Interesting Lucene.net Exception

Question

According to this or this, I used the same indexsearcher by multiple thread. But when I switched from FsDirectory to MMapDirectory, I got interesting exceptions. This work fine: ``` static void Main(string[] args) { DirectoryInfo directoryInfo = new DirectoryInfo(@"C:\Users\Tams\Desktop ew"); var directory = FSDirectory.Open(directoryInfo); var indexSearcher = new IndexSearcher(directory); const int times = 100; const int concurrentTaskCount = 5; var task = new Task[concurrentTaskCount]; for (int i = 0; i < concurrentTaskCount; i++) { task[i] = new Task(() => Search(indexSearcher, times)); task[i].Start(); } Task.WaitAll(task); } static void Search(IndexSearcher reader, int times) { List docs = new List(10000); for (int i = 0; i < times; i++) { var q = new TermQuery(new Term("title", "volume")); foreach (var scoreDoc in reader.Search(q, 100).ScoreDocs) { docs.Add(reader.Doc(scoreDoc.Doc)); } } } ``` But with this: ``` static void Main(string[] args) { DirectoryIn…

Accepted Answer

The source for MMapDirectory shows that this class does not use memory-mapped files, as expected. It loads all index files into memory using MemoryStream objects, and I would guess that those streams are the cause of the problem when different threads seeks and reads.

You can get a memory-based index by loading it into a RAMDirectory. This passes your test. (But it does what MMapDirectory currently does, not necessarily what you expect it to do...)

```
var fsDirectory = FSDirectory.Open(directoryInfo);
var directory = new RAMDirectory(fsDirectory);
```

Interesting Lucene.net Exception

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