mirror of
https://github.com/ncruces/go-sqlite3.git
synced 2026-01-12 14:09:13 +00:00
110 lines
2.1 KiB
Go
110 lines
2.1 KiB
Go
package stats
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import (
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"encoding/json"
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"fmt"
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"math"
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"slices"
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"github.com/ncruces/go-sqlite3"
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"github.com/ncruces/go-sqlite3/internal/util"
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"github.com/ncruces/sort/quick"
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)
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// Compatible with:
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// https://sqlite.org/src/file/ext/misc/percentile.c
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const (
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median = iota
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percentile_100
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percentile_cont
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percentile_disc
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)
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func newPercentile(kind int) func() sqlite3.AggregateFunction {
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return func() sqlite3.AggregateFunction { return &percentile{kind: kind} }
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}
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type percentile struct {
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nums []float64
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arg1 []byte
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kind int
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}
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func (q *percentile) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
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a := arg[0]
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f := a.Float()
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if f != 0.0 || a.NumericType() != sqlite3.NULL {
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q.nums = append(q.nums, f)
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}
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if q.kind != median && q.arg1 == nil {
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q.arg1 = append(q.arg1, arg[1].RawText()...)
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}
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}
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func (q *percentile) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
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a := arg[0]
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f := a.Float()
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if f != 0.0 || a.NumericType() != sqlite3.NULL {
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i := slices.Index(q.nums, f)
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l := len(q.nums) - 1
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q.nums[i] = q.nums[l]
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q.nums = q.nums[:l]
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}
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}
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func (q *percentile) Value(ctx sqlite3.Context) {
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if len(q.nums) == 0 {
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return
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}
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var (
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err error
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float float64
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floats []float64
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)
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if q.kind == median {
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float, err = q.at(0.5)
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ctx.ResultFloat(float)
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} else if err = json.Unmarshal(q.arg1, &float); err == nil {
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float, err = q.at(float)
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ctx.ResultFloat(float)
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} else if err = json.Unmarshal(q.arg1, &floats); err == nil {
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err = q.atMore(floats)
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ctx.ResultJSON(floats)
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}
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if err != nil {
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ctx.ResultError(fmt.Errorf("percentile: %w", err)) // notest
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}
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}
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func (q *percentile) at(pos float64) (float64, error) {
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if q.kind == percentile_100 {
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pos = pos / 100
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}
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if pos < 0 || pos > 1 {
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return 0, util.ErrorString("invalid pos")
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}
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i, f := math.Modf(pos * float64(len(q.nums)-1))
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m0 := quick.Select(q.nums, int(i))
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if f == 0 || q.kind == percentile_disc {
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return m0, nil
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}
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m1 := slices.Min(q.nums[int(i)+1:])
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return util.Lerp(m0, m1, f), nil
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}
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func (q *percentile) atMore(pos []float64) error {
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for i := range pos {
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v, err := q.at(pos[i])
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if err != nil {
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return err
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}
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pos[i] = v
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}
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return nil
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}
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