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|
//
// parser.cc
//
// parser: Parses a boolean expression tree, retrieving and scoring
// the resulting document list
//
// Part of the ht://Dig package <http://www.htdig.org/>
// Copyright (c) 1995-2004 The ht://Dig Group
// For copyright details, see the file COPYING in your distribution
// or the GNU Library General Public License (LGPL) version 2 or later
// <http://www.gnu.org/copyleft/lgpl.html>
//
// $Id: parser.cc,v 1.36 2004/06/11 16:50:33 grdetil Exp $
//
#ifdef HAVE_CONFIG_H
#include "htconfig.h"
#endif /* HAVE_CONFIG_H */
#include "parser.h"
#include "HtPack.h"
#include "Collection.h"
#include "Dictionary.h"
#include "QuotedStringList.h"
#define WORD 1000
#define DONE 1001
QuotedStringList boolean_syntax_errors;
enum ErrorIndices { EXPECTED, SEARCH_WORD, AT_END, INSTEAD_OF, END_OF_EXPR, QUOTE };
//*****************************************************************************
Parser::Parser() :
words(*(HtConfiguration::config()))
{
tokens = 0;
result = 0;
current = 0;
valid = 1;
}
//*****************************************************************************
// int Parser::checkSyntax(List *tokenList)
// As the name of the function implies, we will only perform a syntax check
// on the list of tokens.
//
int
Parser::checkSyntax(List *tokenList)
{
HtConfiguration* config= HtConfiguration::config();
void reportError(char *);
// Load boolean_syntax_errors from configuration
// they should be placed in this order:
// 0 1 2 3 4
// Expected "a search word" "at the end" "instead of" "end of expression"
// 5
// "a closing quote"
boolean_syntax_errors.Destroy();
boolean_syntax_errors.Create(config->Find("boolean_syntax_errors"), "| \t\r\n\001");
if (boolean_syntax_errors.Count() == 5)
{ // for backward compatibility
boolean_syntax_errors.Add (new String ("a closing quote"));
if (debug)
cerr << "Parser::checkSyntax() : boolean_syntax_errors should have six entries\n";
} else if (boolean_syntax_errors.Count() != 6)
reportError("boolean_syntax_errors attribute should have six entries");
tokens = tokenList;
valid = 1;
fullexpr(0);
return valid;
}
//*****************************************************************************
/* Called by: Parser::parse(List*, ResultList&), checkSyntax(List*) */
/* Inputs: output -- if zero, simply check syntax */
/* otherwise, list matching documents in head of "stack" */
void
Parser::fullexpr(int output)
{
tokens->Start_Get();
lookahead = lexan();
expr(output);
if (valid && lookahead != DONE)
{
setError(boolean_syntax_errors[END_OF_EXPR]);
}
}
//*****************************************************************************
int
Parser::lexan()
{
current = (WeightWord *) tokens->Get_Next();
if (!current)
return DONE;
else if (mystrcasecmp((char*)current->word, "&") == 0)
return '&';
else if (mystrcasecmp((char*)current->word, "|") == 0)
return '|';
else if (mystrcasecmp((char*)current->word, "!") == 0)
return '!';
else if (mystrcasecmp((char*)current->word, "(") == 0)
return '(';
else if (mystrcasecmp((char*)current->word, ")") == 0)
return ')';
else if (mystrcasecmp((char*)current->word, "\"") == 0)
return '"';
else
return WORD;
}
//*****************************************************************************
// Attempt to deal with expressions in the form
// term | term | term ...
/* Called by: Parser::fullexpr(int), factor(int) */
/* Inputs: output -- if zero, simply check syntax */
void
Parser::expr(int output)
{
term(output);
while (1)
{
if (match('|'))
{
term(output);
if (output)
{
if(debug) cerr << "or--" << endl;
perform_or();
if(debug) cerr << "stack:" << stack.Size() << endl;
}
}
else
break;
}
if (valid && lookahead == WORD)
{
String expected = "'";
expected << boolean_keywords[AND] << "' "<< boolean_keywords[OR] <<" '"
<< boolean_keywords[OR] << "'";
setError(expected.get());
}
}
//*****************************************************************************
// Attempt to deal with terms in the form
// factor & factor & factor ...
/* Called by: Parser::expr(int) */
/* Inputs: output -- if zero, simply check syntax */
void
Parser::term(int output)
{
factor(output);
if(debug) cerr << "term:factor" << endl;
while (1)
{
if(match('&'))
{
factor(output);
if(output)
{
if(debug) cerr << "and--" << endl;
perform_and();
if(debug) cerr << "stack:" << stack.Size() << endl;
}
}
else if(match('!'))
{
factor(output);
if(output)
{
if(debug) cerr << "not--" << endl;
perform_not();
if(debug) cerr << "stack:" << stack.Size() << endl;
}
}
else
{
break;
}
}
}
//*****************************************************************************
/* Gather and score a (possibly bracketed) boolean expression */
/* Called by: Parser::term(int) */
/* Inputs: output -- if zero, simply check syntax */
void
Parser::factor(int output)
{
if(match('"'))
{
phrase(output);
}
else if (match('('))
{
expr(output);
if (match(')'))
{
return;
}
else
{
setError("')'");
}
}
else if (lookahead == WORD)
{
if (output)
{
perform_push();
}
lookahead = lexan();
}
else
{
setError(boolean_syntax_errors[SEARCH_WORD]);
// setError("a search word, a quoted phrase, a boolean expression between ()");
}
}
//*****************************************************************************
/* Gather and score a quoted phrase */
/* Called by: Parser::factor(int) */
/* Inputs: output -- if zero, simply check syntax */
void
Parser::phrase(int output)
{
List *wordList = 0;
double weight = 1.0;
while (1)
{
if (match('"'))
{
if (output)
{
if(!wordList) wordList = new List;
if(debug) cerr << "scoring phrase" << endl;
score(wordList, weight, FLAGS_MATCH_ONE); // look in all fields
}
break;
}
else if (lookahead == WORD)
{
weight *= current->weight;
if (output)
perform_phrase(wordList);
lookahead = lexan();
}
else if (lookahead == DONE)
{
setError(boolean_syntax_errors[QUOTE]);
break;
}
else
{
// skip '&' '|' and '!' in the phrase
current->isIgnore = 1;
if (output)
perform_phrase(wordList);
lookahead = lexan ();
}
} // end while
if(wordList) delete wordList;
}
//*****************************************************************************
int
Parser::match(int t)
{
if (lookahead == t)
{
lookahead = lexan();
return 1;
}
else
return 0;
}
//*****************************************************************************
void
Parser::setError(char *expected)
{
if (valid)
{
valid = 0;
error = 0;
error << boolean_syntax_errors[EXPECTED] << ' ' << expected;
if (lookahead == DONE || !current)
{
error << ' ' << boolean_syntax_errors[AT_END];
}
else
{
error << ' ' << boolean_syntax_errors[INSTEAD_OF] << " '"
<< current->word.get() << "'";
switch (lookahead)
{
case '&': error << ' ' << boolean_keywords[OR] << " '"
<< boolean_keywords[AND] << "'";
break;
case '|': error << ' ' << boolean_keywords[OR] << " '"
<< boolean_keywords[OR] << "'";
break;
case '!': error << ' ' << boolean_keywords[OR] << " '"
<< boolean_keywords[NOT] << "'";
break;
}
}
if (debug) cerr << "Syntax error: " << error << endl;
}
}
//*****************************************************************************
// Perform a lookup of the current word and push the result onto the stack
//
void
Parser::perform_push()
{
HtConfiguration* config= HtConfiguration::config();
static int maximum_word_length = config->Value("maximum_word_length", 12);
String temp = current->word.get();
char *p;
if(debug)
cerr << "perform_push @"<< stack.Size() << ": " << temp << endl;
String wildcard = config->Find("prefix_match_character");
if (!wildcard.get())
wildcard = "*";
if (temp == wildcard)
{
if (debug) cerr << "Wild card search\n";
ResultList *list = new ResultList;
String doc_db = config->Find("doc_db");
DocumentDB docdb;
docdb.Read(doc_db);
List *docs = docdb.DocIDs();
//
// Traverse all the known documents
//
DocumentRef *ref;
IntObject *id;
DocMatch *dm;
docs->Start_Get();
while ((id = (IntObject *) docs->Get_Next()))
{
ref = docdb[id->Value()];
if (debug)
cerr << (ref ? "Wildcard match" : "Wildcard empty") << endl;
if (ref)
{
dm = new DocMatch;
dm->score = current->weight;
dm->id = ref->DocID();
dm->orMatches = 1;
dm->anchor = 0;
list->add(dm);
}
delete ref;
}
delete docs;
stack.push(list);
return;
}
// Must be after wildcard: "*" is "isIgnore" because it is too short.
if (current->isIgnore)
{
if(debug) cerr << "ignore: " << temp << " @" << stack.Size() << endl;
//
// This word needs to be ignored. Make it so.
//
ResultList *list = new ResultList;
list->isIgnore = 1;
stack.push(list);
return;
}
temp.lowercase();
p = temp.get();
if (temp.length() > maximum_word_length)
p[maximum_word_length] = '\0';
List* result = words[p];
score(result, current->weight, current->flags);
delete result;
}
//*****************************************************************************
// BUG: Phrases containing "bad words" can have *any* "bad word" in that
// position. Words less than minimum_word_length ignored entirely,
// as they are not indexed.
void
Parser::perform_phrase(List * &oldWords)
{
HtConfiguration* config= HtConfiguration::config();
static int maximum_word_length = config->Value("maximum_word_length", 12);
String temp = current->word.get();
char *p;
List *newWords = 0;
HtWordReference *oldWord, *newWord;
// how many words ignored since last checked word?
static int ignoredWords = 0;
// if the query is empty, no further effort is needed
if(oldWords && oldWords->Count() == 0)
{
if(debug) cerr << "phrase not found, skip" << endl;
return;
}
if(debug) cerr << "phrase current: " << temp << endl;
if (current->isIgnore)
{
//
// This word needs to be ignored. Make it so.
//
if (temp.length() >= config->Value ("minimum_word_length") && oldWords)
ignoredWords++;
if(debug) cerr << "ignoring: " << temp << endl;
return;
}
temp.lowercase();
p = temp.get();
if (temp.length() > maximum_word_length)
p[maximum_word_length] = '\0';
newWords = words[p];
if(debug) cerr << "new words count: " << newWords->Count() << endl;
// If we don't have a prior list of words, we want this one...
if (!oldWords)
{
oldWords = new List;
if(debug) cerr << "phrase adding first: " << temp << endl;
newWords->Start_Get();
while ((newWord = (HtWordReference *) newWords->Get_Next()))
{
oldWords->Add(newWord);
}
if(debug) cerr << "old words count: " << oldWords->Count() << endl;
return;
}
// OK, now we have a previous list in wordList and a new list
List *results = new List;
Dictionary newDict(5000);
String nid;
newWords->Start_Get();
while ((newWord = (HtWordReference *) newWords->Get_Next()))
{
nid = "";
int did = newWord->DocID();
nid << did;
nid << "-";
int loc = newWord->Location();
nid << loc;
if (! newDict.Exists(nid)) {
newDict.Add(nid, (Object *)newWord);
} else {
// cerr << "perform_phrase: NewWords Duplicate: " << nid << "\n";
// Double addition is a problem if you don't want your original objects deleted
}
}
String oid;
oldWords->Start_Get();
while ((oldWord = (HtWordReference *) oldWords->Get_Next()))
{
oid = "";
int did = oldWord->DocID();
oid << did;
oid << "-";
int loc = oldWord->Location();
oid << loc + ignoredWords+1;
if (newDict.Exists(oid))
{
newWord = (HtWordReference *)newDict.Find(oid);
HtWordReference *result = new HtWordReference(*oldWord);
result->Flags(oldWord->Flags() & newWord->Flags());
result->Location(newWord->Location());
results->Add(result);
}
}
ignoredWords = 0; // most recent word is not a non-ignored word
newDict.Release();
if(debug) cerr << "old words count: " << oldWords->Count() << endl;
if(debug) cerr << "results count: " << results->Count() << endl;
oldWords->Destroy();
results->Start_Get();
while ((newWord = (HtWordReference *) results->Get_Next()))
{
oldWords->Add(newWord);
}
if(debug) cerr << "old words count: " << oldWords->Count() << endl;
results->Release();
delete results;
newWords->Destroy();
delete newWords;
}
//*****************************************************************************
// Allocate scores based on words in wordList.
// Fields within which the word must appear are specified in flags
// (see HtWordReference.h).
void
Parser::score(List *wordList, double weight, unsigned int flags)
{
HtConfiguration* config= HtConfiguration::config();
DocMatch *dm;
HtWordReference *wr;
static double text_factor = config->Double("text_factor", 1);
static double caps_factor = config->Double("caps_factor", 1);
static double title_factor = config->Double("title_factor", 1);
static double heading_factor = config->Double("heading_factor", 1);
static double keywords_factor = config->Double("keywords_factor", 1);
static double meta_description_factor = config->Double("meta_description_factor", 1);
static double author_factor = config->Double("author_factor", 1);
static double description_factor = config->Double("description_factor", 1);
double wscore;
int docanchor;
int word_count;
if (!wordList || wordList->Count() == 0)
{
// We can't score an empty list, so push a null pointer...
if(debug) cerr << "score: empty list, push 0 @" << stack.Size() << endl;
stack.push(0);
return;
}
ResultList *list = new ResultList;
if(debug) cerr << "score: push @" << stack.Size() << endl;
stack.push(list);
// We're now guaranteed to have a non-empty list
// We'll use the number of occurences of this word for scoring
word_count = wordList->Count();
wordList->Start_Get();
while ((wr = (HtWordReference *) wordList->Get_Next()))
{
//
// ******* Compute the score for the document
//
// If word not in one of the required fields, skip the entry.
// Plain text sets no flag in dbase, so treat it separately.
if (!(wr->Flags() & flags) && (wr->Flags() || !(flags & FLAG_PLAIN)))
{
if (debug > 2)
cerr << "Flags " << wr->Flags() << " lack " << flags << endl;
continue;
}
wscore = 0.0;
if (wr->Flags() == FLAG_TEXT) wscore += text_factor;
if (wr->Flags() & FLAG_CAPITAL) wscore += caps_factor;
if (wr->Flags() & FLAG_TITLE) wscore += title_factor;
if (wr->Flags() & FLAG_HEADING) wscore += heading_factor;
if (wr->Flags() & FLAG_KEYWORDS) wscore += keywords_factor;
if (wr->Flags() & FLAG_DESCRIPTION) wscore += meta_description_factor;
if (wr->Flags() & FLAG_AUTHOR) wscore += author_factor;
if (wr->Flags() & FLAG_LINK_TEXT) wscore += description_factor;
wscore *= weight;
wscore = wscore / (double)word_count;
docanchor = wr->Anchor();
dm = list->find(wr->DocID());
if (dm)
{
wscore += dm->score;
if (dm->anchor < docanchor)
docanchor = dm->anchor;
// We wish to *update* this, not add a duplicate
list->remove(wr->DocID());
}
dm = new DocMatch;
dm->id = wr->DocID();
dm->score = wscore;
dm->orMatches = 1; // how many "OR" terms this doc has
dm->anchor = docanchor;
list->add(dm);
}
}
//*****************************************************************************
// The top two entries in the stack need to be ANDed together.
//
// a b a and b
// 0 0 0
// 0 1 0
// 0 x 0
// 1 0 0
// 1 1 intersect(a,b)
// 1 x a
// x 0 0
// x 1 b
// x x x
//
void
Parser::perform_and()
{
ResultList *l1 = (ResultList *) stack.pop();
ResultList *l2 = (ResultList *) stack.pop();
int i;
DocMatch *dm, *dm2, *dm3;
HtVector *elements;
if(!(l2 && l1))
{
if(debug) cerr << "and: at least one empty operator, pushing 0 @" << stack.Size() << endl;
stack.push(0);
if(l1) delete l1;
if(l2) delete l2;
return;
}
//
// If either of the arguments is set to be ignored, we will use the
// other as the result.
// remember l2 and l1, l2 not l1
if (l1->isIgnore && l2->isIgnore)
{
if(debug) cerr << "and: ignoring all, pushing ignored list @" << stack.Size() << endl;
ResultList *result = new ResultList;
result->isIgnore = 1;
delete l1; delete l2;
stack.push(result);
return;
}
else if (l1->isIgnore)
{
if(debug) cerr << "and: ignoring l1, pushing l2 @" << stack.Size() << endl;
stack.push(l2);
delete l1;
return;
}
else if (l2->isIgnore)
{
if(debug) cerr << "and: ignoring l2, pushing l2 @" << stack.Size() << endl;
stack.push(l1);
delete l2;
return;
}
ResultList *result = new ResultList;
stack.push(result);
elements = l2->elements();
if(debug)
cerr << "perform and: " << elements->Count() << " " << l1->elements()->Count() << " ";
for (i = 0; i < elements->Count(); i++)
{
dm = (DocMatch *) (*elements)[i];
dm2 = l1->find(dm->id);
if (dm2)
{
//
// Duplicate document. Add scores and average "OR-matches" count
//
dm3 = new DocMatch;
// "if (dm2)" means "?:" operator not needed...
// dm3->score = dm->score + (dm2 ? dm2->score : 0);
// dm3->orMatches = (dm->orMatches + (dm2 ? dm2->orMatches : 0))/2;
dm3->score = dm->score + dm2->score;
dm3->orMatches = (dm->orMatches + dm2->orMatches)/2;
dm3->id = dm->id;
dm3->anchor = dm->anchor;
// if (dm2 && dm2->anchor < dm3->anchor)
if (dm2->anchor < dm3->anchor)
dm3->anchor = dm2->anchor;
result->add(dm3);
}
}
if(debug)
cerr << result->elements()->Count() << endl;
elements->Release();
delete elements;
delete l1;
delete l2;
}
// a b a not b
// 0 0 0
// 0 1 0
// 0 x 0
// 1 0 a
// 1 1 intersect(a,not b)
// 1 x a
// x 0 x
// x 1 x
// x x x
void
Parser::perform_not()
{
ResultList *l1 = (ResultList *) stack.pop();
ResultList *l2 = (ResultList *) stack.pop();
int i;
DocMatch *dm, *dm2, *dm3;
HtVector *elements;
if(!l2)
{
if(debug) cerr << "not: no positive term, pushing 0 @" << stack.Size() << endl;
// Should probably be interpreted as "* not l1"
stack.push(0);
if(l1) delete l1;
return;
}
if(!l1 || l1->isIgnore || l2->isIgnore)
{
if(debug) cerr << "not: no negative term, pushing positive @" << stack.Size() << endl;
stack.push(l2);
if(l1) delete l1;
return;
}
ResultList *result = new ResultList;
if(debug) cerr << "not: pushing result @" << stack.Size() << endl;
stack.push(result);
elements = l2->elements();
if(debug)
cerr << "perform not: " << elements->Count() << " " << l1->elements()->Count() << " ";
for (i = 0; i < elements->Count(); i++)
{
dm = (DocMatch *) (*elements)[i];
dm2 = l1->find(dm->id);
if (!dm2)
{
//
// Duplicate document.
//
dm3 = new DocMatch;
dm3->score = dm->score;
dm3->orMatches = dm->orMatches;
dm3->id = dm->id;
dm3->anchor = dm->anchor;
result->add(dm3);
}
}
if(debug)
cerr << result->elements()->Count() << endl;
elements->Release();
delete elements;
delete l1;
delete l2;
}
//*****************************************************************************
// The top two entries in the stack need to be ORed together.
//
void
Parser::perform_or()
{
ResultList *l1 = (ResultList *) stack.pop();
ResultList *result = (ResultList *) stack.peek();
int i;
DocMatch *dm, *dm2;
HtVector *elements;
//
// If either of the arguments is not present, we will use the other as
// the results.
//
if (!l1 && result)
{
if(debug) cerr << "or: no 2nd operand" << endl;
return; // result in top of stack
}
else if (l1 && !result)
{
if(debug) cerr << "or: no 1st operand" << endl;
stack.pop();
stack.push(l1);
return;
}
else if (!l1 && !result)
{
if(debug) cerr << "or: no operands" << endl;
stack.pop();
stack.push(0); // empty result
return;
}
//
// If either of the arguments is set to be ignored, we will use the
// other as the result.
//
if (l1->isIgnore)
{
delete l1;
return;
}
else if (result->isIgnore)
{
result = (ResultList *) stack.pop();
stack.push(l1);
delete result;
return;
}
elements = l1->elements();
if(debug)
cerr << "perform or: " << elements->Count() << " " << result->elements()->Count() << " ";
for (i = 0; i < elements->Count(); i++)
{
dm = (DocMatch *) (*elements)[i];
dm2 = result->find(dm->id);
if (dm2)
{
//
// Update document. Add scores and add "OR-match" counts
//
dm2->score += dm->score;
dm2->orMatches += dm->orMatches;
if (dm->anchor < dm2->anchor)
dm2->anchor = dm->anchor;
}
else
{
dm2 = new DocMatch;
dm2->score = dm->score;
dm2->orMatches = dm->orMatches;
dm2->id = dm->id;
dm2->anchor = dm->anchor;
result->add(dm2);
}
}
if(debug)
cerr << result->elements()->Count() << endl;
elements->Release();
delete elements;
delete l1;
}
//*****************************************************************************
// void Parser::parse(List *tokenList, ResultList &resultMatches)
//
void
Parser::parse(List *tokenList, ResultList &resultMatches)
{
HtConfiguration* config= HtConfiguration::config();
tokens = tokenList;
DocumentRef *ref = NULL;
fullexpr(1);
ResultList *result = (ResultList *) stack.pop();
if (!result) // Ouch!
{
// It seems we now end up here on a syntax error, so don't clear anything!
// valid = 0;
// error = 0;
// error << "Expected to have something to parse!";
return;
}
HtVector *elements = result->elements();
DocMatch *dm;
// multimatch_factor gives extra weight to matching documents which
// contain more than one "OR" term. This is applied after the whole
// document is parsed, so multiple matches don't give exponentially
// increasing weights
double multimatch_factor = config->Double("multimatch_factor");
for (int i = 0; i < elements->Count(); i++)
{
dm = (DocMatch *) (*elements)[i];
ref = collection->getDocumentRef(dm->GetId());
if(ref && ref->DocState() == Reference_normal)
{
dm->collection = collection; // back reference
if (dm->orMatches > 1)
dm->score *= 1+multimatch_factor;
resultMatches.add(dm);
}
}
elements->Release();
result->Release();
delete elements;
delete result;
}
void
Parser::setCollection(Collection *coll)
{
if (coll)
words.Open(coll->getWordFile(), O_RDONLY);
collection = coll;
}
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