Access Violations while reading from /writing to sqLite

[ZeosDummy]

Hello,

we're currently having problems with our application (written in Delphi 2006) which uses Zeos 6.6.6 to implement a temporary data buffer in a sqLite file.
Generally the program works fine, except for some rare circumstances in which many (hundreds) consecutive Insert/Select queries are executed and an Access Violation occurs.
This happens irregularly; sometimes the app crashes at the 1000th query, sometimes earlier and sometimes it works without any errors (while processing the same data in all scenarios). Pressing the 'break' button we end up in Borland's GETMEM.INC which doesn't help much in finding the cause of the exception.
Some might think of multiple threads trying to read/write to the same connection / file at the same time, but that is not the case. It is a single thread having its own TZConnection and TZQuery objects accessing its 'own' file.

The call stacks basically show two different scenarios, both ending up in Zeos objects apparently causing the AV:

• while preparing to write to the DB

  Code: Select all

  :775642eb kernel32.RaiseException + 0x58
  System.SysGetMem(???)
  ZSqlStrings.TZSQLStrings.RebuildAll
  ZSqlStrings.TZSQLStrings.Changed
  Classes.TStringList.SetUpdateState(False)
  Classes.TStrings.EndUpdate
  Classes.TStrings.SetTextStr('INSERT INTO bla bla;')
  uGP_DS_MessageBuffer.TMessageBuffer.WriteRecord('Some more parameters, none of them empty or nil')
  uGP_DS_MessageBuffer.TMessageBuffer.InsertDataMessage('Some parameters, none of them empty or nil')
  uGP_DS_Main.TDSMain.wmWriteDataMessageToBuffer((33179, 75168960, 0, 0, 64704, 1146, 0, 0, 0, 0))
  uGP_DS_Main.TDSMain.WndProc((33179, 75168960, 0, 0, 64704, 1146, 0, 0, 0, 0))
  Classes.StdWndProc(788526,33179,75168960,0)
  uGP_DS_Main.TDSMain.ProcessMessages
  uGP_DS_Main.TDSMain.OnReadTimerTick($47ED428)
  (...)
  

• after reading from DB and processing the results

  Code: Select all

  :762442eb kernel32.RaiseException + 0x58
  :004048C8 System::NotifyNonDelphiException()
  :77339b6b ntdll.RtlRaiseStatus + 0x86
  System.SysGetMem(???)
  :773399f7 ntdll.KiUserExceptionDispatcher + 0xf
  Classes.TStream.ReadBuffer((no value),911)
  ZDbcResultSet.TZAbstractBlob.CreateWithStream($2851CF0)
  ZDbcSqLiteResultSet.TZSQLiteResultSet.GetBlob(5)
  ZDbcCachedResultSet.TZCachedResultSet.Fetch
  ZDbcCachedResultSet.TZCachedResultSet.FetchAll
  ZDbcCachedResultSet.TZCachedResultSet.Last
  ZDbcSqLiteStatement.TZSQLiteStatement.CreateResultSet('SELECT something something;'#$D#$A,$4A77518,7,$48AFED8,$28965C8)
  ZDbcSqLiteStatement.TZSQLiteStatement.ExecuteQuery('SELECT something something;'#$D#$A)
  ZDbcStatement.TZEmulatedPreparedStatement.ExecuteQuery('SELECT something something;'#$D#$A)
  ZDbcStatement.TZEmulatedPreparedStatement.ExecuteQueryPrepared
  ZAbstractRODataset.TZAbstractRODataset.CreateResultSet('SELECT something something'#$D#$A,-1)
  ZAbstractDataset.TZAbstractDataset.CreateResultSet('SELECT something something'#$D#$A,-1)
  ZAbstractRODataset.TZAbstractRODataset.InternalOpen
  DB.TDataSet.DoInternalOpen
  DB.TDataSet.OpenCursor(False)
  DB.TDataSet.SetActive(True)
  DB.TDataSet.Open
  uGP_DS_MessageBuffer.TMessageBuffer.ReadNextUnprocessedDataMessage(Some parameters none of them empty or nil)
  uGP_DS_Main.TDSMain.OnReadTimerTick($48AB740)
  (...)
  

I have spent hours trying to understand what is happening here, double checked my code to no avail. The fact that the problem is so unpredictable makes debugging quite impossible, as you never know if or when it happens. Especially as those queries work in most cases, the only differences being some different values to be inserted/read.
Has anyone an idea what the problem might be? Any hints greatly appreciated!

Cheers