Range) int

GetOrdinalOfRangeCond gets the ordinal of the position range condition, if not exist, it returns the end position.

func GetPseudoRowCountByColumnRanges 

func GetPseudoRowCountByColumnRanges(sc *stmtctx.StatementContext, tableRowCount float64, columnRanges []*ranger.Range, colIdx int) (float64, error)

GetPseudoRowCountByColumnRanges calculate the row count by the ranges if there's no statistics information for this column.

func HistogramEqual 

func HistogramEqual(a, b *Histogram, ignoreID bool) bool

HistogramEqual tests if two histograms are equal.

func HistogramToProto 

func HistogramToProto(hg *Histogram) *tipb.Histogram

HistogramToProto converts Histogram to its protobuf representation. Note that when this is used, the lower/upper bound in the bucket must be BytesDatum.

func IsAnalyzed 

func IsAnalyzed(flag int64) bool

IsAnalyzed checks whether this flag contains AnalyzeFlag.

func MoveToHistory 

func MoveToHistory(job *AnalyzeJob)

MoveToHistory moves the analyze job to history.

func ResetAnalyzeFlag 

func ResetAnalyzeFlag(flag int64) int64

ResetAnalyzeFlag resets the AnalyzeFlag because it has been modified by feedback.

func RowToDatums 

func RowToDatums(row chunk.Row, fields []*ast.ResultField) []types.Datum

RowToDatums converts row to datum slice.

func SampleCollectorToProto 

func SampleCollectorToProto(c *SampleCollector) *tipb.SampleCollector

SampleCollectorToProto converts SampleCollector to its protobuf representation.

func SortSampleItems 

func SortSampleItems(sc *stmtctx.StatementContext, items []*SampleItem) error

SortSampleItems sorts a slice of SampleItem.

func SplitFeedbackByQueryType 

func SplitFeedbackByQueryType(feedbacks []Feedback) ([]Feedback, []Feedback)

SplitFeedbackByQueryType splits the feedbacks into equality feedbacks and range feedbacks.

func SupportColumnType 

func SupportColumnType(ft *types.FieldType) bool

SupportColumnType checks if the type of the column can be updated by feedback.

func ValueToString 

func ValueToString(value *types.Datum, idxCols int) (string, error)

ValueToString converts a possible encoded value to a formatted string. If the value is encoded, then idxCols equals to number of origin values, else idxCols is 0.

Types

type AnalyzeJob 

type AnalyzeJob struct {
	sync.Mutex
	DBName        string
	TableName     string
	PartitionName string
	JobInfo       string
	RowCount      int64
	StartTime     time.Time
	State         string
	// contains filtered or unexported fields
}

AnalyzeJob is used to represent the status of one analyze job.

func GetAllAnalyzeJobs 

func GetAllAnalyzeJobs() []*AnalyzeJob

GetAllAnalyzeJobs gets all analyze jobs.

func (*AnalyzeJob) Finish 

func (job *AnalyzeJob) Finish(meetError bool)

Finish update the status of analyze job to finished or failed according to `meetError`.

func (*AnalyzeJob) Start 

func (job *AnalyzeJob) Start()

Start marks status of the analyze job as running and update the start time.

func (*AnalyzeJob) Update 

func (job *AnalyzeJob) Update(rowCount int64)

Update updates the row count of analyze job.

type Bucket 

type Bucket struct {
	Count  int64
	Repeat int64
}

Bucket store the bucket count and repeat.

type BucketFeedback 

type BucketFeedback struct {
	// contains filtered or unexported fields
}

BucketFeedback stands for all the feedback for a bucket.

type CMSketch 

type CMSketch struct {
	// contains filtered or unexported fields
}

CMSketch is used to estimate point queries. Refer: https://en.wikipedia.org/wiki/Count-min_sketch

func CMSketchFromProto 

func CMSketchFromProto(protoSketch *tipb.CMSketch) *CMSketch

CMSketchFromProto converts CMSketch from its protobuf representation.

func LoadCMSketchWithTopN 

func LoadCMSketchWithTopN(exec sqlexec.RestrictedSQLExecutor, tableID, isIndex, histID int64, cms []byte) (*CMSketch, error)

LoadCMSketchWithTopN loads the CM sketch with topN from storage.

func NewCMSketch 

func NewCMSketch(d, w int32) *CMSketch

NewCMSketch returns a new CM sketch.

func NewCMSketchWithTopN 

func NewCMSketchWithTopN(d, w int32, sample [][]byte, numTop uint32, rowCount uint64) (*CMSketch, uint64, uint64)

NewCMSketchWithTopN returns a new CM sketch with TopN elements, the estimate NDV and the scale ratio.

func UpdateCMSketch 

func UpdateCMSketch(c *CMSketch, eqFeedbacks []Feedback) *CMSketch

UpdateCMSketch updates the CMSketch by feedback.

func (*CMSketch) Copy 

func (c *CMSketch) Copy() *CMSketch

Copy makes a copy for current CMSketch.

func (*CMSketch) Equal 

func (c *CMSketch) Equal(rc *CMSketch) bool

Equal tests if two CM Sketch equal, it is only used for test.

func (*CMSketch) GetWidthAndDepth 

func (c *CMSketch) GetWidthAndDepth() (int32, int32)

GetWidthAndDepth returns the width and depth of CM Sketch.

func (*CMSketch) InsertBytes 

func (c *CMSketch) InsertBytes(bytes []byte)

InsertBytes inserts the bytes value into the CM Sketch.

func (*CMSketch) MergeCMSketch 

func (c *CMSketch) MergeCMSketch(rc *CMSketch, numTopN uint32) error

MergeCMSketch merges two CM Sketch.

func (*CMSketch) MergeCMSketch4IncrementalAnalyze 

func (c *CMSketch) MergeCMSketch4IncrementalAnalyze(rc *CMSketch) error

MergeCMSketch4IncrementalAnalyze merges two CM Sketch for incremental analyze. Since there is no value that appears partially in `c` and `rc` for incremental analyze, it uses `max` to merge them. Here is a simple proof: when we query from the CM sketch, we use the `min` to get the answer: 

(1): For values that only appears in `c, using `max` to merge them affects the `min` query result less than using `sum`;
(2): For values that only appears in `rc`, it is the same as condition (1);
(3): For values that appears both in `c` and `rc`, if they do not appear partially in `c` and `rc`, for example,
     if `v` appears 5 times in the table, it can appears 5 times in `c` and 3 times in `rc`, then `max` also gives the correct answer.

So in fact, if we can know the number of appearances of each value in the first place, it is better to use `max` to construct the CM sketch rather than `sum`.

func (*CMSketch) QueryBytes 

func (c *CMSketch) QueryBytes(d []byte) uint64

QueryBytes is used to query the count of specified bytes.

func (*CMSketch) TopN 

func (c *CMSketch) TopN() []*TopNMeta

TopN gets all the topN meta.

func (*CMSketch) TotalCount 

func (c *CMSketch) TotalCount() uint64

TotalCount returns the count, it is only used for test.

type Column 

type Column struct {
	Histogram
	*CMSketch
	PhysicalID int64
	Count      int64
	Info       *model.ColumnInfo
	IsHandle   bool
	ErrorRate
	Flag           int64
	LastAnalyzePos types.Datum
}

Column represents a column histogram.

func (*Column) AvgColSize 

func (c *Column) AvgColSize(count int64) float64

AvgColSize is the average column size of the histogram.

func (*Column) GetColumnRowCount 

func (c *Column) GetColumnRowCount(sc *stmtctx.StatementContext, ranges []*ranger.Range, modifyCount int64) (float64, error)

GetColumnRowCount estimates the row count by a slice of Range.

func (*Column) IsInvalid 

func (c *Column) IsInvalid(sc *stmtctx.StatementContext, collPseudo bool) bool

IsInvalid checks if this column is invalid. If this column has histogram but not loaded yet, then we mark it as need histogram.

func (*Column) String 

func (c *Column) String() string

type ErrorRate 

type ErrorRate struct {
	ErrorTotal float64
	QueryTotal int64
}

ErrorRate is the error rate of estimate row count by bucket and cm sketch.

func (*ErrorRate) Merge 

func (e *ErrorRate) Merge(rate *ErrorRate)

Merge range merges two ErrorRate.

func (*ErrorRate) NotAccurate 

func (e *ErrorRate) NotAccurate() bool

NotAccurate is true when the total of query is zero or the average error rate is greater than MaxErrorRate.

func (*ErrorRate) Update 

func (e *ErrorRate) Update(rate float64)

Update updates the ErrorRate.

type FMSketch 

type FMSketch struct {
	// contains filtered or unexported fields
}

FMSketch is used to count the number of distinct elements in a set.

func FMSketchFromProto 

func FMSketchFromProto(protoSketch *tipb.FMSketch) *FMSketch

FMSketchFromProto converts FMSketch from its protobuf representation.

func NewFMSketch 

func NewFMSketch(maxSize int) *FMSketch

NewFMSketch returns a new FM sketch.

func (*FMSketch) InsertValue 

func (s *FMSketch) InsertValue(sc *stmtctx.StatementContext, value types.Datum) error

InsertValue inserts a value into the FM sketch.

func (*FMSketch) NDV 

func (s *FMSketch) NDV() int64

NDV returns the ndv of the sketch.

type Feedback 

type Feedback struct {
	Lower  *types.Datum
	Upper  *types.Datum
	Count  int64
	Repeat int64
}

Feedback represents the total scan count in range [lower, upper).

type HistColl 

type HistColl struct {
	PhysicalID int64
	// HavePhysicalID is true means this HistColl is from single table and have its ID's information.
	// The physical id is used when try to load column stats from storage.
	HavePhysicalID bool
	Columns        map[int64]*Column
	Indices        map[int64]*Index
	// Idx2ColumnIDs maps the index id to its column ids. It's used to calculate the selectivity in planner.
	Idx2ColumnIDs map[int64][]int64
	// ColID2IdxID maps the column id to index id whose first column is it. It's used to calculate the selectivity in planner.
	ColID2IdxID map[int64]int64
	Pseudo      bool
	Count       int64
	ModifyCount int64 // Total modify count in a table.
}

HistColl is a collection of histogram. It collects enough information for plan to calculate the selectivity.

func (*HistColl) GenerateHistCollFromColumnInfo 

func (coll *HistColl) GenerateHistCollFromColumnInfo(infos []*model.ColumnInfo, columns []*expression.Column) *HistColl

GenerateHistCollFromColumnInfo generates a new HistColl whose ColID2IdxID and IdxID2ColIDs is built from the given parameter.

func (*HistColl) GetRowCountByColumnRanges 

func (coll *HistColl) GetRowCountByColumnRanges(sc *stmtctx.StatementContext, colID int64, colRanges []*ranger.Range) (float64, error)

GetRowCountByColumnRanges estimates the row count by a slice of Range.

func (*HistColl) GetRowCountByIndexRanges 

func (coll *HistColl) GetRowCountByIndexRanges(sc *stmtctx.StatementContext, idxID int64, indexRanges []*ranger.Range) (float64, error)

GetRowCountByIndexRanges estimates the row count by a slice of Range.

func (*HistColl) GetRowCountByIntColumnRanges 

func (coll *HistColl) GetRowCountByIntColumnRanges(sc *stmtctx.StatementContext, colID int64, intRanges []*ranger.Range) (float64, error)

GetRowCountByIntColumnRanges estimates the row count by a slice of IntColumnRange.

func (*HistColl) NewHistCollBySelectivity 

func (coll *HistColl) NewHistCollBySelectivity(sc *stmtctx.StatementContext, statsNodes []*StatsNode) *HistColl

NewHistCollBySelectivity creates new HistColl by the given statsNodes.

func (*HistColl) Selectivity 

func (coll *HistColl) Selectivity(ctx sessionctx.Context, exprs []expression.Expression) (float64, []*StatsNode, error)

Selectivity is a function calculate the selectivity of the expressions. The definition of selectivity is (row count after filter / row count before filter). And exprs must be CNF now, in other words, `exprs[0] and exprs[1] and ... and exprs[len - 1]` should be held when you call this. Currently the time complexity is o(n^2).

type Histogram 

type Histogram struct {
	ID        int64 // Column ID.
	NDV       int64 // Number of distinct values.
	NullCount int64 // Number of null values.
	// LastUpdateVersion is the version that this histogram updated last time.
	LastUpdateVersion uint64

	Tp *types.FieldType

	// Histogram elements.
	//
	// A bucket bound is the smallest and greatest values stored in the bucket. The lower and upper bound
	// are stored in one column.
	//
	// A bucket count is the number of items stored in all previous buckets and the current bucket.
	// Bucket counts are always in increasing order.
	//
	// A bucket repeat is the number of repeats of the bucket value, it can be used to find popular values.
	Bounds  *chunk.Chunk
	Buckets []Bucket

	// TotColSize is the total column size for the histogram.
	TotColSize int64

	// Correlation is the statistical correlation between physical row ordering and logical ordering of
	// the column values. This ranges from -1 to +1, and it is only valid for Column histogram, not for
	// Index histogram.
	Correlation float64
	// contains filtered or unexported fields
}

Histogram represents statistics for a column or index.

func BuildColumn 

func BuildColumn(ctx sessionctx.Context, numBuckets, id int64, collector *SampleCollector, tp *types.FieldType) (*Histogram, error)

BuildColumn builds histogram from samples for column.

func BuildColumnHist 

func BuildColumnHist(ctx sessionctx.Context, numBuckets, id int64, collector *SampleCollector, tp *types.FieldType, count int64, ndv int64, nullCount int64) (*Histogram, error)

BuildColumnHist build a histogram for a column. numBuckets: number of buckets for the histogram. id: the id of the table. collector: the collector of samples. tp: the FieldType for the column. count: represents the row count for the column. ndv: represents the number of distinct values for the column. nullCount: represents the number of null values for the column.

func HistogramFromProto 

func HistogramFromProto(protoHg *tipb.Histogram) *Histogram

HistogramFromProto converts Histogram from its protobuf representation. Note that we will set BytesDatum for the lower/upper bound in the bucket, the decode will be after all histograms merged.

func MergeHistograms 

func MergeHistograms(sc *stmtctx.StatementContext, lh *Histogram, rh *Histogram, bucketSize int) (*Histogram, error)

MergeHistograms merges two histograms.

func NewHistogram 

func NewHistogram(id, ndv, nullCount int64, version uint64, tp *types.FieldType, bucketSize int, totColSize int64) *Histogram

NewHistogram creates a new histogram.

func UpdateHistogram 

func UpdateHistogram(h *Histogram, feedback *QueryFeedback) *Histogram

UpdateHistogram updates the histogram according buckets.

func (*Histogram) AppendBucket 

func (hg *Histogram) AppendBucket(lower *types.Datum, upper *types.Datum, count, repeat int64)

AppendBucket appends a bucket into `hg`.

func (*Histogram) AvgCountPerNotNullValue 

func (hg *Histogram) AvgCountPerNotNullValue(totalCount int64) float64

AvgCountPerNotNullValue gets the average row count per value by the data of histogram.

func (*Histogram) BetweenRowCount 

func (hg *Histogram) BetweenRowCount(a, b types.Datum) float64

BetweenRowCount estimates the row count where column greater or equal to a and less than b.

func (*Histogram) BucketToString 

func (hg *Histogram) BucketToString(bktID, idxCols int) string

BucketToString change the given bucket to string format.

func (*Histogram) ConvertTo 

func (hg *Histogram) ConvertTo(sc *stmtctx.StatementContext, tp *types.FieldType) (*Histogram, error)

ConvertTo converts the histogram bucket values into `Tp`.

func (*Histogram) Copy 

func (hg *Histogram) Copy() *Histogram

Copy deep copies the histogram.

func (*Histogram) DecodeTo 

func (hg *Histogram) DecodeTo(tp *types.FieldType, timeZone *time.Location) error

DecodeTo decodes the histogram bucket values into `Tp`.

func (*Histogram) GetIncreaseFactor 

func (hg *Histogram) GetIncreaseFactor(totalCount int64) float64

GetIncreaseFactor will return a factor of data increasing after the last analysis.

func (*Histogram) GetLower 

func (hg *Histogram) GetLower(idx int) *types.Datum

GetLower gets the lower bound of bucket `idx`.

func (*Histogram) GetUpper 

func (hg *Histogram) GetUpper(idx int) *types.Datum

GetUpper gets the upper bound of bucket `idx`.

func (*Histogram) IsIndexHist 

func (hg *Histogram) IsIndexHist() bool

IsIndexHist checks whether current histogram is one for index.

func (*Histogram) Len 

func (hg *Histogram) Len() int

Len is the number of buckets in the histogram.

func (*Histogram) LessRowCountWithBktIdx 

func (hg *Histogram) LessRowCountWithBktIdx(value types.Datum) (float64, int)

LessRowCountWithBktIdx estimates the row count where the column less than value.

func (*Histogram) PreCalculateScalar 

func (hg *Histogram) PreCalculateScalar()

PreCalculateScalar converts the lower and upper to scalar. When the datum type is KindString or KindBytes, we also calculate their common prefix length, because when a value falls between lower and upper, the common prefix of lower and upper equals to the common prefix of the lower, upper and the value. For some simple types like `Int64`, we do not convert it because we can directly infer the scalar value.

func (*Histogram) RemoveUpperBound 

func (hg *Histogram) RemoveUpperBound() *Histogram

RemoveUpperBound removes the upper bound from histogram. It is used when merge stats for incremental analyze.

func (*Histogram) SplitRange 

func (hg *Histogram) SplitRange(sc *stmtctx.StatementContext, oldRanges []*ranger.Range, encoded bool) ([]*ranger.Range, bool)

SplitRange splits the range according to the histogram upper bound. Note that we treat last bucket's upper bound as inf, so all the split Ranges will totally fall in one of the (-inf, u(0)], (u(0), u(1)],...(u(n-3), u(n-2)], (u(n-2), +inf), where n is the number of buckets, u(i) is the i-th bucket's upper bound.

func (*Histogram) ToString 

func (hg *Histogram) ToString(idxCols int) string

ToString gets the string representation for the histogram.

func (*Histogram) TotalRowCount 

func (hg *Histogram) TotalRowCount() float64

TotalRowCount returns the total count of this histogram.

func (*Histogram) TruncateHistogram 

func (hg *Histogram) TruncateHistogram(numBkt int) *Histogram

TruncateHistogram truncates the histogram to `numBkt` buckets.

type Index 

type Index struct {
	Histogram
	*CMSketch
	ErrorRate
	StatsVer       int64 // StatsVer is the version of the current stats, used to maintain compatibility
	Info           *model.IndexInfo
	Flag           int64
	LastAnalyzePos types.Datum
}

Index represents an index histogram.

func (*Index) GetRowCount 

func (idx *Index) GetRowCount(sc *stmtctx.StatementContext, indexRanges []*ranger.Range, modifyCount int64) (float64, error)

GetRowCount returns the row count of the given ranges. It uses the modifyCount to adjust the influence of modifications on the table.

func (*Index) IsInvalid 

func (idx *Index) IsInvalid(collPseudo bool) bool

IsInvalid checks if this index is invalid.

func (*Index) String 

func (idx *Index) String() string

type QueryFeedback 

type QueryFeedback struct {
	PhysicalID int64
	Hist       *Histogram
	Tp         int
	Feedback   []Feedback
	Expected   int64 // Expected is the Expected scan count of corresponding query.

	Valid bool // Valid represents the whether this query feedback is still Valid.
	// contains filtered or unexported fields
}

QueryFeedback is used to represent the query feedback info. It contains the query's scan ranges and number of rows in each range.

func NewQueryFeedback 

func NewQueryFeedback(physicalID int64, hist *Histogram, expected int64, desc bool) *QueryFeedback

NewQueryFeedback returns a new query feedback.

func (*QueryFeedback) Actual 

func (q *QueryFeedback) Actual() int64

Actual gets the actual row count.

func (*QueryFeedback) CalcErrorRate 

func (q *QueryFeedback) CalcErrorRate() float64

CalcErrorRate calculates the error rate the current QueryFeedback.

func (*QueryFeedback) CollectFeedback 

func (q *QueryFeedback) CollectFeedback(numOfRanges int) bool

CollectFeedback decides whether to collect the feedback. It returns false when: 1: the histogram is nil or has no buckets; 2: the number of scan ranges exceeds the limit because it may affect the performance; 3: it does not pass the probabilistic sampler.

func (*QueryFeedback) DecodeIntValues 

func (q *QueryFeedback) DecodeIntValues() *QueryFeedback

DecodeIntValues is called when the current Feedback stores encoded int values.

func (*QueryFeedback) DecodeToRanges 

func (q *QueryFeedback) DecodeToRanges(isIndex bool) ([]*ranger.Range, error)

DecodeToRanges decode the feedback to ranges.

func (*QueryFeedback) Invalidate 

func (q *QueryFeedback) Invalidate()

Invalidate is used to invalidate the query feedback.

func (*QueryFeedback) StoreRanges 

func (q *QueryFeedback) StoreRanges(ranges []*ranger.Range)

StoreRanges stores the ranges for update.

func (*QueryFeedback) Update 

func (q *QueryFeedback) Update(startKey kv.Key, counts []int64)

Update updates the query feedback. `startKey` is the start scan key of the partial result, used to find the range for update. `counts` is the scan counts of each range, used to update the feedback count info.

type SampleBuilder 

type SampleBuilder struct {
	Sc              *stmtctx.StatementContext
	RecordSet       sqlexec.RecordSet
	ColLen          int // ColLen is the number of columns need to be sampled.
	PkBuilder       *SortedBuilder
	MaxBucketSize   int64
	MaxSampleSize   int64
	MaxFMSketchSize int64
	CMSketchDepth   int32
	CMSketchWidth   int32
}

SampleBuilder is used to build samples for columns. Also, if primary key is handle, it will directly build histogram for it.

func (SampleBuilder) CollectColumnStats 

func (s SampleBuilder) CollectColumnStats() ([]*SampleCollector, *SortedBuilder, error)

CollectColumnStats collects sample from the result set using Reservoir Sampling algorithm, and estimates NDVs using FM Sketch during the collecting process. It returns the sample collectors which contain total count, null count, distinct values count and CM Sketch. It also returns the statistic builder for PK which contains the histogram. See https://en.wikipedia.org/wiki/Reservoir_sampling

type SampleCollector 

type SampleCollector struct {
	Samples []*SampleItem

	IsMerger      bool
	NullCount     int64
	Count         int64 // Count is the number of non-null rows.
	MaxSampleSize int64
	FMSketch      *FMSketch
	CMSketch      *CMSketch
	TotalSize     int64 // TotalSize is the total size of column.
	// contains filtered or unexported fields
}

SampleCollector will collect Samples and calculate the count and ndv of an attribute.

func SampleCollectorFromProto 

func SampleCollectorFromProto(collector *tipb.SampleCollector) *SampleCollector

SampleCollectorFromProto converts SampleCollector from its protobuf representation.

func (*SampleCollector) CalcTotalSize 

func (c *SampleCollector) CalcTotalSize()

CalcTotalSize is to calculate total size based on samples.

func (*SampleCollector) MergeSampleCollector 

func (c *SampleCollector) MergeSampleCollector(sc *stmtctx.StatementContext, rc *SampleCollector)

MergeSampleCollector merges two sample collectors.

type SampleItem 

type SampleItem struct {
	// Value is the sampled column value.
	Value types.Datum
	// Ordinal is original position of this item in SampleCollector before sorting. This
	// is used for computing correlation.
	Ordinal int
	// RowID is the row id of the sample in its key.
	// This property is used to calculate Ordinal in fast analyze.
	RowID int64
}

SampleItem is an item of sampled column value.

type SortedBuilder 

type SortedBuilder struct {
	Count int64
	// contains filtered or unexported fields
}

SortedBuilder is used to build histograms for PK and index.

func NewSortedBuilder 

func NewSortedBuilder(sc *stmtctx.StatementContext, numBuckets, id int64, tp *types.FieldType) *SortedBuilder

NewSortedBuilder creates a new SortedBuilder.

func (*SortedBuilder) Hist 

func (b *SortedBuilder) Hist() *Histogram

Hist returns the histogram built by SortedBuilder.

func (*SortedBuilder) Iterate 

func (b *SortedBuilder) Iterate(data types.Datum) error

Iterate updates the histogram incrementally.

type StatsNode 

type StatsNode struct {
	Tp int
	ID int64

	// Ranges contains all the Ranges we got.
	Ranges []*ranger.Range
	// Selectivity indicates the Selectivity of this column/index.
	Selectivity float64
	// contains filtered or unexported fields
}

StatsNode is used for calculating selectivity.

type Table 

type Table struct {
	HistColl
	Version uint64
	Name    string
}

Table represents statistics for a table.

func PseudoTable 

func PseudoTable(tblInfo *model.TableInfo) *Table

PseudoTable creates a pseudo table statistics.

func (*Table) ColumnBetweenRowCount 

func (t *Table) ColumnBetweenRowCount(sc *stmtctx.StatementContext, a, b types.Datum, colID int64) float64

ColumnBetweenRowCount estimates the row count where column greater or equal to a and less than b.

func (*Table) ColumnByName 

func (t *Table) ColumnByName(colName string) *Column

ColumnByName finds the statistics.Column for the given column.

func (*Table) ColumnEqualRowCount 

func (t *Table) ColumnEqualRowCount(sc *stmtctx.StatementContext, value types.Datum, colID int64) (float64, error)

ColumnEqualRowCount estimates the row count where the column equals to value.

func (*Table) ColumnGreaterRowCount 

func (t *Table) ColumnGreaterRowCount(sc *stmtctx.StatementContext, value types.Datum, colID int64) float64

ColumnGreaterRowCount estimates the row count where the column greater than value.

func (*Table) ColumnLessRowCount 

func (t *Table) ColumnLessRowCount(sc *stmtctx.StatementContext, value types.Datum, colID int64) float64

ColumnLessRowCount estimates the row count where the column less than value. Note that null values are not counted.

func (*Table) Copy 

func (t *Table) Copy() *Table

Copy copies the current table.

func (*Table) IndexStartWithColumn 

func (t *Table) IndexStartWithColumn(colName string) *Index

IndexStartWithColumn finds the first index whose first column is the given column.

func (*Table) IsOutdated 

func (t *Table) IsOutdated() bool

IsOutdated returns true if the table stats is outdated.

func (*Table) PseudoAvgCountPerValue 

func (t *Table) PseudoAvgCountPerValue() float64

PseudoAvgCountPerValue gets a pseudo average count if histogram not exists.

func (*Table) String 

func (t *Table) String() string

String implements Stringer interface.

type TopNMeta 

type TopNMeta struct {
	Data  []byte
	Count uint64
	// contains filtered or unexported fields
}

TopNMeta is a simple counter used by BuildTopN.

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