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/** @file multi_alltermslist.cc
* @brief Class for merging AllTermsList objects from subdatabases.
*/
/* Copyright (C) 2007,2008,2009,2011 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 "multi_alltermslist.h"
#include <xapian/error.h>
#include "omassert.h"
#include <algorithm>
using namespace std;
using Xapian::Internal::intrusive_ptr;
/// Comparison functor which orders TermList* by ascending term name.
struct CompareTermListsByTerm {
/// Order by ascending term name.
bool operator()(const TermList *a, const TermList *b) const {
return a->get_termname() > b->get_termname();
}
};
template<class CLASS> struct delete_ptr {
void operator()(CLASS *p) const { delete p; }
};
MultiAllTermsList::MultiAllTermsList(const vector<intrusive_ptr<Xapian::Database::Internal> > & dbs,
const string & prefix)
{
// The 0 and 1 cases should be handled by our caller.
AssertRel(dbs.size(), >=, 2);
termlists.reserve(dbs.size());
try {
vector<intrusive_ptr<Xapian::Database::Internal> >::const_iterator i;
for (i = dbs.begin(); i != dbs.end(); ++i) {
termlists.push_back((*i)->open_allterms(prefix));
}
} catch (...) {
for_each(termlists.begin(), termlists.end(), delete_ptr<TermList>());
throw;
}
}
MultiAllTermsList::~MultiAllTermsList()
{
for_each(termlists.begin(), termlists.end(), delete_ptr<TermList>());
}
string
MultiAllTermsList::get_termname() const
{
return current_term;
}
Xapian::doccount
MultiAllTermsList::get_termfreq() const
{
if (termlists.empty()) return 0;
vector<TermList *>::const_iterator i = termlists.begin();
Xapian::doccount total_tf = (*i)->get_termfreq();
while (++i != termlists.end()) {
if ((*i)->get_termname() == current_term)
total_tf += (*i)->get_termfreq();
}
return total_tf;
}
Xapian::termcount
MultiAllTermsList::get_collection_freq() const
{
if (termlists.empty()) return 0;
vector<TermList *>::const_iterator i = termlists.begin();
Xapian::termcount total_cf = (*i)->get_collection_freq();
while (++i != termlists.end()) {
if ((*i)->get_termname() == current_term)
total_cf += (*i)->get_collection_freq();
}
return total_cf;
}
TermList *
MultiAllTermsList::next()
{
if (current_term.empty()) {
// Make termlists into a heap so that the one (or one of the ones) with
// earliest sorting term is at the top of the heap.
vector<TermList*>::iterator i = termlists.begin();
while (i != termlists.end()) {
(*i)->next();
if ((*i)->at_end()) {
delete *i;
i = termlists.erase(i);
} else {
++i;
}
}
make_heap(termlists.begin(), termlists.end(),
CompareTermListsByTerm());
} else {
// Advance to the next termname.
do {
TermList * tl = termlists.front();
pop_heap(termlists.begin(), termlists.end(),
CompareTermListsByTerm());
tl->next();
if (tl->at_end()) {
delete tl;
termlists.pop_back();
} else {
termlists.back() = tl;
push_heap(termlists.begin(), termlists.end(),
CompareTermListsByTerm());
}
} while (!termlists.empty() &&
termlists.front()->get_termname() == current_term);
}
if (termlists.size() <= 1) {
if (termlists.empty()) return NULL;
TermList * tl = termlists[0];
termlists.clear();
return tl;
}
current_term = termlists.front()->get_termname();
return NULL;
}
TermList *
MultiAllTermsList::skip_to(const std::string &term)
{
// Assume the skip is likely to be a long distance, and rebuild the heap
// from scratch. FIXME: It would be useful to profile this against an
// approach more like that next() uses if this ever gets heavy use.
vector<TermList*>::iterator i = termlists.begin();
while (i != termlists.end()) {
(*i)->skip_to(term);
if ((*i)->at_end()) {
delete *i;
i = termlists.erase(i);
} else {
++i;
}
}
if (termlists.size() <= 1) {
if (termlists.empty()) return NULL;
TermList * tl = termlists[0];
termlists.clear();
return tl;
}
make_heap(termlists.begin(), termlists.end(), CompareTermListsByTerm());
current_term = termlists.front()->get_termname();
return NULL;
}
bool
MultiAllTermsList::at_end() const
{
return termlists.empty();
}
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