Class: Ferret::Search::PrefixQuery

### Home Classes Methods

### In Files

- ext/r_search.c

### Parent

Ferret::Search::Query

### Methods

- ::new

### Files

- MIT-LICENSE
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- TUTORIAL

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# Ferret::Search::PrefixQuery

## Summary

A prefix query is like a TermQuery except that it matches any term with a specific prefix. PrefixQuery is expanded into a MultiTermQuery when submitted in a search.

## Example

PrefixQuery is very useful for matching a tree structure category hierarchy. For example, let's say you have the categories;

    "cat1/"
    "cat1/sub_cat1"
    "cat1/sub_cat2"
    "cat2"
    "cat2/sub_cat1"
    "cat2/sub_cat2"

Lets say you want to match everything in category 2. You'd build the query like this;

    query = PrefixQuery.new(:category, "cat2")
    # matches => "cat2"
    # matches => "cat2/sub_cat1"
    # matches => "cat2/sub_cat2"

### Public Class Methods

new(field, prefix, options = {}) → prefix-query click to toggle source

Create a new PrefixQuery to search for all terms with the prefix `prefix` in the field `field`. There is one option that you can set to change the behaviour of this query. `:max_terms` specifies the maximum number of terms to be added to the query when it is expanded into a MultiTermQuery. Let's say for example you search an index with a million terms for all terms beginning with the letter "s". You would end up with a very large query which would use a lot of memory and take a long time to get results, not to mention that it would probably match every document in the index. To prevent queries like this crashing your application you can set `:max_terms` which limits the number of terms that get added to the query. By default it is set to 512.

    static VALUE
    frb_prq_init(int argc, VALUE *argv, VALUE self)
    {
        return frb_mtq_init_specific(argc, argv, self, &prefixq_new);
    }

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