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Diffstat (limited to '')
-rw-r--r-- | dependencies/pkg/mod/github.com/mattn/go-sqlite3@v1.14.16/_example/custom_func/main.go | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/github.com/mattn/go-sqlite3@v1.14.16/_example/custom_func/main.go b/dependencies/pkg/mod/github.com/mattn/go-sqlite3@v1.14.16/_example/custom_func/main.go new file mode 100644 index 0000000..85657e6 --- /dev/null +++ b/dependencies/pkg/mod/github.com/mattn/go-sqlite3@v1.14.16/_example/custom_func/main.go @@ -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) + } +} |