-
-
Notifications
You must be signed in to change notification settings - Fork 1.1k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Merge pull request #229 from danderson/master
Implement support for calling Go functions from SQLite
- Loading branch information
Showing
8 changed files
with
1,074 additions
and
9 deletions.
There are no files selected for viewing
Binary file not shown.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,133 @@ | ||
package main | ||
|
||
import ( | ||
"database/sql" | ||
"fmt" | ||
"log" | ||
"math" | ||
"math/rand" | ||
|
||
sqlite "github.com/mattn/go-sqlite3" | ||
) | ||
|
||
// Computes x^y | ||
func pow(x, y int64) int64 { | ||
return int64(math.Pow(float64(x), float64(y))) | ||
} | ||
|
||
// Computes the bitwise exclusive-or of all its arguments | ||
func xor(xs ...int64) int64 { | ||
var ret int64 | ||
for _, x := range xs { | ||
ret ^= x | ||
} | ||
return ret | ||
} | ||
|
||
// Returns a random number. It's actually deterministic here because | ||
// we don't seed the RNG, but it's an example of a non-pure function | ||
// from SQLite's POV. | ||
func getrand() int64 { | ||
return rand.Int63() | ||
} | ||
|
||
// Computes the standard deviation of a GROUPed BY set of values | ||
type stddev struct { | ||
xs []int64 | ||
// Running average calculation | ||
sum int64 | ||
n int64 | ||
} | ||
|
||
func newStddev() *stddev { return &stddev{} } | ||
|
||
func (s *stddev) Step(x int64) { | ||
s.xs = append(s.xs, x) | ||
s.sum += x | ||
s.n++ | ||
} | ||
|
||
func (s *stddev) Done() float64 { | ||
mean := float64(s.sum) / float64(s.n) | ||
var sqDiff []float64 | ||
for _, x := range s.xs { | ||
sqDiff = append(sqDiff, math.Pow(float64(x)-mean, 2)) | ||
} | ||
var dev float64 | ||
for _, x := range sqDiff { | ||
dev += x | ||
} | ||
dev /= float64(len(sqDiff)) | ||
return math.Sqrt(dev) | ||
} | ||
|
||
func main() { | ||
sql.Register("sqlite3_custom", &sqlite.SQLiteDriver{ | ||
ConnectHook: func(conn *sqlite.SQLiteConn) error { | ||
if err := conn.RegisterFunc("pow", pow, true); err != nil { | ||
return err | ||
} | ||
if err := conn.RegisterFunc("xor", xor, true); err != nil { | ||
return err | ||
} | ||
if err := conn.RegisterFunc("rand", getrand, false); err != nil { | ||
return err | ||
} | ||
if err := conn.RegisterAggregator("stddev", newStddev, true); err != nil { | ||
return err | ||
} | ||
return nil | ||
}, | ||
}) | ||
|
||
db, err := sql.Open("sqlite3_custom", ":memory:") | ||
if err != nil { | ||
log.Fatal("Failed to open database:", err) | ||
} | ||
defer db.Close() | ||
|
||
var i int64 | ||
err = db.QueryRow("SELECT pow(2,3)").Scan(&i) | ||
if err != nil { | ||
log.Fatal("POW query error:", err) | ||
} | ||
fmt.Println("pow(2,3) =", i) // 8 | ||
|
||
err = db.QueryRow("SELECT xor(1,2,3,4,5,6)").Scan(&i) | ||
if err != nil { | ||
log.Fatal("XOR query error:", err) | ||
} | ||
fmt.Println("xor(1,2,3,4,5) =", i) // 7 | ||
|
||
err = db.QueryRow("SELECT rand()").Scan(&i) | ||
if err != nil { | ||
log.Fatal("RAND query error:", err) | ||
} | ||
fmt.Println("rand() =", i) // pseudorandom | ||
|
||
_, err = db.Exec("create table foo (department integer, profits integer)") | ||
if err != nil { | ||
log.Fatal("Failed to create table:", err) | ||
} | ||
_, err = db.Exec("insert into foo values (1, 10), (1, 20), (1, 45), (2, 42), (2, 115)") | ||
if err != nil { | ||
log.Fatal("Failed to insert records:", err) | ||
} | ||
|
||
rows, err := db.Query("select department, stddev(profits) from foo group by department") | ||
if err != nil { | ||
log.Fatal("STDDEV query error:", err) | ||
} | ||
defer rows.Close() | ||
for rows.Next() { | ||
var dept int64 | ||
var dev float64 | ||
if err := rows.Scan(&dept, &dev); err != nil { | ||
log.Fatal(err) | ||
} | ||
fmt.Printf("dept=%d stddev=%f\n", dept, dev) | ||
} | ||
if err := rows.Err(); err != nil { | ||
log.Fatal(err) | ||
} | ||
} |
Oops, something went wrong.