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stemdb.cpp    339 lines (302 with data), 10.3 kB

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#ifndef lint
static char rcsid[] = "@(#$Id: stemdb.cpp,v 1.12 2008-07-30 13:16:13 dockes Exp $ (C) 2005 J.F.Dockes";
#endif
/**
* Management of the auxiliary databases listing stems and their expansion
* terms
*/
#include <unistd.h>
#include <algorithm>
#include <map>
#include <xapian.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());
}
}
};
inline static bool
p_notlowerascii(unsigned int c)
{
if (c < 'a' || (c > 'z' && c < 128))
return true;
return false;
}
static bool addAssoc(Xapian::WritableDatabase &sdb, const string& stem,
const list<string>& derivs)
{
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";
LOGDEB2(("createStemDb: stmdoc data: [%s]\n", record.c_str()));
newdocument.set_data(record);
try {
sdb.replace_document(stem, newdocument);
} catch (...) {
LOGERR(("Db::createstemdb(addAssoc): replace failed\n"));
return false;
}
return true;
}
/**
* 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()));
Chrono cron;
// 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++) {
// Deciding if we try to stem the term. If it has any
// non-lowercase 7bit char (that is, numbers, capitals and
// punctuation) dont. We're still sending all multibyte
// utf-8 chars to the stemmer, which is not too well
// defined for xapian < 1.0, but seems to work anyway. We don't
// try to look for multibyte non alphabetic data.
string::iterator sit = (*it).begin(), eit = sit + (*it).length();
if ((sit = find_if(sit, eit, p_notlowerascii)) != eit) {
++nostem;
LOGDEB1(("stemskipped: [%s], because of 0x%x\n",
(*it).c_str(), *sit));
continue;
}
string stem = stemmer(*it);
LOGDEB2(("Db::createStemDb: word [%s], stem [%s]\n", (*it).c_str(),
stem.c_str()));
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;
}
LOGDEB1(("StemDb::createDb(%s): in memory map built: %.2f S\n",
lang.c_str(), cron.secs()));
// 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);
string ermsg;
Xapian::WritableDatabase sdb;
try {
sdb = Xapian::WritableDatabase(stemdbdir,
Xapian::DB_CREATE_OR_OVERWRITE);
} catch (const Xapian::Error &e) {
ermsg = e.get_msg();
} catch (const string &s) {
ermsg = s;
} catch (const char *s) {
ermsg = s;
} catch (...) {
ermsg = "Caught unknown exception";
}
if (!ermsg.empty()) {
LOGERR(("Db::createstemdb: exception while opening [%s]: %s\n",
stemdbdir.c_str(), ermsg.c_str()));
return false;
}
// Enter pseud-docs in db by walking the multimap.
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;
LOGDEB2(("createStemDb: stem [%s]\n", stem.c_str()));
// We need an entry even if there is only one derivative
// so that it is possible to search by entering the stem
// even if it doesnt exist as a term
if (!derivs.empty()) {
if (derivs.size() > 1)
++stemmultiple;
if (!addAssoc(sdb, stem, derivs)) {
return false;
}
derivs.clear();
}
stem = it->first;
derivs.push_back(it->second);
// cerr << "\n" << stem << " " << it->second;
}
}
if (!derivs.empty()) {
if (derivs.size() > 1)
++stemmultiple;
if (!addAssoc(sdb, stem, derivs)) {
return false;
}
}
LOGDEB1(("StemDb::createDb(%s): done: %.2f S\n",
lang.c_str(), cron.secs()));
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;
}
static string stringlistdisp(const list<string>& sl)
{
string s;
for (list<string>::const_iterator it = sl.begin(); it!= sl.end(); it++)
s += "[" + *it + "] ";
if (!s.empty())
s.erase(s.length()-1);
return s;
}
/**
* Expand term to list of all terms which stem to the same term, for one
* expansion language
*/
static bool stemExpandOne(const std::string& dbdir,
const std::string& lang,
const std::string& term,
list<string>& result)
{
try {
Xapian::Stem stemmer(lang);
string stem = stemmer(term);
LOGDEB(("stemExpand:%s: [%s] stem-> [%s]\n",
lang.c_str(), term.c_str(), stem.c_str()));
// Open stem database
string stemdbdir = stemdbname(dbdir, lang);
Xapian::Database sdb(stemdbdir);
LOGDEB0(("stemExpand: %s lastdocid: %d\n",
stemdbdir.c_str(), sdb.get_lastdocid()));
// Try to fetch the doc from the stem db
if (!sdb.term_exists(stem)) {
LOGDEB0(("Db::stemExpand: no term for %s\n", stem.c_str()));
} else {
Xapian::PostingIterator did = sdb.postlist_begin(stem);
if (did == sdb.postlist_end(stem)) {
LOGDEB0(("stemExpand: no term(1) for %s\n",stem.c_str()));
} else {
Xapian::Document doc = sdb.get_document(*did);
string data = doc.get_data();
// Build expansion list from database 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) {
// ??
} else {
stringToStrings(data.substr(pos, pos1-pos), result);
}
}
}
// If the user term or stem are not in the list, add them
if (find(result.begin(), result.end(), term) == result.end()) {
result.push_back(term);
}
if (find(result.begin(), result.end(), stem) == result.end()) {
result.push_back(stem);
}
LOGDEB0(("stemExpand:%s: %s -> %s\n", lang.c_str(), stem.c_str(),
stringlistdisp(result).c_str()));
} catch (...) {
LOGERR(("stemExpand: error accessing stem db. dbdir [%s] lang [%s]\n",
dbdir.c_str(), lang.c_str()));
result.push_back(term);
return false;
}
return true;
}
/**
* Expand term to list of all terms which stem to the same term, add the
* expansion sets for possibly multiple expansion languages
*/
bool stemExpand(const std::string& dbdir,
const std::string& langs,
const std::string& term,
list<string>& result)
{
list<string> llangs;
stringToStrings(langs, llangs);
for (list<string>::const_iterator it = llangs.begin();
it != llangs.end(); it++) {
list<string> oneexp;
stemExpandOne(dbdir, *it, term, oneexp);
result.insert(result.end(), oneexp.begin(), oneexp.end());
}
result.sort();
result.unique();
return true;
}
}
}