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/** @file multiandpostlist.cc
* @brief N-way AND postlist
*/
/* Copyright (C) 2007,2009,2011,2012,2015,2017 Olly Betts
* Copyright (C) 2009 Lemur Consulting Ltd
*
* 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 "multiandpostlist.h"
#include "omassert.h"
#include "debuglog.h"
using namespace std;
void
MultiAndPostList::allocate_plist_and_max_wt()
{
plist = new PostList * [n_kids];
try {
max_wt = new double [n_kids]();
} catch (...) {
delete [] plist;
plist = NULL;
throw;
}
}
MultiAndPostList::~MultiAndPostList()
{
if (plist) {
for (size_t i = 0; i < n_kids; ++i) {
delete plist[i];
}
delete [] plist;
}
delete [] max_wt;
}
Xapian::doccount
MultiAndPostList::get_termfreq_min() const
{
// The number of matching documents is minimised when we have the minimum
// number of matching documents from each sub-postlist, and these are
// maximally disjoint.
Xapian::doccount sum = plist[0]->get_termfreq_min();
if (sum) {
for (size_t i = 1; i < n_kids; ++i) {
Xapian::doccount sum_old = sum;
sum += plist[i]->get_termfreq_min();
// If sum < sum_old, the calculation overflowed and the true sum
// must be > db_size. Since we added a value <= db_size,
// subtracting db_size must un-overflow us.
if (sum >= sum_old && sum <= db_size) {
// It's possible there's no overlap.
return 0;
}
sum -= db_size;
}
AssertRelParanoid(sum,<=,MultiAndPostList::get_termfreq_est());
}
return sum;
}
Xapian::doccount
MultiAndPostList::get_termfreq_max() const
{
// We can't match more documents than the least of our sub-postlists.
Xapian::doccount result = plist[0]->get_termfreq_max();
for (size_t i = 1; i < n_kids; ++i) {
Xapian::doccount tf = plist[i]->get_termfreq_max();
if (tf < result) result = tf;
}
return result;
}
Xapian::doccount
MultiAndPostList::get_termfreq_est() const
{
LOGCALL(MATCH, Xapian::doccount, "MultiAndPostList::get_termfreq_est", NO_ARGS);
if (rare(db_size == 0))
RETURN(0);
// We calculate the estimate assuming independence. With this assumption,
// the estimate is the product of the estimates for the sub-postlists
// divided by db_size (n_kids - 1) times.
double result = plist[0]->get_termfreq_est();
for (size_t i = 1; i < n_kids; ++i) {
result = (result * plist[i]->get_termfreq_est()) / db_size;
}
return static_cast<Xapian::doccount>(result + 0.5);
}
TermFreqs
MultiAndPostList::get_termfreq_est_using_stats(
const Xapian::Weight::Internal & stats) const
{
LOGCALL(MATCH, TermFreqs, "MultiAndPostList::get_termfreq_est_using_stats", stats);
// We calculate the estimate assuming independence. With this assumption,
// the estimate is the product of the estimates for the sub-postlists
// divided by db_size (n_kids - 1) times.
TermFreqs freqs(plist[0]->get_termfreq_est_using_stats(stats));
double freqest = double(freqs.termfreq);
double relfreqest = double(freqs.reltermfreq);
double collfreqest = double(freqs.collfreq);
// Our caller should have ensured this.
Assert(stats.collection_size);
for (size_t i = 1; i < n_kids; ++i) {
freqs = plist[i]->get_termfreq_est_using_stats(stats);
// If the collection is empty, freqest should be 0 already, so leave
// it alone.
freqest = (freqest * freqs.termfreq) / stats.collection_size;
collfreqest = (collfreqest * freqs.collfreq) / stats.total_term_count;
// If the rset is empty, relfreqest should be 0 already, so leave
// it alone.
if (stats.rset_size != 0)
relfreqest = (relfreqest * freqs.reltermfreq) / stats.rset_size;
}
RETURN(TermFreqs(static_cast<Xapian::doccount>(freqest + 0.5),
static_cast<Xapian::doccount>(relfreqest + 0.5),
static_cast<Xapian::termcount>(collfreqest + 0.5)));
}
double
MultiAndPostList::get_maxweight() const
{
return max_total;
}
Xapian::docid
MultiAndPostList::get_docid() const
{
return did;
}
Xapian::termcount
MultiAndPostList::get_doclength() const
{
Assert(did);
Xapian::termcount doclength = plist[0]->get_doclength();
for (size_t i = 1; i < n_kids; ++i) {
AssertEq(doclength, plist[i]->get_doclength());
}
return doclength;
}
Xapian::termcount
MultiAndPostList::get_unique_terms() const
{
Assert(did);
Xapian::termcount unique_terms = plist[0]->get_unique_terms();
for (size_t i = 1; i < n_kids; ++i) {
AssertEq(unique_terms, plist[i]->get_unique_terms());
}
return unique_terms;
}
double
MultiAndPostList::get_weight() const
{
Assert(did);
double result = 0;
for (size_t i = 0; i < n_kids; ++i) {
result += plist[i]->get_weight();
}
return result;
}
bool
MultiAndPostList::at_end() const
{
return (did == 0);
}
double
MultiAndPostList::recalc_maxweight()
{
max_total = 0.0;
for (size_t i = 0; i < n_kids; ++i) {
double new_max = plist[i]->recalc_maxweight();
max_wt[i] = new_max;
max_total += new_max;
}
return max_total;
}
PostList *
MultiAndPostList::find_next_match(double w_min)
{
advanced_plist0:
if (plist[0]->at_end()) {
did = 0;
return NULL;
}
did = plist[0]->get_docid();
for (size_t i = 1; i < n_kids; ++i) {
bool valid;
check_helper(i, did, w_min, valid);
if (!valid) {
next_helper(0, w_min);
goto advanced_plist0;
}
if (plist[i]->at_end()) {
did = 0;
return NULL;
}
Xapian::docid new_did = plist[i]->get_docid();
if (new_did != did) {
skip_to_helper(0, new_did, w_min);
goto advanced_plist0;
}
}
return NULL;
}
PostList *
MultiAndPostList::next(double w_min)
{
next_helper(0, w_min);
return find_next_match(w_min);
}
PostList *
MultiAndPostList::skip_to(Xapian::docid did_min, double w_min)
{
skip_to_helper(0, did_min, w_min);
return find_next_match(w_min);
}
std::string
MultiAndPostList::get_description() const
{
string desc("(");
desc += plist[0]->get_description();
for (size_t i = 1; i < n_kids; ++i) {
desc += " AND ";
desc += plist[i]->get_description();
}
desc += ')';
return desc;
}
Xapian::termcount
MultiAndPostList::get_wdf() const
{
Xapian::termcount totwdf = 0;
for (size_t i = 0; i < n_kids; ++i) {
totwdf += plist[i]->get_wdf();
}
return totwdf;
}
Xapian::termcount
MultiAndPostList::count_matching_subqs() const
{
Xapian::termcount total = 0;
for (size_t i = 0; i < n_kids; ++i) {
total += plist[i]->count_matching_subqs();
}
return total;
}
void
MultiAndPostList::gather_position_lists(OrPositionList* orposlist)
{
for (size_t i = 0; i < n_kids; ++i) {
plist[i]->gather_position_lists(orposlist);
}
}
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