setTermInfosIndexDivisor problem in IndexReader with Lucene 3.0.2

I am upgrading lucene 2.4.1 to 3.0.2 in my java web project, in I开发者_JS百科ndexReader Lucene 2.4.1 has method setTermInfosIndexDivisor but in Lucene 3.0.2 we have to set it on opening an IndexReader

my question is how we can set TermInfosIndexDivisor if i don't have indexDeletionPolicy?? because when opening an IndexReader if you want to set TermInfosIndexDivisor then you also have to pass indexDeletionPolicy in Lucene 3.0.2

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A guess, but passing null will make it default to a KeepOnlyLastCommitDeletionPolicy. At least, that's how it works in 2.9.