TABLE OF CONTENTS
- 1. Query string syntax
- 2. Field names
- 5. Fuzzinesse
- 6. Proximity searches
- 7. Ranges
- 8. Boosting
- 9. Boolean operators
- 10. Grouping
- 11. Reserved characters
1. Query string syntax
The query string “mini-language” is used by the Query String Query and by the q query string parameter in the search API.
The query string is parsed into a series of terms and operators. A term can be a single word — quick or brown — or a phrase, surrounded by double quotes — "quick brown" — which searches for all the words in the phrase, in the same order.
Operators allow you to customize the search — the available options are explained below.
2. Field names
As mentioned in Query String Query, the default_field is searched for the search terms, but it is possible to specify other fields in the query syntax:
where the status field contains active
status:activewhere the title field contains quick or brown. If you omit the OR operator the default operator will be used
title:(quick OR brown)
title:(quick brown
where the author field contains the exact phrase "john smith"
author:"John Smith"where any of the fields book.title, book.content or book.date contains quick or brown(note how we need to escape the * with a backslash):
book.\*:(quick brown)where the field title has any non-null value:
where the status field contains active
where the title field contains quick or brown. If you omit the OR operator the default operator will be used
where the author field contains the exact phrase "john smith"
where any of the fields book.title, book.content or book.date contains quick or brown(note how we need to escape the * with a backslash):
where the field title has any non-null value:
_exists_:title5. Fuzzinesse
We can search for terms that are similar to, but not exactly like our search terms, using the “fuzzy” operator:
quikc~ brwn~ foks~This uses the Damerau-Levenshtein distance to find all terms with a maximum of two changes, where a change is the insertion, deletion or substitution of a single character, or transposition of two adjacent characters.
The default edit distance is 2, but an edit distance of 1 should be sufficient to catch 80% of all human misspellings. It can be specified as:
quikc~16. Proximity searches
While a phrase query (eg "john smith") expects all of the terms in exactly the same order, a proximity query allows the specified words to be further apart or in a different order. In the same way that fuzzy queries can specify a maximum edit distance for characters in a word, a proximity search allows us to specify a maximum edit distance of words in a phrase: "fox quick"~5
The closer the text in a field is to the original order specified in the query string, the more relevant that document is considered to be. When compared to the above example query, the phrase "quick fox" would be considered more relevant than "quick brown fox".
7. Ranges
Ranges can be specified for date, numeric or string fields. Inclusive ranges are specified with square brackets [min TO max] and exclusive ranges with curly brackets {min TO max}.
All days in 2012:
date:[2012-01-01 TO 2012-12-31]Numbers 1..5
count:[1 TO 5]Tags between alpha and omega, excluding alpha and omega:
tag:{alpha TO omega}Numbers from 10 upwards
count:[10 TO *]Dates before 2012
date:{* TO 2012-01-01}
Curly and square brackets can be combined:
Numbers from 1 up to but not including 5
count:[1 TO 5}
Ranges with one side unbounded can use the following syntax:
age:>10
age:>=10
age:<10
age:<=10Note To combine an upper and lower bound with the simplified syntax, you would need to join two clauses with an AND operator:
age:(>=10 AND <20)
age:(+>=10 +<20)The parsing of ranges in query strings can be complex and error prone. It is much more reliable to use an explicit range query.
8. Boosting
Use the boost operator ^ to make one term more relevant than another. For instance, if we want to find all documents about foxes, but we are especially interested in quick foxes:
quick^2 foxThe default boost value is 1, but can be any positive floating point number. Boosts between 0 and 1 reduce relevance. Boosts can also be applied to phrases or to groups:
"john smith"^2 (foo bar)^49. Boolean operators
By default, all terms are optional, as long as one term matches. A search for foo bar baz will find any document that contains one or more of foo or bar or baz. We have already discussed the default_operator above which allows you to force all terms to be required, but there are also boolean operators which can be used in the query string itself to provide more control.
The preferred operators are + (this term must be present) and - (this term must not be present). All other terms are optional. For example, this query:
quick brown +fox -newsstates that:
fox must be present
news must not be present
quick and brown are optional — their presence increases the relevance The familiar operators AND, OR and NOT (also written &&, || and !) are also supported. However, the effects of these operators can be more complicated than is obvious at first glance. NOT takes precedence over AND, which takes precedence over OR. While the + and - only affect the term to the right of the operator, AND and OR can affect the terms to the left and right.
Rewriting the above query using AND, OR and NOT demonstrates the complexity:
quick OR brown AND fox AND NOT newsThis is incorrect, because brown is now a required term.
(quick OR brown) AND fox AND NOT newsThis is incorrect because at least one of quick or brown is now required and the search for those terms would be scored differently from the original query.
((quick AND fox) OR (brown AND fox) OR fox) AND NOT newsThis form now replicates the logic from the original query correctly, but the relevance scoring bears little resemblance to the original.
n contrast, the same query rewritten using the match query would look like this:
10. Grouping
Multiple terms or clauses can be grouped together with parentheses, to form sub-queries:
(quick OR brown) AND foxGroups can be used to target a particular field, or to boost the result of a sub-query:
status:(active OR pending) title:(full text search)^211. Reserved characters
If you need to use any of the characters which function as operators in your query itself (and not as operators), then you should escape them with a leading backslash. For instance, to search for (1+1)=2, you would need to write your query as \(1\+1\)\=2.
The reserved characters are: + - = && || > < ! ( ) { } [ ] ^ " ~ * ? : \ /
Failing to escape these special characters correctly could lead to a syntax error which prevents your query from running.
Note < and > can’t be escaped at all. The only way to prevent them from attempting to create a range query is to remove them from the query string entirely.