On 2/2/2017 8:15 AM, Maciej Ł. PCSS wrote: > regardless of the value of such a use-case, there is another thing > that stays unknown for me. > > Does SOLR support a simple and silly 'exact substring match'? I mean, > is it possible to search for (actually filter by) a raw substring > without tokenization and without any kind of processing/simplifying > the searched information? By a 'raw substring' I mean a character > string that, among others, can contain non-letters (colons, brackets, > etc.) - basically everything the user is able to input via keyboard. > > Does this use case meet SOLR technical possibilities even if that > means a big efficiency cost?
Because you want to do substring matches, things are somewhat more complicated than if you wanted to do a full exact-string-only query. First I'll tackle the full exact query idea, because the info is also important for substrings: If the class in the fieldType is "solr.StrField" then the input will be indexed exactly as it is sent, all characters preserved, and all characters needing to be in the query. On the query side, you would need to escape any special characters in the query string -- spaces, colons, and several other characters. Escaping is done with the backslash. If you are manually constructing URL parameters for an HTTP request, you would also need to be aware of URL encoding. Some Solr libraries (like SolrJ) are capable of handling all the URL encoding for you. Matching *substrings* with StrField would involve either a regular expression query (with .* before and after) or a wildcard query, which Erick described in his reply. An alternate way to do substring matches is the NGram or EdgeNGram filters, and not using wildcards or regex. This method will increase your index size, possibly by a large amount. To use this method, you'd need to switch back to solr.TextField, use the keyword tokenizer, and then follow that with the appropriate NGram filter. Depending on your exact needs, you might only do the NGram filter on the index side, or you might need it on both index and query analysis. Escaping special characters on the query side would still be required. The full list of characters that require escaping is at the end of this page: http://lucene.apache.org/core/6_4_0/queryparser/org/apache/lucene/queryparser/classic/package-summary.html?is-external=true#Escaping_Special_Characters Note that it shows && and || as special characters, even though these are in fact two characters each. Typically even a single instance of these characters requires escaping. Solr will also need spaces to be escaped. Thanks, Shawn
