#ifndef lint
static char rcsid[] = "@(#$Id: stemdb.cpp,v 1.1 2006-04-13 09:50:03 dockes Exp $ (C) 2005 J.F.Dockes";
#endif
#include <algorithm>
#include <map>
#include <xapian.h>
#include <xapian/stem.h>
#include "stemdb.h"
#include "wipedir.h"
#include "pathut.h"
#include "debuglog.h"
#include "smallut.h"
using namespace std;
namespace Rcl {
namespace StemDb {
const static string stemdirstem = "stem_";
/// Compute name of stem db for given base database and language
static string stemdbname(const string& dbdir, const string& lang)
{
return path_cat(dbdir, stemdirstem + lang);
}
list<string> getLangs(const string& dbdir)
{
string pattern = stemdirstem + "*";
list<string> dirs = path_dirglob(dbdir, pattern);
for (list<string>::iterator it = dirs.begin(); it != dirs.end(); it++) {
*it = path_basename(*it);
*it = it->substr(stemdirstem.length(), string::npos);
}
return dirs;
}
bool deleteDb(const string& dbdir, const string& lang)
{
string dir = stemdbname(dbdir, lang);
if (wipedir(dir) == 0 && rmdir(dir.c_str()) == 0)
return true;
return false;
}
// Autoclean/delete directory
class DirWiper {
public:
string dir;
bool do_it;
DirWiper(string d) : dir(d), do_it(true) {}
~DirWiper() {
if (do_it) {
wipedir(dir);
rmdir(dir.c_str());
}
}
};
// Deciding if we try to stem the term. If it has numerals or capitals
// we don't
inline static bool
p_notlowerascii(unsigned int c)
{
if (c < 'a' || (c > 'z' && c < 128))
return true;
return false;
}
/**
* Create database of stem to parents associations for a given language.
* We walk the list of all terms, stem them, and create another Xapian db
* with documents indexed by a single term (the stem), and with the list of
* parent terms in the document data.
*/
bool createDb(Xapian::Database& xdb, const string& dbdir, const string& lang)
{
LOGDEB(("StemDb::createDb(%s)\n", lang.c_str()));
// First build the in-memory stem database:
// We walk the list of all terms, and stem each.
// If the stem is identical to the term, no need to create an entry
// Else, we add an entry to the multimap.
// At the end, we only save stem-terms associations with several terms, the
// others are not useful
// Note: a map<string, list<string> > would probably be more efficient
multimap<string, string> assocs;
// Statistics
int nostem=0; // Dont even try: not-alphanum (incomplete for now)
int stemconst=0; // Stem == term
int stemdiff=0; // Count of all different stems
int stemmultiple = 0; // Count of stems with multiple derivatives
try {
Xapian::Stem stemmer(lang);
Xapian::TermIterator it;
for (it = xdb.allterms_begin();
it != xdb.allterms_end(); it++) {
// If it has any non-lowercase 7bit char, cant be stemmable
string::iterator sit = (*it).begin(), eit = sit + (*it).length();
if ((sit = find_if(sit, eit, p_notlowerascii)) != eit) {
++nostem;
// LOGDEB(("stemskipped: [%s], because of 0x%x\n",
// (*it).c_str(), *sit));
continue;
}
string stem = stemmer.stem_word(*it);
//cerr << "word " << *it << " stem " << stem << endl;
if (stem == *it) {
++stemconst;
continue;
}
assocs.insert(pair<string,string>(stem, *it));
}
} catch (const Xapian::Error &e) {
LOGERR(("Db::createStemDb: build failed: %s\n", e.get_msg().c_str()));
return false;
} catch (...) {
LOGERR(("Db::createStemDb: build failed: no stemmer for %s ? \n",
lang.c_str()));
return false;
}
// Create xapian database for stem relations
string stemdbdir = stemdbname(dbdir, lang);
// We want to get rid of the db dir in case of error. This gets disarmed
// just before success return.
DirWiper wiper(stemdbdir);
const char *ermsg = "NOERROR";
Xapian::WritableDatabase sdb;
try {
sdb = Xapian::WritableDatabase(stemdbdir,
Xapian::DB_CREATE_OR_OVERWRITE);
} catch (const Xapian::Error &e) {
ermsg = e.get_msg().c_str();
} catch (const string &s) {
ermsg = s.c_str();
} catch (const char *s) {
ermsg = s;
} catch (...) {
ermsg = "Caught unknown exception";
}
if (ermsg != "NOERROR") {
LOGERR(("Db::createstemdb: exception while opening [%s]: %s\n",
stemdbdir.c_str(), ermsg));
return false;
}
// Enter pseud-docs in db. Walk the multimap, only enter
// associations where there are several parent terms
string stem;
list<string> derivs;
for (multimap<string,string>::const_iterator it = assocs.begin();
it != assocs.end(); it++) {
if (stem == it->first) {
// Staying with same stem
derivs.push_back(it->second);
// cerr << " " << it->second << endl;
} else {
// Changing stems
++stemdiff;
if (derivs.size() == 1) {
// Exactly one term stems to this. Check for the case where
// the stem itself exists as a term. The code above would not
// have inserted anything in this case.
if (xdb.term_exists(stem))
derivs.push_back(stem);
}
if (derivs.size() > 1) {
// Previous stem has multiple derivatives. Enter in db
++stemmultiple;
Xapian::Document newdocument;
newdocument.add_term(stem);
// The doc data is just parents=blank-separated-list
string record = "parents=";
for (list<string>::const_iterator it = derivs.begin();
it != derivs.end(); it++) {
record += *it + " ";
}
record += "\n";
LOGDEB1(("stemdocument data: %s\n", record.c_str()));
newdocument.set_data(record);
try {
sdb.replace_document(stem, newdocument);
} catch (...) {
LOGERR(("Db::createstemdb: replace failed\n"));
return false;
}
}
derivs.clear();
stem = it->first;
derivs.push_back(it->second);
// cerr << "\n" << stem << " " << it->second;
}
}
LOGDEB(("Stem map size: %d stems %d mult %d no %d const %d\n",
assocs.size(), stemdiff, stemmultiple, nostem, stemconst));
wiper.do_it = false;
return true;
}
/**
* Expand term to list of all terms which stem to the same term.
*/
list<string> stemExpand(const string& dbdir, const string& lang,
const string& term)
{
list<string> explist;
try {
Xapian::Stem stemmer(lang);
string stem = stemmer.stem_word(term);
LOGDEB(("stemExpand: [%s] stem-> [%s]\n", term.c_str(), stem.c_str()));
// Try to fetch the doc from the stem db
string stemdbdir = stemdbname(dbdir, lang);
Xapian::Database sdb(stemdbdir);
LOGDEB1(("stemExpand: %s lastdocid: %d\n",
stemdbdir.c_str(), sdb.get_lastdocid()));
if (!sdb.term_exists(stem)) {
LOGDEB1(("Db::stemExpand: no term for %s\n", stem.c_str()));
explist.push_back(term);
return explist;
}
Xapian::PostingIterator did = sdb.postlist_begin(stem);
if (did == sdb.postlist_end(stem)) {
LOGDEB1(("stemExpand: no term(1) for %s\n",stem.c_str()));
explist.push_back(term);
return explist;
}
Xapian::Document doc = sdb.get_document(*did);
string data = doc.get_data();
// No need for a conftree, but we need to massage the data a little
string::size_type pos = data.find_first_of("=");
++pos;
string::size_type pos1 = data.find_last_of("\n");
if (pos == string::npos || pos1 == string::npos ||pos1 <= pos) { // ??
explist.push_back(term);
return explist;
}
stringToStrings(data.substr(pos, pos1-pos), explist);
if (find(explist.begin(), explist.end(), term) == explist.end()) {
explist.push_back(term);
}
LOGDEB(("stemExpand: %s -> %s\n", stem.c_str(),
stringlistdisp(explist).c_str()));
} catch (...) {
LOGERR(("stemExpand: error accessing stem db\n"));
explist.push_back(term);
return explist;
}
return explist;
}
}
}