statistics

type ColumnStatistics struct {
	ColumnName  string
	RowCount    uint64
	NullCount   uint64
	Cardinality uint64
	LastUpdated int64
	MinVal      interface{}
	MaxVal      interface{}
	Histogram   Histogram // Histogram
}

type Histogram interface {
	// EstimateSelectivity estimates the selectivity of a given expression.
	EstimateSelectivity(expr influxql.Expr) float64

	// Update updates the histogram with a set of values.
	Update(values ...interface{})

	// Serialize serializes the histogram into a byte slice.
	Serialize() ([]byte, error)

	// Deserialize deserializes the histogram from a byte slice.
	Deserialize(data []byte) error
}

type JoinStatistics struct {
	LeftRows      uint64
	RightRows     uint64
	EstimatedRows uint64  // Estimated number of join result rows
	Selectivity   float64 // Selectivity
}

type NumericBin struct {
	Min     float64
	Max     float64
	Count   uint64
	Density float64
}

type NumericHistogram struct {
	Bins       []NumericBin // sorted by Min Max value
	TotalCount uint64
	Name       string
}

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

type StatisticsProvider interface {
	// GetTableStats retrieves table-level statistics for a given measurement.
	GetTableStats(measurement string) (*TableStatistics, error)

	// GetColumnStats retrieves column-level statistics for a specified measurement and column.
	GetColumnStats(measurement, column string) (*ColumnStatistics, error)

	// GetTagStats retrieves tag-level statistics for a specified measurement and tag.
	GetTagStats(measurement, tag string) (*TagStatistics, error)

	// GetJoinStats retrieves join operation statistics for specified left and right measurements with a condition.
	GetJoinStats(left, right string, condition influxql.Expr) (*JoinStatistics, error)

	// UpdateTableStats updates the table-level statistics for a given measurement.
	UpdateTableStats(measurement string, stats *TableStatistics) error

	// UpdateColumnStats updates the column-level statistics for a specified measurement and column.
	UpdateColumnStats(measurement, column string, stats *ColumnStatistics) error

	// UpdateTagStats updates the tag-level statistics for a specified measurement and tag.
	UpdateTagStats(measurement, tag string, stats *TagStatistics) error

	// SaveToStorage persists the statistical information to storage.
	SaveToStorage() error

	// LoadFromStorage loads the statistical information from storage.
	LoadFromStorage() error
}

type TableStatistics struct {
	Measurement   string
	RowCount      uint64
	LastUpdated   int64
	TagCount      int             // Number of tags
	FieldCount    int             // Number of fields
	SeriesCount   uint64          // Number of series
	AvgSeriesSize float64         // Average series size
	TimeRange     *TimeRangeStats // Time range statistics
}

type TagStatistics struct {
	TagName     string
	Cardinality uint64 // Cardinality
	LastUpdated int64
	TopValues   []TagValueFreq // Top values
}

type TagValueFreq struct {
	Value interface{}
	Freq  float64 // Frequency proportion
	Count uint64  // Count
}

type TimeRangeStats struct {
	MinTime     int64
	MaxTime     int64
	TimeSpan    time.Duration // Time span
	AvgInterval float64       // Average time interval (in seconds)
}