1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
|
/** @file phrasepostlist.cc
* @brief Return docs containing terms forming a particular phrase.
*/
/* Copyright (C) 2006,2007,2009,2010,2011,2014,2015,2017 Olly Betts
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <config.h>
#include "phrasepostlist.h"
#include "debuglog.h"
#include "backends/positionlist.h"
#include "omassert.h"
#include "str.h"
#include <algorithm>
#include <vector>
using namespace std;
PhrasePostList::PhrasePostList(PostList *source_,
Xapian::termpos window_,
const vector<PostList*>::const_iterator &terms_begin,
const vector<PostList*>::const_iterator &terms_end)
: SelectPostList(source_), window(window_), terms(terms_begin, terms_end)
{
size_t n = terms.size();
Assert(n > 1);
poslists = new PositionList*[n];
}
PhrasePostList::~PhrasePostList()
{
delete [] poslists;
}
void
PhrasePostList::start_position_list(unsigned i)
{
poslists[i] = terms[i]->read_position_list();
}
bool
PhrasePostList::test_doc()
{
LOGCALL(MATCH, bool, "PhrasePostList::test_doc", NO_ARGS);
start_position_list(0);
poslists[0]->next();
if (poslists[0]->at_end()) RETURN(false);
unsigned read_hwm = 0;
do {
Xapian::termpos base = poslists[0]->get_position();
Xapian::termpos pos = base;
Xapian::termpos b;
unsigned i = 0;
do {
if (++i == terms.size()) RETURN(true);
if (i > read_hwm) {
read_hwm = i;
start_position_list(i);
}
poslists[i]->skip_to(pos + 1);
if (poslists[i]->at_end()) RETURN(false);
pos = poslists[i]->get_position();
b = pos + (terms.size() - i);
} while (b - base <= window);
// Advance the start of the window to the first position it could match
// in given the current position of term i.
poslists[0]->skip_to(b - window);
} while (!poslists[0]->at_end());
RETURN(false);
}
Xapian::termcount
PhrasePostList::get_wdf() const
{
// Calculate an estimate for the wdf of a phrase postlist.
//
// We use the minimum wdf of a sub-postlist as our estimate. See the
// comment in NearPostList::get_wdf() for justification of this estimate.
vector<PostList *>::const_iterator i = terms.begin();
Xapian::termcount wdf = (*i)->get_wdf();
while (++i != terms.end()) {
wdf = min(wdf, (*i)->get_wdf());
}
return wdf;
}
Xapian::doccount
PhrasePostList::get_termfreq_est() const
{
// It's hard to estimate how many times the phrase will occur as
// it depends a lot on the phrase, but usually the phrase will
// occur significantly less often than the individual terms.
return source->get_termfreq_est() / 3;
}
TermFreqs
PhrasePostList::get_termfreq_est_using_stats(
const Xapian::Weight::Internal & stats) const
{
LOGCALL(MATCH, TermFreqs, "PhrasePostList::get_termfreq_est_using_stats", stats);
// No idea how to estimate this - do the same as get_termfreq_est() for
// now.
TermFreqs result(source->get_termfreq_est_using_stats(stats));
result.termfreq /= 3;
result.reltermfreq /= 3;
RETURN(result);
}
string
PhrasePostList::get_description() const
{
string m = "(Phrase ";
m += str(window);
m += ' ';
m += source->get_description();
m += ")";
return m;
}
|
