Data race in Insert()

[pwaller]

The race detector just found a race in my web app.

My code is really very straightforward. What I'm doing amounts to this:

package db

import "time"

type Foo struct {
    Id       string    `db:"id"`
}

func InsertFoo() error {
    return dbmap.Insert(&p)
}

// Call InsertFoo from a web handler.

==================
WARNING: DATA RACE
Read by goroutine 65:
  x/vendor/github.com/go-gorp/gorp.(*TableMap).bindInsert()
      /go/src/x/vendor/github.com/go-gorp/gorp/table_bindings.go:103 +0x8b
  x/vendor/github.com/go-gorp/gorp.insert()
      /go/src/x/vendor/github.com/go-gorp/gorp/gorp.go:505 +0x2f4
  x/vendor/github.com/go-gorp/gorp.(*DbMap).Insert()

Previous write by goroutine 86:
  x/vendor/github.com/go-gorp/gorp.(*TableMap).bindInsert()
      /go/src/x/vendor/github.com/go-gorp/gorp/table_bindings.go:157 +0x942
  x/vendor/github.com/go-gorp/gorp.insert()
      /go/src/x/vendor/github.com/go-gorp/gorp/gorp.go:505 +0x2f4
  x/vendor/github.com/go-gorp/gorp.(*DbMap).Insert()
      /go/src/x/vendor/github.com/go-gorp/gorp/db.go:395 +0x99

I'm surprised that I could be the first person to report a race bug here.

The report suggests this line:

gorp/table_bindings.go

Line 103 in 75d359a

plan := t.insertPlan

Is racing against this line:

gorp/table_bindings.go

Line 157 in 75d359a

t.insertPlan = plan

Am I misusing Insert? I did not realise anywhere from the documentation that I would have to lock the DbMap during inserts.

The Insert docs don't mention anything about concurrency:

https://godoc.org/gopkg.in/gorp.v1#DbMap.Insert

And the DbMap docs suggest that I only have to make one per schema, not per request:

https://godoc.org/gopkg.in/gorp.v1#DbMap

Thoughts?

[pwaller]

Also, I want to mention that I have using this exact code with the race detector switched on many times daily for a month, and just now is the first time I saw it fire. I've been using the same pattern all over my code (Insert from goroutines handling web requests) for a year and I haven't seen it fire there either. So maybe this is particularly hard for the race detector to spot for some reason?

[GeertJohan]

Fixed by #301