CODEWITHSUNDEEP
c#asp.netlucene.netepiserver
Bjarte Aune Olsen
Bjarte Aune Olsen

Reputation: 3310

Lucene.net - How do I create a negative query, ie. search for objects NOT containing something

I'm working on an EPiServer website using a Lucene.net based search engine.

I have a query for finding only pages with a certain pageTypeId. Now I want to do the opposite, I want to only find pages that is NOT a certain pageTypeId. Is that possible?

This is the code for creating a query to search only for pages with pageTypeId 1, 2 or 3:

public BooleanClause GetClause()
{
    var booleanQuery = new BooleanQuery();
    var typeIds = new List<string>();
    typeIds.Add("1");
    typeIds.Add("2");
    typeIds.Add("3");

    foreach (var id in this.typeIds)
    {
        var termQuery = new TermQuery(
            new Term(IndexFieldNames.PageTypeId, id));
        var clause = new BooleanClause(termQuery, 
            BooleanClause.Occur.SHOULD);
        booleanQuery.Add(clause);
    }
    return new BooleanClause(booleanQuery, 
        BooleanClause.Occur.MUST);
}

I want instead to create a query where I search for pages that have a pageTypeId that is NOT "4".

I tried simply replacing "SHOULD" and "MUST" with "MUST_NOT", but that didn't work.

Thanks to @goalie7960 for replying so quickly. Here is my revised code for searching for anything except some selected page types. This search includes all documents except those with pageTypeId "1", "2" or "3":

public BooleanClause GetClause()  
{
    var booleanQuery = new BooleanQuery();  
    booleanQuery.Add(new MatchAllDocsQuery(), 
        BooleanClause.Occur.MUST);

    var typeIds = new List<string>();  
    typeIds.Add("1");  
    typeIds.Add("2");  
    typeIds.Add("3");  

    foreach (var typeId in this.typeIds)  
    {
        booleanQuery.Add(new TermQuery(
            new Term(IndexFieldNames.PageTypeId, typeId)), 
            BooleanClause.Occur.MUST_NOT);
    }  
    return new BooleanClause(booleanQuery, 
        BooleanClause.Occur.MUST);  
}

Upvotes: 3

Views: 2012

Answers (1)

goalie7960
goalie7960

Reputation: 873

Assuming all your docs have a pageTypeId you can try using a MatchAllDocsQuery and then a MUST_NOT to remove all the docs you want to skip. Something like this would work I think:

BooleanQuery subQuery = new BooleanQuery();
subQuery.Add(new MatchAllDocsQuery(), BooleanClause.Occur.MUST);
subQuery.Add(new TermQuery(new Term(IndexFieldNames.PageTypeId, "4")), BooleanClause.Occur.MUST_NOT);
return subQuery;

Upvotes: 5

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