Terms¶

A query is broken up into terms and operators. There are two types of terms: single terms and phrases.

A single term is a single word such as “test” or “hello”.

A phrase is a group of words surrounded by double quotes such as “hello world”.

Multiple terms can be combined together with Boolean operators to form a more complex query (see below).

Fields¶

When performing a search, you can either specify the default field.

As an example, let us assume a Lucene index contains text as the default field. If you want to find the document entitled “Jakarta Project”, which contains the text “lucene”, you can enter:

text:lucene

or

lucene

Since text is the default field, the field indicator is not required.

Term Modifiers¶

Lucene supports modifying query terms to provide a wide range of searching options.

• Wildcard Searches Lucene supports single and multiple character wildcard searches.

  To perform a single character wildcard search, use the ? symbol.

  To perform a multiple character wildcard search, use the * symbol.

  The single character wildcard search looks for terms that match that with the single character replaced. For example, to search for “text” or “test” you can use the search:

  te?t
  

  Multiple character wildcard searches look for 0 or more characters. For example, to search for “test”, “tests” or “tester” you can use the search:

  test*
  

  You can also use the wildcard searches in the middle of a term.

  te*t
  

  Note

  You cannot use a * or ? symbol as the first character of a search.

• Fuzzy Searches

  Lucene supports fuzzy searches based on the Levenshtein Distance or Edit Distance algorithm. To do a fuzzy search use the tilde (swung dash), ~, symbol at the end of a single word Term. For example, to search for a term similar in spelling to “roam” use the fuzzy search:

  roam~
  

  This search will find terms like foam and roams.

  An additional (optional) parameter can specify the required similarity. The value is between 0 and 1, with a value closer to 1 only terms with a higher similarity will be matched. For example:

  roam~0.8
  

  The default that is used, if the parameter is not given, is 0.5.

• Proximity Searches

  Lucene supports finding words that are within a specific distance away. To do a proximity search, use the tilde, ~, symbol at the end of a phrase. For example, to search for “apache” and “jakarta” within 10 words of each other in a document use the search:

  "jakarta apache"~10
  

• Range Searches

  Range Queries allow one to match documents whose field(s) values are between the lower and upper bound specified by the Range Query. Range Queries can be inclusive or exclusive of the upper and lower bounds. Sorting is done lexicographically.

  mod_date:[20020101 TO 20030101]
  

  This will find documents whose mod_date fields have values between 20020101 and 20030101, inclusive. Note that Range Queries are not reserved for date fields. You could also use range queries with non-date fields:

  title:{Aida TO Carmen}
  

  This will find all documents whose titles are between “Aida” and “Carmen”, but not including “Aida” and “Carmen”.

  Inclusive range queries are denoted by square brackets. Exclusive range queries are denoted by curly brackets.

• Boosting a Term

  Lucene provides the relevance level of matching documents based on the terms found. To boost a term, use the caret, ^, symbol with a boost factor (a number) at the end of the term you are searching. The higher the boost factor, the more relevant the term will be.

  Boosting allows you to control the relevance of a document by boosting its term. For example, if you are searching for

  jakarta apache
  

  and you want the term “jakarta” to be more relevant, boost it using the ^ symbol along with the boost factor next to the term. You would type:

  jakarta^4 apache
  

  This will make documents with the term jakarta appear more relevant. You can also boost Phrase Terms as in the example:

  "jakarta apache"^4 "jakarta lucene"
  

  By default, the boost factor is 1. Although the boost factor must be positive, it can be less than 1 (e.g. 0.2)

Boolean Operators¶

Boolean operators allow terms to be combined through logic operators. Lucene supports AND, +, OR, NOT and - as Boolean operators (Boolean operators must be ALL CAPS).

• OR

  The OR operator is the default conjunction operator. This means that if there is no Boolean operator between two terms, the OR operator is used. The OR operator links two terms and finds a matching document, if either of the terms exists in a document. This is equivalent to a union using sets. The symbol || can be used in place of the word OR.

  To search for documents that contain either “jakarta apache” or just “jakarta” use the query:

  "jakarta apache" jakarta
  

  or

  "jakarta apache" OR jakarta
  

• AND

  The AND operator matches documents, where both terms exist, anywhere in the text of a single document. This is equivalent to an intersection using sets. The symbol && can be used in place of the word AND.

  To search for documents that contain “jakarta apache” and “jakarta lucene” use the query:

  "jakarta apache" AND "jakarta lucene"
  

• +

  The ‘+’ or required operator requires that the term after the ‘+’ symbol exist somewhere in the field of a single document.

  To search for documents that must contain “jakarta” and may contain “lucene” use the query:

  +jakarta apache
  

• NOT

  The NOT operator excludes documents that contain the term after NOT. This is equivalent to a difference using sets. The symbol ! can be used in place of the word NOT.

  To search for documents that contain “jakarta apache” but not “jakarta lucene” use the query:

  "jakarta apache" NOT "jakarta lucene"
  

  Note

  The NOT operator cannot be used with just one term. For example, the following search will return no results:

  NOT "jakarta apache"
  

• -

  The ‘-‘ or prohibit operator excludes documents that contain the term after the - symbol.

  To search for documents that contain “jakarta apache” but not “jakarta lucene” use the query:

  "jakarta apache" -"jakarta lucene"
  

Grouping¶

Lucene supports using parentheses to group clauses to form subqueries. This can be very useful, if you want to control the Boolean logic for a query.

To search for either “jakarta” or “apache”, and “Web” use the query:

(jakarta OR apache) AND Web

This eliminates any confusion and makes you sure that “Web” must exist and either term “jakarta” or “apache” may exist.

Field Grouping¶

Lucene supports using parentheses to group multiple clauses to a single field.

To search for a title that contains both the word “return” and the phrase “pink panther” use the query:

title:(+return +"pink panther")

Escaping Special Characters¶

Lucene supports escaping special characters that are part of the query syntax. The current special characters list is

+ - && \|\| ! ( ) { } [ ] ^ " ~ \* ? : \\

To escape these characters, add \ before the character. For example, to search for (1+1):2 use the query:

\(1\+1\)\:2