我在提交事务时遇到了问题（使用Access 2003 DAO）。它好像从未调用过BeginTrans一样——在CommitTrans上我会得到3034错误，“您尝试在没有开始事务的情况下提交或回滚事务”；而更改被写入数据库（可能是因为它们从未包装在事务中）。然而，如果您逐步执行，则会运行BeginTrans 。
- 我正在使用DBEngine（0）工作区在Access环境中运行它。
- 我要添加记录的表都是通过Jet数据库连接打开的（连接到同一个数据库），并使用DAO.Recordset.AddNew / Update。
- 连接在开始BeforeTrans之前打开。
- 在事务中间我没有做任何奇怪的事情，如关闭/打开连接或多个工作区等。
- 有两个嵌套的事务级别。基本上，它将多个插入语句包装在外部事务中，因此如果有任何失败，它们都会失败。内部事务运行没有错误，是外部事务不起作用。
以下是我研究并排除的一些事项：
事务跨越了几种方法，并且BeginTrans和CommitTrans（以及Rollback）都在不同的位置。但当我尝试以这种方式运行事务的简单测试时，似乎这不应该有影响。
我想也许当它超出本地范围时，数据库连接会关闭，尽管我有另一个“全局”引用它（老实说，我从来不知道DAO如何处理数据库连接）。但是这似乎不是这种情况——在提交之前，连接及其记录集是活动的（我可以检查它们的属性，EOF = False等）
我的CommitTrans和Rollback是在事件回调中完成的。（非常基本地：解析器程序在解析结束时抛出“onLoad”事件，我通过根据是否发生任何错误来处理，在处理过程中插入或回滚。）然而，再次尝试简单测试，似乎这不应该有影响。
为什么我不能工作？
谢谢。
编辑5月25日
以下是（简化后的）代码。与事务有关的关键点是：
- 工作区是DBEngine（0），在公共（全局）变量
APPSESSION中引用。 - 数据库连接在下面的LoadProcess.cache中打开，请参见
Set db = APPSESSION.connectionTo(dbname_)行。 - BeginTrans在LoadProcess.cache中调用。
- CommitTrans在process__onLoad回调中调用。
- Rollback在process__onInvalid回调中调用。
- 记录集更新在process__onLoadRow、logLoadInit和logLoad中完成
Eric
'-------------------
'Application globals
'-------------------
Public APPSESSION As DAOSession
'------------------
' Class LoadProcess
'------------------
Private WithEvents process_ As EventedParser
Private errs_ As New Collection
Private dbname_ As String
Private rawtable_ As String
Private logtable_ As String
Private isInTrans_ As Integer
Private raw_ As DAO.Recordset
Private log_ As DAO.Recordset
Private logid_ As Variant
Public Sub run
'--- pre-load
cache
resetOnRun ' resets load state variables per run, omitted here
logLoadInit
Set process_ = New EventedParser
'--- load
process_.Load
End Sub
' raised once per load() if any row invalid
Public Sub process__onInvalid(filename As String)
If isInTrans_ Then APPSESSION.Workspace.Rollback
End Sub
' raised once per load() if all rows valid, after load
Public Sub process__onLoad(filename As String)
If errs_.Count > 0 Then
logLoadFail filename, errs_
Else
logLoadOK filename
End If
If isInTrans_ Then APPSESSION.Workspace.CommitTrans
End Sub
' raised once per valid row
' append data to raw_ recordset
Public Sub process__onLoadRow(row As Dictionary)
On Error GoTo Err_
If raw_ Is Nothing Then GoTo Exit_
DAOext.appendFromHash raw_, row, , APPSESSION.Workspace
Exit_:
Exit Sub
Err_:
' runtime error handling done here, code omitted
Resume Exit_
End Sub
Private Sub cache()
Dim db As DAO.Database
' TODO raise error
If Len(dbname_) = 0 Then GoTo Exit_
Set db = APPSESSION.connectionTo(dbname_)
' TODO raise error
If db Is Nothing Then GoTo Exit_
Set raw_ = db.OpenRecordset(rawtable_), dbOpenDynaset)
Set log_ = db.OpenRecordset(logtable_), dbOpenDynaset)
APPSESSION.Workspace.BeginTrans
isInTrans_ = True
Exit_:
Set db = Nothing
End Sub
' Append initial record to log table
Private Sub logLoadInit()
Dim info As New Dictionary
On Error GoTo Err_
' TODO raise error?
If log_ Is Nothing Then GoTo Exit_
With info
.add "loadTime", Now
.add "loadBy", CurrentUser
End With
logid_ = DAOext.appendFromHash(log_, info, , APPSESSION.Workspace)
Exit_:
Exit Sub
Err_:
' runtime error handling done here, code omitted
Resume Exit_
End Sub
Private Sub logLoadOK(filename As String)
logLoad logid_, True, filename, New Collection
End Sub
Private Sub logLoadFail(filename As String, _
errs As Collection)
logLoad logid_, False, filename, errs
End Sub
' Update log table record added in logLoadInit
Private Sub logLoad(logID As Variant, _
isloaded As Boolean, _
filename As String, _
errs As Collection)
Dim info As New Dictionary
Dim er As Variant, strErrs As String
Dim ks As Variant, k As Variant
On Error GoTo Err_
' TODO raise error?
If log_ Is Nothing Then GoTo Exit_
If IsNull(logID) Then GoTo Exit_
For Each er In errs
strErrs = strErrs & IIf(Len(strErrs) = 0, "", vbCrLf) & CStr(er)
Next Er
With info
.add "loadTime", Now
.add "loadBy", CurrentUser
.add "loadRecs", nrecs
.add "loadSuccess", isloaded
.add "loadErrs", strErrs
.add "origPath", filename
End With
log_.Requery
log_.FindFirst "[logID]=" & Nz(logID)
If log_.NoMatch Then
'TODO raise error
Else
log_.Edit
ks = info.Keys
For Each k In ks
log_.Fields(k).Value = info(k)
Next k
log_.Update
End If
Exit_:
Exit Sub
Err_:
' runtime error handling done here, code omitted
Resume Exit_
End Sub
'-------------
' Class DAOExt
'-------------
' append to recordset from Dictionary, return autonumber id of new record
Public Function appendFromHash(rst As DAO.Recordset, _
rec As Dictionary, _
Optional map As Dictionary, _
Optional wrk As DAO.workspace) As Long
Dim flds() As Variant, vals() As Variant, ifld As Long, k As Variant
Dim f As DAO.Field, rst_id As DAO.Recordset
Dim isInTrans As Boolean, isPersistWrk As Boolean
On Error GoTo Err_
' set up map (code omitted here)
For Each k In rec.Keys
If Not map.Exists(CStr(k)) Then _
Err.Raise 3265, "appendFromHash", "No field mapping found for [" & CStr(k) & "]"
flds(ifld) = map(CStr(k))
vals(ifld) = rec(CStr(k))
ifld = ifld + 1
Next k
If wrk Is Nothing Then
isPersistWrk = False
Set wrk = DBEngine(0)
End If
wrk.BeginTrans
isInTrans = True
rst.AddNew
With rst
For ifld = 0 To UBound(flds)
.Fields(flds(ifld)).Value = vals(ifld)
Next ifld
End With
rst.Update
Set rst_id = wrk(0).OpenRecordset("SELECT @@Identity", DAO.dbOpenForwardOnly, DAO.dbReadOnly)
appendFromHash = rst_id.Fields(0).Value
wrk.CommitTrans
isInTrans = False
Exit_:
On Error GoTo 0
If isInTrans And Not wrk Is Nothing Then wrk.Rollback
If Not isPersistWrk Then Set wrk = Nothing
Exit Function
Err_:
' runtime error handling, code omitted here
Resume Exit_
End Function
'-----------------
' Class DAOSession (the part that deals with the workspace and dbase connections)
'-----------------
Private wrk_ As DAO.workspace
Private connects_ As New Dictionary
Private dbs_ As New Dictionary
Public Property Get workspace() As DAO.workspace
If wrk_ Is Nothing Then
If DBEngine.Workspaces.Count > 0 Then
Set wrk_ = DBEngine(0)
End If
End If
Set workspace = wrk_
End Property
Public Property Get connectionTo(dbname As String) As DAO.database
connectTo dbname
Set connectionTo = connects_(dbname)
End Property
Public Sub connectTo(dbname As String)
Dim Cancel As Integer
Dim cnn As DAO.database
Dim opts As Dictionary
Cancel = False
' if already connected, use cached reference
If connects_.Exists(dbname) Then GoTo Exit_
If wrk_ Is Nothing Then _
Set wrk_ = DBEngine(0)
' note opts is a dictionary of connection options, code omitted here
Set cnn = wrk_.OpenDatabase(dbs_(dbname), _
CInt(opts("DAO.OPTIONS")), _
CBool(opts("DAO.READONLY")), _
CStr(opts("DAO.CONNECT")))
' Cache reference to dbase connection
connects_.Add dbname, cnn
Exit_:
Set cnn = Nothing
Exit Sub
End Sub