mirror of
https://github.com/ncruces/go-sqlite3.git
synced 2026-01-12 05:59:14 +00:00
97 lines
2.1 KiB
Go
97 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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const (
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median = iota
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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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// Implementing inverse allows certain queries that don't really need it to succeed.
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ctx.ResultError(util.ErrorString("percentile: may not be used as a window function"))
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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 = getPercentile(q.nums, 0.5, false)
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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 = getPercentile(q.nums, float, q.kind == percentile_disc)
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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 = getPercentiles(q.nums, floats, q.kind == percentile_disc)
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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 getPercentile(nums []float64, pos float64, disc bool) (float64, error) {
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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(nums)-1))
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m0 := quick.Select(nums, int(i))
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if f == 0 || disc {
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return m0, nil
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}
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m1 := slices.Min(nums[int(i)+1:])
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return math.FMA(f, m1, math.FMA(-f, m0, m0)), nil
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}
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func getPercentiles(nums []float64, pos []float64, disc bool) error {
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for i := range pos {
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v, err := getPercentile(nums, pos[i], disc)
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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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