Namespace Lucene.Net.QueryParsers.Simple

A simple query parser for human-entered queries.

Classes

SimpleQueryParser

SimpleQueryParser is used to parse human readable query syntax.

The main idea behind this parser is that a person should be able to type whatever they want to represent a query, and this parser will do its best to interpret what to search for no matter how poorly composed the request may be. Tokens are considered to be any of a term, phrase, or subquery for the operations described below. Whitespace including ' ' '\n' '\r' and '\t' and certain operators may be used to delimit tokens ( ) + | " .

Any errors in query syntax will be ignored and the parser will attempt to decipher what it can; however, this may mean odd or unexpected results.

Query Operators

  • '+' specifies AND operation: token1+token2
  • '|' specifies OR operation: token1|token2
  • '-' negates a single token: -token0
  • '"' creates phrases of terms: "term1 term2 ..."
  • '*' at the end of terms specifies prefix query: term*
  • '~N' at the end of terms specifies fuzzy query: term~1
  • '~N' at the end of phrases specifies near query: "term1 term2"~5
  • '(' and ')' specifies precedence: token1 + (token2 | token3)

The default operator is OR if no other operator is specified. For example, the following will ORtoken1 and token2 together: token1 token2

Normal operator precedence will be simple order from right to left. For example, the following will evaluate token1 OR token2 first, then AND with token3: 
token1 | token2 + token3

Escaping

An individual term may contain any possible character with certain characters requiring escaping using a '\'. The following characters will need to be escaped in terms and phrases: + | " ( ) ' \

The '-' operator is a special case. On individual terms (not phrases) the first character of a term that is - must be escaped; however, any '-' characters beyond the first character do not need to be escaped. For example:
  • -term1 -- Specifies NOT operation against term1
  • \-term1 -- Searches for the term -term1.
  • term-1 -- Searches for the term term-1.
  • term\-1 -- Searches for the term term-1.

The '*' operator is a special case. On individual terms (not phrases) the last character of a term that is '*' must be escaped; however, any '*' characters before the last character do not need to be escaped:
  • term1* -- Searches for the prefix term1
  • term1\* -- Searches for the term term1*
  • term*1 -- Searches for the term term*1
  • term\*1 -- Searches for the term term*1

Note that above examples consider the terms before text processing.

Enums

Operator

A simple query parser for human-entered queries.