Class: Ferret::Search::PhraseQuery

### Home Classes Methods

### In Files

- ext/r_search.c

### Parent

Ferret::Search::Query

### Methods

- ::new
- #<<
- #add_term
- #slop
- #slop=

### Files

- MIT-LICENSE
- README
- TODO
- TUTORIAL

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# Ferret::Search::PhraseQuery

## Summary

PhraseQuery matches phrases like "the quick brown fox". Most people are familiar with phrase queries having used them in most internet search engines.

### Slop

Ferret's phrase queries a slightly more advanced. You can match phrases with a slop, ie the match isn't exact but it is good enough. The slop is basically the word edit distance of the phrase. For example, "the quick brown fox" with a slop of 1 would match "the quick little brown fox". With a slop of 2 it would match "the brown quick fox".

    query = PhraseQuery.new(:content)
    query << "the" << "quick" << "brown" << "fox"

    # matches => "the quick brown fox"

    query.slop = 1
    # matches => "the quick little brown fox"
                               |__1__^

    query.slop = 2
    # matches => "the brown quick _____ fox"
                        ^_____2_____|

## Multi-PhraseQuery

Phrase queries can also have multiple terms in a single position. Let's say for example that we want to match synonyms for quick like "fast" and "speedy". You could the query like this;

    query = PhraseQuery.new(:content)
    query << "the" << ["quick", "fast", "speed"] << ["brown", "red"] << "fox"
    # matches => "the quick red fox"
    # matches => "the fast brown fox"

    query.slop = 1
    # matches => "the speedy little red fox"

You can also leave positions blank. Lets say you wanted to match "the quick <> fox" where "<>" could match anything (but not nothing). You'd build this query like this;

    query = PhraseQuery.new(:content)
    query.add_term("the").add_term("quick").add_term("fox", 2)
    # matches => "the quick yellow fox"
    # matches => "the quick alkgdhaskghaskjdh fox"

The second parameter to PhraseQuery#add_term is the position increment for the term. It is one by default meaning that every time you add a term it is expected to follow the previous term. But setting it to 2 or greater you are leaving empty spaces in the term.

There are also so tricks you can do by setting the position increment to

1. With a little help from your analyzer you can actually tag bold or

italic text for example. If you want more information about this, ask on the mailing list.

### Public Class Methods

new(field, slop = 0) → phrase_query click to toggle source

Create a new PhraseQuery on the field `field`. You need to add terms to the query it will do anything of value. See PhraseQuery#add_term.

    static VALUE
    frb_phq_init(int argc, VALUE *argv, VALUE self)
    {
        VALUE rfield, rslop;
        Query *q;
        rb_scan_args(argc, argv, "11", &rfield, &rslop);
        q = phq_new(frb_field(rfield));
        if (argc == 2) {
            ((PhraseQuery *)q)->slop = FIX2INT(rslop);
        }
        Frt_Wrap_Struct(self, NULL, &frb_q_free, q);
        object_add(q, self);
        return self;
    }

### Public Instance Methods

add_term(term, position_increment = 1) → phrase_query click to toggle source
phrase_query << term → phrase_query

Add a term to the phrase query. By default the position_increment is set to 1 so each term you add is expected to come directly after the previous term. By setting position_increment to 2 you are specifying that the term you just added should occur two terms after the previous term. For example;

    phrase_query.add_term("big").add_term("house", 2)
    # matches => "big brick house"
    # matches => "big red house"
    # doesn't match => "big house"

    static VALUE
    frb_phq_add(int argc, VALUE *argv, VALUE self)
    {
        VALUE rterm, rpos_inc;
        int pos_inc = 1;
        GET_Q();
        if (rb_scan_args(argc, argv, "11", &rterm, &rpos_inc) == 2) {
            pos_inc = FIX2INT(rpos_inc);
        }
        switch (TYPE(rterm)) {
            case T_STRING:
                {
                    phq_add_term(q, StringValuePtr(rterm), pos_inc);
                    break;
                }
            case T_ARRAY:
                {
                    int i;
                    char *t;
                    if (RARRAY_LEN(rterm) < 1) {
                        rb_raise(rb_eArgError, "Cannot add empty array to a "
                                 "PhraseQuery. You must add either a string or "
                                 "an array of strings");
                    }
                    t = StringValuePtr(RARRAY_PTR(rterm)[0]);
                    phq_add_term(q, t, pos_inc);
                    for (i = 1; i < RARRAY_LEN(rterm); i++) {
                        t = StringValuePtr(RARRAY_PTR(rterm)[i]);
                        phq_append_multi_term(q, t);
                    }
                    break;
                }
            default:
                rb_raise(rb_eArgError, "You can only add a string or an array of "
                         "strings to a PhraseQuery, not a %s\n",
                         rs2s(rb_obj_as_string(rterm)));
        }
        return self;
    }

add_term(term, position_increment = 1) → phrase_query click to toggle source
phrase_query << term → phrase_query

Add a term to the phrase query. By default the position_increment is set to 1 so each term you add is expected to come directly after the previous term. By setting position_increment to 2 you are specifying that the term you just added should occur two terms after the previous term. For example;

    phrase_query.add_term("big").add_term("house", 2)
    # matches => "big brick house"
    # matches => "big red house"
    # doesn't match => "big house"

    static VALUE
    frb_phq_add(int argc, VALUE *argv, VALUE self)
    {
        VALUE rterm, rpos_inc;
        int pos_inc = 1;
        GET_Q();
        if (rb_scan_args(argc, argv, "11", &rterm, &rpos_inc) == 2) {
            pos_inc = FIX2INT(rpos_inc);
        }
        switch (TYPE(rterm)) {
            case T_STRING:
                {
                    phq_add_term(q, StringValuePtr(rterm), pos_inc);
                    break;
                }
            case T_ARRAY:
                {
                    int i;
                    char *t;
                    if (RARRAY_LEN(rterm) < 1) {
                        rb_raise(rb_eArgError, "Cannot add empty array to a "
                                 "PhraseQuery. You must add either a string or "
                                 "an array of strings");
                    }
                    t = StringValuePtr(RARRAY_PTR(rterm)[0]);
                    phq_add_term(q, t, pos_inc);
                    for (i = 1; i < RARRAY_LEN(rterm); i++) {
                        t = StringValuePtr(RARRAY_PTR(rterm)[i]);
                        phq_append_multi_term(q, t);
                    }
                    break;
                }
            default:
                rb_raise(rb_eArgError, "You can only add a string or an array of "
                         "strings to a PhraseQuery, not a %s\n",
                         rs2s(rb_obj_as_string(rterm)));
        }
        return self;
    }

slop → integer click to toggle source

Return the slop set for this phrase query. See the PhraseQuery description for more information on slop

    static VALUE
    frb_phq_get_slop(VALUE self)
    {
        GET_Q();
        return INT2FIX(((PhraseQuery *)q)->slop);
    }

slop = slop → slop click to toggle source

Set the slop set for this phrase query. See the PhraseQuery description for more information on slop

    static VALUE
    frb_phq_set_slop(VALUE self, VALUE rslop)
    {
        GET_Q();
        ((PhraseQuery *)q)->slop = FIX2INT(rslop);
        return self;
    }

[Validate]

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