Difference between BooleanClause.Occur.Must and BooleanClause.Occur.SHOULD in lucene

boolean, lucene, search

Solution

`BooleanClause.Occur.SHOULD` means that the clause is optional, whereas `BooleanClause.Occur.Must` means that the clause is compulsory.

However, if a boolean query only has optional clauses, at least one clause must match for a document to appear in the results.

For better control over what documents match a BooleanQuery, there is also a minimumShouldMatch parameter which lets you tell Lucene that at least `minimumShouldMatch` `BooleanClause.Occur.SHOULD` clauses must match for a document to appear in the results.

Problem

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