statistics

package
Version: v1.0.0 Latest Latest
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Published: Oct 16, 2017 License: Apache-2.0 Imports: 28 Imported by: 0

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Index

Constants

View Source
const (
	// StatsOwnerKey is the stats owner path that is saved to etcd.
	StatsOwnerKey = "/tidb/stats/owner"
	// StatsPrompt is the prompt for stats owner manager.
	StatsPrompt = "stats"
)

Variables

This section is empty.

Functions

func FMSketchToProto

func FMSketchToProto(s *FMSketch) *tipb.FMSketch

FMSketchToProto converts FMSketch to its protobuf representation.

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 SampleCollectorToProto

func SampleCollectorToProto(c *SampleCollector) *tipb.SampleCollector

SampleCollectorToProto converts SampleCollector to its protobuf representation.

Types

type AnalyzeResult

type AnalyzeResult struct {
	TableID int64
	Hist    []*Histogram
	Count   int64
	IsIndex int
	Err     error
}

AnalyzeResult is used to represent analyze result.

type Bucket

type Bucket struct {
	Count      int64
	UpperBound types.Datum
	LowerBound types.Datum
	Repeats    int64
	// contains filtered or unexported fields
}

Bucket is an element of histogram.

A bucket count is the number of items stored in all previous buckets and the current bucket. bucket numbers are always in increasing order.

A bucket value is the greatest item value stored in the bucket.

Repeat is the number of repeats of the bucket value, it can be used to find popular values.

type Column

type Column struct {
	Histogram
	Info *model.ColumnInfo
}

Column represents a column histogram.

func (*Column) String

func (c *Column) String() string

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(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 Handle

type Handle struct {

	// LastVersion is the latest update version before last lease. Exported for test.
	LastVersion uint64
	// PrevLastVersion is the latest update version before two lease. Exported for test.
	// We need this because for two tables, the smaller version may write later than the one with larger version.
	// We can read the version with lastTwoVersion if the diff between commit time and version is less than one lease.
	// PrevLastVersion will be assigned by LastVersion every time Update is called.
	PrevLastVersion uint64

	Lease time.Duration
	// contains filtered or unexported fields
}

Handle can update stats info periodically.

func NewHandle

func NewHandle(ctx context.Context, lease time.Duration) *Handle

NewHandle creates a Handle for update stats.

func (*Handle) AnalyzeResultCh

func (h *Handle) AnalyzeResultCh() chan *AnalyzeResult

AnalyzeResultCh returns analyze result channel in handle.

func (*Handle) Clear

func (h *Handle) Clear()

Clear the statsCache, only for test.

func (*Handle) DDLEventCh

func (h *Handle) DDLEventCh() chan *ddl.Event

DDLEventCh returns ddl events channel in handle.

func (*Handle) DeleteTableStatsFromKV

func (h *Handle) DeleteTableStatsFromKV(id int64) error

DeleteTableStatsFromKV deletes table statistics from kv.

func (*Handle) DumpStatsDeltaToKV

func (h *Handle) DumpStatsDeltaToKV()

DumpStatsDeltaToKV sweeps the whole list and updates the global map. Then we dumps every table that held in map to KV.

func (*Handle) GetTableStats

func (h *Handle) GetTableStats(tblID int64) *Table

GetTableStats retrieves the statistics table from cache, and the cache will be updated by a goroutine.

func (*Handle) HandleAutoAnalyze

func (h *Handle) HandleAutoAnalyze(is infoschema.InfoSchema) error

HandleAutoAnalyze analyzes the newly created table or index.

func (*Handle) HandleDDLEvent

func (h *Handle) HandleDDLEvent(t *ddl.Event) error

HandleDDLEvent begins to process a ddl task.

func (*Handle) NewSessionStatsCollector

func (h *Handle) NewSessionStatsCollector() *SessionStatsCollector

NewSessionStatsCollector allocates a stats collector for a session.

func (*Handle) Update

func (h *Handle) Update(is infoschema.InfoSchema) error

Update reads stats meta from store and updates the stats map.

func (*Handle) UpdateTableStats

func (h *Handle) UpdateTableStats(tables []*Table, deletedIDs []int64)

UpdateTableStats updates the statistics table cache using copy on write.

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

	Buckets []Bucket
}

Histogram represents statistics for a column or index.

func BuildColumn

func BuildColumn(ctx context.Context, numBuckets, id int64, collector *SampleCollector) (*Histogram, error)

BuildColumn builds histogram from samples for column.

func BuildIndex

func BuildIndex(ctx context.Context, numBuckets, id int64, records ast.RecordSet) (int64, *Histogram, error)

BuildIndex builds histogram for index.

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 *variable.StatementContext, lh *Histogram, rh *Histogram, bucketSize int) (*Histogram, error)

MergeHistograms merges two histograms.

func (*Histogram) SaveToStorage

func (hg *Histogram) SaveToStorage(ctx context.Context, tableID int64, count int64, isIndex int) error

SaveToStorage saves the histogram to storage.

type Index

type Index struct {
	Histogram
	Info *model.IndexInfo
}

Index represents an index histogram.

func (*Index) String

func (idx *Index) String() string

type SampleBuilder

type SampleBuilder struct {
	Sc            *variable.StatementContext
	RecordSet     ast.RecordSet
	ColLen        int   // ColLen is the number of columns need to be sampled.
	PkID          int64 // If primary key is handle, the PkID is the id of the primary key. If not exists, it is -1.
	MaxBucketSize int64
	MaxSampleSize int64
	MaxSketchSize int64
}

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

func (SampleBuilder) CollectSamplesAndEstimateNDVs

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

CollectSamplesAndEstimateNDVs 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 and distinct values count. 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 []types.Datum

	IsMerger      bool
	NullCount     int64
	Count         int64 // Count is the number of non-null rows.
	MaxSampleSize int64
	Sketch        *FMSketch
	// 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) MergeSampleCollector

func (c *SampleCollector) MergeSampleCollector(rc *SampleCollector)

MergeSampleCollector merges two sample collectors.

type SessionStatsCollector

type SessionStatsCollector struct {
	sync.Mutex
	// contains filtered or unexported fields
}

SessionStatsCollector is a list item that holds the delta mapper. If you want to write or read mapper, you must lock it.

func (*SessionStatsCollector) Delete

func (s *SessionStatsCollector) Delete()

Delete only sets the deleted flag true, it will be deleted from list when DumpStatsDeltaToKV is called.

func (*SessionStatsCollector) Update

func (s *SessionStatsCollector) Update(id int64, delta int64, count int64)

Update will updates the delta and count for one table id.

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 *variable.StatementContext, numBuckets, id int64) *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 Table

type Table struct {
	TableID     int64
	Columns     map[int64]*Column
	Indices     map[int64]*Index
	Count       int64 // Total row count in a table.
	ModifyCount int64 // Total modify count in a table.
	Version     uint64
	Pseudo      bool
}

Table represents statistics for a table.

func PseudoTable

func PseudoTable(tableID int64) *Table

PseudoTable creates a pseudo table statistics when statistic can not be found in KV store.

func (*Table) ColumnBetweenRowCount

func (t *Table) ColumnBetweenRowCount(sc *variable.StatementContext, a, b types.Datum, colInfo *model.ColumnInfo) (float64, error)

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

func (*Table) ColumnEqualRowCount

func (t *Table) ColumnEqualRowCount(sc *variable.StatementContext, value types.Datum, colInfo *model.ColumnInfo) (float64, error)

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

func (*Table) ColumnGreaterRowCount

func (t *Table) ColumnGreaterRowCount(sc *variable.StatementContext, value types.Datum, colInfo *model.ColumnInfo) (float64, error)

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

func (*Table) ColumnIsInvalid

func (t *Table) ColumnIsInvalid(colInfo *model.ColumnInfo) bool

ColumnIsInvalid checks if this column is invalid.

func (*Table) ColumnLessRowCount

func (t *Table) ColumnLessRowCount(sc *variable.StatementContext, value types.Datum, colInfo *model.ColumnInfo) (float64, error)

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

func (*Table) GetRowCountByColumnRanges

func (t *Table) GetRowCountByColumnRanges(sc *variable.StatementContext, colID int64, colRanges []*types.ColumnRange) (float64, error)

GetRowCountByColumnRanges estimates the row count by a slice of ColumnRange.

func (*Table) GetRowCountByIndexRanges

func (t *Table) GetRowCountByIndexRanges(sc *variable.StatementContext, idxID int64, indexRanges []*types.IndexRange) (float64, error)

GetRowCountByIndexRanges estimates the row count by a slice of IndexRange.

func (*Table) GetRowCountByIntColumnRanges

func (t *Table) GetRowCountByIntColumnRanges(sc *variable.StatementContext, colID int64, intRanges []types.IntColumnRange) (float64, error)

GetRowCountByIntColumnRanges estimates the row count by a slice of IntColumnRange.

func (*Table) Selectivity

func (t *Table) Selectivity(ctx context.Context, exprs []expression.Expression) (float64, 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. TODO: support expressions that the top layer is a DNF. Currently the time complexity is o(n^2).

func (*Table) String

func (t *Table) String() string

String implements Stringer interface.

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