Get after a Merge will throw a segmentation violation

[mijia]

Hi,

I am trying to wrap rocksdb inside my Go code and your wrapper is a great library. But I got a segmentation violation fatal error when "Get" after a single "Merge" call with a fresh database.

The code to reproduce this is,

package main

import (
    rocks "github.com/tecbot/gorocksdb"
    "fmt"
    "runtime"
    "sync"
)

type Handler struct {}

func (h *Handler) FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool) {
    fmt.Println("FullMerge called.")
    for _, operand := range operands {
        existingValue = append(existingValue, operand...)
    }
    return existingValue, true
}

func (h *Handler) PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool) {
    return nil, false
}

func (h *Handler) Name() string {
    return "GoRockdisMergeOperator"
}


func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())

    opts := rocks.NewDefaultOptions()
    opts.SetCreateIfMissing(true)
    opts.SetMergeOperator(rocks.NewMergeOperator(&Handler{}))

    db, err := rocks.OpenDb(opts, "/opt/tmp/rocksdb")
    if err != nil {
        panic(err)
    }

    var wg sync.WaitGroup
    wg.Add(1)
    go func() {
        ro := rocks.NewDefaultReadOptions()
        wo := rocks.NewDefaultWriteOptions()

        err = db.Merge(wo, []byte("test"), []byte("hello"))
        if err != nil {
            panic(err)
        }

        data, err := db.Get(ro, []byte("test"))
        if err != nil {
            panic(err)
        }
        fmt.Println(string(data.Data()))
        wg.Done()
    }()

    wg.Wait()
}

The error is,

SIGSEGV: segmentation violation
PC=0x420f339
signal arrived during cgo execution

runtime.cgocall(0x40011b0, 0x4491e28)
    /usr/local/Cellar/go/1.2/libexec/src/pkg/runtime/cgocall.c:149 +0x11b fp=0x4491e10
github.com/tecbot/gorocksdb._Cfunc_rocksdb_get(0x4513e50, 0x4505350, 0xc210000068, 0x4, 0xc210000078, ...)
    github.com/tecbot/gorocksdb/_obj/_cgo_defun.c:318 +0x36 fp=0x4491e28
github.com/tecbot/gorocksdb.(*DB).Get(0xc21004d000, 0xc210000040, 0xc210000068, 0x4, 0x4, ...)
    /Users/mijia/Projects/sandbox/gocode/src/github.com/tecbot/gorocksdb/db.go:55 +0xf0 fp=0x4491ea8
main.func·001()
    /Users/mijia/Projects/sandbox/gocode/src/github.com/mijia/gorockdis/test/merge_fail.go:52 +0x266 fp=0x4491fa0
...

I am using Mac OS 10.9.1, any clue for this?
Thank you very much.

[tecbot]

Hi mijia,

thank you for reporting this failing behavior. I fixed the problem in the C API and added a test case for this. You should pull the new master from the C lib and try again.

Thomas

[mijia]

Hi Thomas,

Awesome, got the updates and really fix the problem.
Thank you so much.