22.4. Query Language
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## 22.4. Query Language

Java Lucene and Zend_Search_Lucene provide quite powerful query language.

It mostly the same, but has some diffirences, which are mentioned below.

Full Java Lucene query language syntax documentation can be found here.

### 22.4.1. Terms

A query is broken up into terms and operators. There are three types of terms: Single Terms, Phrases, and Subqueries.

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 dolly".

A Subquery is a query surrounded by parentheses such as "(hello dolly)".

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

### 22.4.2. Fields

Lucene supports fielded data. When performing a search you can either specify a field, or use the default field. The field names depend on indexed data and default field is defined by current settings.

The first and major difference from Java Lucene is that terms are searched through all fields by default.

There are two static methods in Zend_Search_Lucene class, which allow to operate with this settengs:

    <?php
    $defaultSearchField = Zend_Search_Lucene::getDefaultSearchField();
    ...
    Zend_Search_Lucene::setDefaultSearchField('contents');
    ?>

`null` value means, that search is performed through all field. It's a default setting.

You can specify field by typing the field name followed by a colon ":" and then the term you are looking for.

As an example, let's assume a Lucene index contains two fields, title and text and text is the default field. If you want to find the document entitled "The Right Way" which contains the text "don't go this way", you can enter:

    title:"The Right Way" AND text:go

or

    title:"Do it right" AND go

If "text" is the default field, the field indicator is not required.

Note: The field is only valid for the term, phrase or subquery that it directly precedes, so the query

    title:Do it right

Will only find "Do" in the title field. It will find "it" and "right" in the default field, if default field is set, or in tha all indexed fields, if default field is set to `null`.

### 22.4.3. Term Modifiers

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

Zend_Search_Lucene supports "~" modifier only for phrases now [8]

### 22.4.4. Proximity Searches

Lucene supports finding words are a 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 a "Zend" and "Framework" within 10 words of each other in a document use the search:

    "Zend Framework"~10

### 22.4.5. Boosting a Term

Java Lucene and Zend_Search_Lucene provide 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

    PHP framework

and you want the term "PHP" to be more relevant boost it using the ^ symbol along with the boost factor next to the term. You would type:

    PHP^4 framework

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

    "PHP framework"^4 "Zend Framework"

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

### 22.4.6. Boolean Operators

Boolean operators allow terms to be combined through logic operators. Lucene supports AND, "+", OR, NOT and "-" as Boolean operators. Java Lucene needs boolean operators t obe ALL CAPS. Zend_Search_Lucene doesn't.

Boolean operators allow terms to be combined through logic operators. Lucene supports AND, "+", OR, NOT and "-" as Boolean operators.

AND, OR, and NOT operators and "+", "-" defines two styles to construct boolean queries. As opposed to Java Lucene Zend_Search_Lucene doesn't allow to mix these two styles.

If AND/OR/NOT style is used, then AND/OR operator must be present between all query terms. Each term may also be preceded by NOT operator. AND operator has higher precedence than OR. It differs from Java Lucene behavior.

#### 22.4.6.1. AND

The AND operator means, that all terms in "AND group" must match document.

To search for documents that contain "PHP framework" and "Zend Framework" use the query:

    "PHP framework" AND "Zend Framework"

#### 22.4.6.2. OR

The OR operator devides query into several optional parts.

To search for documents that contain "PHP framework" or "Zend Framework" use the query:

    "PHP framework" OR "Zend Framework"

#### 22.4.6.3. NOT

The NOT operator excludes documents that contain the term after NOT. But "AND group", which contains only terms with NOT operator, gives empty result instead of full set indexed documents.

To search for documents that contain "PHP framework" but not "Zend Framework" use the query:

    "PHP framework" AND NOT "Zend Framework"

#### 22.4.6.4. &&, ||, and ! operators

&&, ||, and ! may be used instead of AND, OR, and NOT operators.

#### 22.4.6.5. +

The "+" or required operator requires that the term after the "+" symbol must match the document.

To search for documents that must contain "Zend" and may contain "Framework" use the query:

    +Zend Framework

#### 22.4.6.6. -

The "-" or prohibit operator excludes documents that matches the term after the "-" symbol.

To search for documents that contain "PHP framework" but not "Zend Framework" use the query:

    "PHP framework" -"Zend Framework"

#### 22.4.6.7. no operator

If no operator is used, then behavior is defined by "default boolean operator".

It's `OR` by default.

That means, that term is optional. It may be or may not be presented within document, but documents with this term will have higher score.

To search for documents that requires "PHP framework" and may contain "Zend Framework" use the query:

    +"PHP framework" "Zend Framework"

Default boolean operator may be set or retrieved with `Zend_Search_Lucene_Search_QueryParser::setDefaultOperator($operator)` and `Zend_Search_Lucene_Search_QueryParser::getDefaultOperator()` methods.

These methods operate with `Zend_Search_Lucene_Search_QueryParser::B_AND` and `Zend_Search_Lucene_Search_QueryParser::B_OR` constants.

### 22.4.7. Grouping

Java Lucene and Zend_Search_Lucene support using parentheses to group clauses to form sub queries. This can be useful if you want to control the boolean logic for a query or mix different boolean query styles:

    +(framework OR library) +php

Zend_Search_Lucene supports subqueries of any level.

### 22.4.8. 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")

Zend_Search_Lucene supports subqueries of any level.

### 22.4.9. Escaping Special Characters

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

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

+ and - inside single terms are treated as common characters.

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

    \(1\+1\)\:2

[8] "~" for terms is used for fuzzy search, but fuzzy search queries are not supported yet.

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