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Window percentil.

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This commit is contained in:
Nuno Cruces
2024-10-17 08:15:44 +01:00
parent c78d00dca0
commit 50c8517603
3 changed files with 63 additions and 23 deletions
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20
ext/stats/boolean.go
View File

@@ -26,21 +26,21 @@ func (b *boolean) Value(ctx sqlite3.Context) {
}
func (b *boolean) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
if arg[0].Type() == sqlite3.NULL {
return
}
if arg[0].Bool() {
a := arg[0]
if a.Bool() {
b.count++
}
b.total++
if a.Type() != sqlite3.NULL {
b.total++
}
}
func (b *boolean) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
if arg[0].Type() == sqlite3.NULL {
return
}
if arg[0].Bool() {
a := arg[0]
if a.Bool() {
b.count--
}
b.total--
if a.Type() != sqlite3.NULL {
b.total--
}
}

32
ext/stats/percentile.go
View File

@@ -40,8 +40,14 @@ func (q *percentile) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
}
func (q *percentile) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
// Implementing inverse allows certain queries that don't really need it to succeed.
ctx.ResultError(util.ErrorString("percentile: may not be used as a window function"))
a := arg[0]
f := a.Float()
if f != 0.0 || a.NumericType() != sqlite3.NULL {
i := slices.Index(q.nums, f)
l := len(q.nums) - 1
q.nums[i] = q.nums[l]
q.nums = q.nums[:l]
}
}
func (q *percentile) Value(ctx sqlite3.Context) {
@@ -55,13 +61,13 @@ func (q *percentile) Value(ctx sqlite3.Context) {
floats []float64
)
if q.kind == median {
float, err = getPercentile(q.nums, 0.5, q.kind)
float, err = q.at(0.5)
ctx.ResultFloat(float)
} else if err = json.Unmarshal(q.arg1, &float); err == nil {
float, err = getPercentile(q.nums, float, q.kind)
float, err = q.at(float)
ctx.ResultFloat(float)
} else if err = json.Unmarshal(q.arg1, &floats); err == nil {
err = getPercentiles(q.nums, floats, q.kind)
err = q.atMore(floats)
ctx.ResultJSON(floats)
}
if err != nil {
@@ -69,28 +75,28 @@ func (q *percentile) Value(ctx sqlite3.Context) {
}
}
func getPercentile(nums []float64, pos float64, kind int) (float64, error) {
if kind == percentile_100 {
func (q *percentile) at(pos float64) (float64, error) {
if q.kind == percentile_100 {
pos = pos / 100
}
if pos < 0 || pos > 1 {
return 0, util.ErrorString("invalid pos")
}
i, f := math.Modf(pos * float64(len(nums)-1))
m0 := quick.Select(nums, int(i))
i, f := math.Modf(pos * float64(len(q.nums)-1))
m0 := quick.Select(q.nums, int(i))
if f == 0 || kind == percentile_disc {
if f == 0 || q.kind == percentile_disc {
return m0, nil
}
m1 := slices.Min(nums[int(i)+1:])
m1 := slices.Min(q.nums[int(i)+1:])
return math.FMA(f, m1, math.FMA(-f, m0, m0)), nil
}
func getPercentiles(nums []float64, pos []float64, kind int) error {
func (q *percentile) atMore(pos []float64) error {
for i := range pos {
v, err := getPercentile(nums, pos[i], kind)
v, err := q.at(pos[i])
if err != nil {
return err
}

34
ext/stats/percentile_test.go
View File

@@ -58,6 +58,40 @@ func TestRegister_percentile(t *testing.T) {
}
stmt.Close()
stmt, _, err = db.Prepare(`
SELECT
median(x) OVER (ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
FROM data`)
if err != nil {
t.Fatal(err)
}
if stmt.Step() {
if got := stmt.ColumnFloat(0); got != 5.5 {
t.Errorf("got %v, want 5.5", got)
}
}
if stmt.Step() {
if got := stmt.ColumnFloat(0); got != 7 {
t.Errorf("got %v, want 7", got)
}
}
if stmt.Step() {
if got := stmt.ColumnFloat(0); got != 10 {
t.Errorf("got %v, want 10", got)
}
}
if stmt.Step() {
if got := stmt.ColumnFloat(0); got != 14.5 {
t.Errorf("got %v, want 14.5", got)
}
}
if stmt.Step() {
if got := stmt.ColumnFloat(0); got != 16 {
t.Errorf("got %v, want 16", got)
}
}
stmt.Close()
stmt, _, err = db.Prepare(`
SELECT
median(x),