Searching a substring using solr

Question

I am trying to move my code from Lucene to Solr, but am facing an issue. I have 4 fields indexed, all the field are of text_general type (from the managed schema). The code from Lucene is:

filterSearchText = filterSearchText.Or(x => x.LastName.Contains(searchRequest.Keyword));
filterSearchText = filterSearchText.Or(x => x.Content.Contains(searchRequest.Keyword));
filterSearchText = filterSearchText.Or(x => x.RelatedContent.Contains(searchRequest.Keyword));
filterSearchText = filterSearchText.Or(x => x.SearchKeywords.Contains(searchRequest.Keyword));

So whenever I search a single word (e.g. "health") Solr gives the same results as Lucene, but when I search multiple words (e.g. "health ser") it does not give any result. The query is in the logs as follows for single and multiple words:

last_name_t:(*health*) OR _content:(*health*) OR relatedcontent_s:(*health*) OR search_keywords_t:(*health*)

and for multiple words

last_name_t:("\*health ins\*") OR _content:("\*health ins\*") OR relatedcontent_s:("\*health ins\*") OR search_keywords_t:("\*health ins\*")

but when I search for the full keywords such as (e.g. "health services") I get correct results with the query:

last_name_t:("\*Health Services\*") OR _content:("\*Health Services\*") OR relatedcontent_s:("\*Health Services\*") OR search_keywords_t:("\*Health Services\*")

So what is the replacement for finding the substring in Solr?

Answer 1

I faced the same issue, then I replaced

contains

with

MatchWildcard

and it worked fined for me. Update your code syntax as below:

filterSearchText = filterSearchText.Or(x => x.LastName.MatchWildcard(searchRequest.Keyword));

Answer 2

I have faced with the same issue some time ago. As it is mentioned in documentation, Solr does not support the wildcard (say partial) query for search phrases (this is a type of query to which .Contains("simple site") will be converted):

Solr’s standard query parser supports single and multiple character wildcard searches within single terms. Wildcard characters can be applied to single terms, but not to search phrases. https://lucene.apache.org/solr/guide/6_6/the-standard-query-parser.html

When you try to search health, your query is parsed as <str name="parsed query">content:health </str> and Solr searches for health as a part of word or an entire word and it works fine. But when you try to search health ins, your query is parsed as <str name="parsedquery">PhraseQuery(_content:"health ins") </str>. In this case, Solr searches of containing the health and ins just as entire words in the document and you don't get any results, because you don't have a document with ins word in the content.

The easiest way to supporting multi word search with search by the part of word is to apply the code like below:

using (var searchContext = ContentSearchManager.GetIndex(new SitecoreIndexableItem(startItem)).CreateSearchContext()) 
{

var querySplitted = queryItem.Split(' '); //Split the queryItem by the white space (or any other symbols if you need) 

var predicate = PredicateBuilder.True <TIndexModel>(); 

foreach (var query in querySplitted) 
{ 
    predicate  = predicate.And(item => item.Content.Contains(query)); 
} 

var query = searchContext.GetQueryable<SearchResultItem>().Filter(predicate);
}

The code above works as expect.

Another way is to change the tokenizer. But in case you decide to change the analyzer, be careful as the size of index will increase and potentially can cause a performance issue. Make sure you know what you're doing before changing of analyzer.

I have explained how the analyzer changing might help you with the issue in the following article: https://www.brimit.com/blog/sitecore-multiple-partial-word-search-solr