mariadb/storage/myisam/ft_boolean_search.c

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/* Written by Sergei A. Golubchik, who has a shared copyright to this code */

/*  TODO: add caching - pre-read several index entries at once */

/*
  Added optimization for full-text queries with plus-words. It was
  implemented by sharing maximal document id (max_docid) variable
  inside plus subtree. max_docid could be used by any word in plus
  subtree, but it could be updated by plus-word only.

  The idea is: there is no need to search for docid smaller than
  biggest docid inside current plus subtree.

  Examples:
  +word1 word2
    share same max_docid
    max_docid updated by word1
  +word1 +(word2 word3)
    share same max_docid
    max_docid updated by word1
  +(word1 -word2) +(+word3 word4)
    share same max_docid
    max_docid updated by word3
*/

#define FT_CORE
#include "ftdefs.h"

/* search with boolean queries */

static double _wghts[11]=
{
  0.131687242798354,
  0.197530864197531,
  0.296296296296296,
  0.444444444444444,
  0.666666666666667,
  1.000000000000000,
  1.500000000000000,
  2.250000000000000,
  3.375000000000000,
  5.062500000000000,
  7.593750000000000};
static double *wghts=_wghts+5; /* wghts[i] = 1.5**i */

static double _nwghts[11]=
{
 -0.065843621399177,
 -0.098765432098766,
 -0.148148148148148,
 -0.222222222222222,
 -0.333333333333334,
 -0.500000000000000,
 -0.750000000000000,
 -1.125000000000000,
 -1.687500000000000,
 -2.531250000000000,
 -3.796875000000000};
static double *nwghts=_nwghts+5; /* nwghts[i] = -0.5*1.5**i */

#define FTB_FLAG_TRUNC 1
/* At most one of the following flags can be set */
#define FTB_FLAG_YES   2
#define FTB_FLAG_NO    4
#define FTB_FLAG_WONLY 8

typedef struct st_ftb_expr FTB_EXPR;
struct st_ftb_expr
{
  FTB_EXPR *up;
  uint      flags;
/* ^^^^^^^^^^^^^^^^^^ FTB_{EXPR,WORD} common section */
  my_off_t  docid[2];
  my_off_t  max_docid;
  float     weight;
  float     cur_weight;
  LIST     *phrase;               /* phrase words */
  uint      yesses;               /* number of "yes" words matched */
  uint      nos;                  /* number of "no"  words matched */
  uint      ythresh;              /* number of "yes" words in expr */
  uint      yweaks;               /* number of "yes" words for scan only */
};

typedef struct st_ftb_word
{
  FTB_EXPR  *up;
  uint       flags;
/* ^^^^^^^^^^^^^^^^^^ FTB_{EXPR,WORD} common section */
  my_off_t   docid[2];             /* for index search and for scan */
  my_off_t   key_root;
  my_off_t  *max_docid;
  MI_KEYDEF *keyinfo;
  float      weight;
  uint       ndepth;
  uint       len;
  uchar      off;
  byte       word[1];
} FTB_WORD;

typedef struct st_ft_info
{
  struct _ft_vft *please;
  MI_INFO   *info;
  CHARSET_INFO *charset;
  FTB_EXPR  *root;
  FTB_WORD **list;
  MEM_ROOT   mem_root;
  QUEUE      queue;
  TREE       no_dupes;
  my_off_t   lastpos;
  uint       keynr;
  uchar      with_scan;
  enum { UNINITIALIZED, READY, INDEX_SEARCH, INDEX_DONE } state;
} FTB;

static int FTB_WORD_cmp(my_off_t *v, FTB_WORD *a, FTB_WORD *b)
{
  int i;

  /* if a==curdoc, take it as  a < b */
  if (v && a->docid[0] == *v)
    return -1;

  /* ORDER BY docid, ndepth DESC */
  i=CMP_NUM(a->docid[0], b->docid[0]);
  if (!i)
    i=CMP_NUM(b->ndepth,a->ndepth);
  return i;
}

static int FTB_WORD_cmp_list(CHARSET_INFO *cs, FTB_WORD **a, FTB_WORD **b)
{
  /* ORDER BY word DESC, ndepth DESC */
  int i= mi_compare_text(cs, (uchar*) (*b)->word+1,(*b)->len-1,
                             (uchar*) (*a)->word+1,(*a)->len-1,0,0);
  if (!i)
    i=CMP_NUM((*b)->ndepth,(*a)->ndepth);
  return i;
}

static void _ftb_parse_query(FTB *ftb, byte **start, byte *end,
                      FTB_EXPR *up, uint depth, byte *up_quot)
{
  byte        res;
  FTB_PARAM   param;
  FT_WORD     w;
  FTB_WORD   *ftbw;
  FTB_EXPR   *ftbe;
  FTB_EXPR   *tmp_expr;
  FT_WORD    *phrase_word;
  LIST       *phrase_list;
  uint  extra=HA_FT_WLEN+ftb->info->s->rec_reflength; /* just a shortcut */

  if (ftb->state != UNINITIALIZED)
    return;

  param.prev=' ';
  param.quot= up_quot;
  while ((res=ft_get_word(ftb->charset,start,end,&w,&param)))
  {
    int   r=param.plusminus;
    float weight= (float) (param.pmsign ? nwghts : wghts)[(r>5)?5:((r<-5)?-5:r)];
    switch (res) {
      case 1: /* word found */
        ftbw=(FTB_WORD *)alloc_root(&ftb->mem_root,
                                    sizeof(FTB_WORD) +
                                    (param.trunc ? MI_MAX_KEY_BUFF :
                                     w.len*ftb->charset->mbmaxlen+extra));
        ftbw->len=w.len+1;
        ftbw->flags=0;
        ftbw->off=0;
        if (param.yesno>0) ftbw->flags|=FTB_FLAG_YES;
        if (param.yesno<0) ftbw->flags|=FTB_FLAG_NO;
        if (param.trunc)   ftbw->flags|=FTB_FLAG_TRUNC;
        ftbw->weight=weight;
        ftbw->up=up;
        ftbw->docid[0]=ftbw->docid[1]=HA_OFFSET_ERROR;
        ftbw->ndepth= (param.yesno<0) + depth;
        ftbw->key_root=HA_OFFSET_ERROR;
        memcpy(ftbw->word+1, w.pos, w.len);
        ftbw->word[0]=w.len;
        if (param.yesno > 0) up->ythresh++;
        queue_insert(& ftb->queue, (byte *)ftbw);
        ftb->with_scan|=(param.trunc & FTB_FLAG_TRUNC);
        for (tmp_expr= up; tmp_expr->up; tmp_expr= tmp_expr->up)
          if (! (tmp_expr->flags & FTB_FLAG_YES))
            break;
        ftbw->max_docid= &tmp_expr->max_docid;
      case 4: /* not indexed word (stopword or too short/long) */
        if (! up_quot) break;
        phrase_word= (FT_WORD *)alloc_root(&ftb->mem_root, sizeof(FT_WORD));
        phrase_list= (LIST *)alloc_root(&ftb->mem_root, sizeof(LIST));
        phrase_word->pos= w.pos;
        phrase_word->len= w.len;
        phrase_list->data= (void *)phrase_word;
        up->phrase= list_add(up->phrase, phrase_list);
        break;
      case 2: /* left bracket */
        ftbe=(FTB_EXPR *)alloc_root(&ftb->mem_root, sizeof(FTB_EXPR));
        ftbe->flags=0;
        if (param.yesno>0) ftbe->flags|=FTB_FLAG_YES;
        if (param.yesno<0) ftbe->flags|=FTB_FLAG_NO;
        ftbe->weight=weight;
        ftbe->up=up;
        ftbe->max_docid= ftbe->ythresh= ftbe->yweaks= 0;
        ftbe->docid[0]=ftbe->docid[1]=HA_OFFSET_ERROR;
        ftbe->phrase= NULL;
        if (param.quot) ftb->with_scan|=2;
        if (param.yesno > 0) up->ythresh++;
        _ftb_parse_query(ftb, start, end, ftbe, depth+1, param.quot);
        param.quot=0;
        break;
      case 3: /* right bracket */
        if (up_quot) up->phrase= list_reverse(up->phrase);
        return;
    }
  }
  return;
}

static int _ftb_no_dupes_cmp(void* not_used __attribute__((unused)),
                             const void *a,const void *b)
{
  return CMP_NUM((*((my_off_t*)a)), (*((my_off_t*)b)));
}

/* returns 1 if the search was finished (must-word wasn't found) */
static int _ft2_search(FTB *ftb, FTB_WORD *ftbw, my_bool init_search)
{
  int r;
  int subkeys=1;
  my_bool can_go_down;
  MI_INFO *info=ftb->info;
  uint off, extra=HA_FT_WLEN+info->s->base.rec_reflength;
  byte *lastkey_buf=ftbw->word+ftbw->off;
  LINT_INIT(off);

  LINT_INIT(off);
  if (ftbw->flags & FTB_FLAG_TRUNC)
    lastkey_buf+=ftbw->len;

  if (init_search)
  {
    ftbw->key_root=info->s->state.key_root[ftb->keynr];
    ftbw->keyinfo=info->s->keyinfo+ftb->keynr;

    r=_mi_search(info, ftbw->keyinfo, (uchar*) ftbw->word, ftbw->len,
                 SEARCH_FIND | SEARCH_BIGGER, ftbw->key_root);
  }
  else
  {
    uint sflag= SEARCH_BIGGER;
    if (ftbw->docid[0] < *ftbw->max_docid)
    {
      sflag|= SEARCH_SAME;
      _mi_dpointer(info, (uchar *)(ftbw->word + ftbw->len + HA_FT_WLEN),
                   *ftbw->max_docid);
    }
    r=_mi_search(info, ftbw->keyinfo, (uchar*) lastkey_buf,
                   USE_WHOLE_KEY, sflag, ftbw->key_root);
  }

  can_go_down=(!ftbw->off && (init_search || (ftbw->flags & FTB_FLAG_TRUNC)));
  /* Skip rows inserted by concurrent insert */
  while (!r)
  {
    if (can_go_down)
    {
      /* going down ? */
      off=info->lastkey_length-extra;
      subkeys=ft_sintXkorr(info->lastkey+off);
    }
    if (subkeys<0 || info->lastpos < info->state->data_file_length)
      break;
    r= _mi_search_next(info, ftbw->keyinfo, info->lastkey,
                       info->lastkey_length,
		       SEARCH_BIGGER, ftbw->key_root);
  }

  if (!r && !ftbw->off)
  {
    r= mi_compare_text(ftb->charset,
                       info->lastkey+1,
                       info->lastkey_length-extra-1,
              (uchar*) ftbw->word+1,
                       ftbw->len-1,
             (my_bool) (ftbw->flags & FTB_FLAG_TRUNC),0);
  }

  if (r) /* not found */
  {
    if (!ftbw->off || !(ftbw->flags & FTB_FLAG_TRUNC))
    {
      ftbw->docid[0]=HA_OFFSET_ERROR;
      if ((ftbw->flags & FTB_FLAG_YES) && ftbw->up->up==0)
      {
        /*
          This word MUST BE present in every document returned,
          so we can stop the search right now
        */
        ftb->state=INDEX_DONE;
        return 1; /* search is done */
      }
      else
        return 0;
    }

    /* going up to the first-level tree to continue search there */
    _mi_dpointer(info, (uchar*) (lastkey_buf+HA_FT_WLEN), ftbw->key_root);
    ftbw->key_root=info->s->state.key_root[ftb->keynr];
    ftbw->keyinfo=info->s->keyinfo+ftb->keynr;
    ftbw->off=0;
    return _ft2_search(ftb, ftbw, 0);
  }

  /* matching key found */
  memcpy(lastkey_buf, info->lastkey, info->lastkey_length);
  if (lastkey_buf == ftbw->word)
    ftbw->len=info->lastkey_length-extra;

  /* going down ? */
  if (subkeys<0)
  {
    /*
      yep, going down, to the second-level tree
      TODO here: subkey-based optimization
    */
    ftbw->off=off;
    ftbw->key_root=info->lastpos;
    ftbw->keyinfo=& info->s->ft2_keyinfo;
    r=_mi_search_first(info, ftbw->keyinfo, ftbw->key_root);
    DBUG_ASSERT(r==0);  /* found something */
    memcpy(lastkey_buf+off, info->lastkey, info->lastkey_length);
  }
  ftbw->docid[0]=info->lastpos;
  if (ftbw->flags & FTB_FLAG_YES)
    *ftbw->max_docid= info->lastpos;
  return 0;
}

static void _ftb_init_index_search(FT_INFO *ftb)
{
  int i;
  FTB_WORD   *ftbw;

  if ((ftb->state != READY && ftb->state !=INDEX_DONE) ||
      ftb->keynr == NO_SUCH_KEY)
    return;
  ftb->state=INDEX_SEARCH;

  for (i=ftb->queue.elements; i; i--)
  {
    ftbw=(FTB_WORD *)(ftb->queue.root[i]);

    if (ftbw->flags & FTB_FLAG_TRUNC)
    {
      /*
        special treatment for truncation operator
        1. there are some (besides this) +words
           | no need to search in the index, it can never ADD new rows
           | to the result, and to remove half-matched rows we do scan anyway
        2. -trunc*
           | same as 1.
        3. in 1 and 2, +/- need not be on the same expr. level,
           but can be on any upper level, as in +word +(trunc1* trunc2*)
        4. otherwise
           | We have to index-search for this prefix.
           | It may cause duplicates, as in the index (sorted by <word,docid>)
           |   <aaaa,row1>
           |   <aabb,row2>
           |   <aacc,row1>
           | Searching for "aa*" will find row1 twice...
      */
      FTB_EXPR *ftbe;
      for (ftbe=(FTB_EXPR*)ftbw;
           ftbe->up && !(ftbe->up->flags & FTB_FLAG_TRUNC);
           ftbe->up->flags|= FTB_FLAG_TRUNC, ftbe=ftbe->up)
      {
        if (ftbe->flags & FTB_FLAG_NO ||                     /* 2 */
             ftbe->up->ythresh - ftbe->up->yweaks >1)        /* 1 */
        {
          FTB_EXPR *top_ftbe=ftbe->up;
          ftbw->docid[0]=HA_OFFSET_ERROR;
          for (ftbe=(FTB_EXPR *)ftbw;
               ftbe != top_ftbe && !(ftbe->flags & FTB_FLAG_NO);
               ftbe=ftbe->up)
              ftbe->up->yweaks++;
          ftbe=0;
          break;
        }
      }
      if (!ftbe)
        continue;
      /* 4 */
      if (!is_tree_inited(& ftb->no_dupes))
        init_tree(& ftb->no_dupes,0,0,sizeof(my_off_t),
            _ftb_no_dupes_cmp,0,0,0);
      else
        reset_tree(& ftb->no_dupes);
    }

    ftbw->off=0; /* in case of reinit */
    if (_ft2_search(ftb, ftbw, 1))
      return;
  }
  queue_fix(& ftb->queue);
}


FT_INFO * ft_init_boolean_search(MI_INFO *info, uint keynr, byte *query,
                                 uint query_len, CHARSET_INFO *cs)
{
  FTB       *ftb;
  FTB_EXPR  *ftbe;
  uint       res;

  if (!(ftb=(FTB *)my_malloc(sizeof(FTB), MYF(MY_WME))))
    return 0;
  ftb->please= (struct _ft_vft *) & _ft_vft_boolean;
  ftb->state=UNINITIALIZED;
  ftb->info=info;
  ftb->keynr=keynr;
  ftb->charset=cs;
  DBUG_ASSERT(keynr==NO_SUCH_KEY || cs == info->s->keyinfo[keynr].seg->charset);
  ftb->with_scan=0;
  ftb->lastpos=HA_OFFSET_ERROR;
  bzero(& ftb->no_dupes, sizeof(TREE));

  init_alloc_root(&ftb->mem_root, 1024, 1024);

  /*
    Hack: instead of init_queue, we'll use reinit queue to be able
    to alloc queue with alloc_root()
  */
  res=ftb->queue.max_elements=1+query_len/2;
  if (!(ftb->queue.root=
        (byte **)alloc_root(&ftb->mem_root, (res+1)*sizeof(void*))))
    goto err;
  reinit_queue(& ftb->queue, res, 0, 0,
                         (int (*)(void*,byte*,byte*))FTB_WORD_cmp, 0);
  if (!(ftbe=(FTB_EXPR *)alloc_root(&ftb->mem_root, sizeof(FTB_EXPR))))
    goto err;
  ftbe->weight=1;
  ftbe->flags=FTB_FLAG_YES;
  ftbe->nos=1;
  ftbe->up=0;
  ftbe->max_docid= ftbe->ythresh= ftbe->yweaks= 0;
  ftbe->docid[0]=ftbe->docid[1]=HA_OFFSET_ERROR;
  ftbe->phrase= NULL;
  ftb->root=ftbe;
  _ftb_parse_query(ftb, &query, query+query_len, ftbe, 0, NULL);
  ftb->list=(FTB_WORD **)alloc_root(&ftb->mem_root,
                                     sizeof(FTB_WORD *)*ftb->queue.elements);
  memcpy(ftb->list, ftb->queue.root+1, sizeof(FTB_WORD *)*ftb->queue.elements);
  qsort2(ftb->list, ftb->queue.elements, sizeof(FTB_WORD *),
                              (qsort2_cmp)FTB_WORD_cmp_list, ftb->charset);
  if (ftb->queue.elements<2) ftb->with_scan &= ~FTB_FLAG_TRUNC;
  ftb->state=READY;
  return ftb;
err:
  free_root(& ftb->mem_root, MYF(0));
  my_free((gptr)ftb,MYF(0));
  return 0;
}


/*
  Checks if given buffer matches phrase list.

  SYNOPSIS
    _ftb_check_phrase()
    s0     start of buffer
    e0     end of buffer
    phrase broken into list phrase
    cs     charset info

  RETURN VALUE
    1 is returned if phrase found, 0 else.
*/

static int _ftb_check_phrase(const byte *s0, const byte *e0,
                LIST *phrase, CHARSET_INFO *cs)
{
  FT_WORD h_word;
  const byte *h_start= s0;
  DBUG_ENTER("_ftb_strstr");
  DBUG_ASSERT(phrase);

  while (ft_simple_get_word(cs, (byte **)&h_start, e0, &h_word, FALSE))
  {
    FT_WORD *n_word;
    LIST *phrase_element= phrase;
    const byte *h_start1= h_start;
    for (;;)
    {
      n_word= (FT_WORD *)phrase_element->data;
      if (my_strnncoll(cs, h_word.pos, h_word.len, n_word->pos, n_word->len))
        break;
      if (! (phrase_element= phrase_element->next))
        DBUG_RETURN(1);
      if (! ft_simple_get_word(cs, (byte **)&h_start1, e0, &h_word, FALSE))
        DBUG_RETURN(0);
    }
  }
  DBUG_RETURN(0);
}


static void _ftb_climb_the_tree(FTB *ftb, FTB_WORD *ftbw, FT_SEG_ITERATOR *ftsi_orig)
{
  FT_SEG_ITERATOR ftsi;
  FTB_EXPR *ftbe;
  float weight=ftbw->weight;
  int  yn=ftbw->flags, ythresh, mode=(ftsi_orig != 0);
  my_off_t curdoc=ftbw->docid[mode];

  for (ftbe=ftbw->up; ftbe; ftbe=ftbe->up)
  {
    ythresh = ftbe->ythresh - (mode ? 0 : ftbe->yweaks);
    if (ftbe->docid[mode] != curdoc)
    {
      ftbe->cur_weight=0;
      ftbe->yesses=ftbe->nos=0;
      ftbe->docid[mode]=curdoc;
    }
    if (ftbe->nos)
      break;
    if (yn & FTB_FLAG_YES)
    {
      weight /= ftbe->ythresh;
      ftbe->cur_weight += weight;
      if ((int) ++ftbe->yesses == ythresh)
      {
        yn=ftbe->flags;
        weight=ftbe->cur_weight*ftbe->weight;
        if (mode && ftbe->phrase)
        {
          int not_found=1;

          memcpy(&ftsi, ftsi_orig, sizeof(ftsi));
          while (_mi_ft_segiterator(&ftsi) && not_found)
          {
            if (!ftsi.pos)
              continue;
            not_found = ! _ftb_check_phrase(ftsi.pos, ftsi.pos+ftsi.len,
                                      ftbe->phrase, ftb->charset);
          }
          if (not_found) break;
        } /* ftbe->quot */
      }
      else
        break;
    }
    else
    if (yn & FTB_FLAG_NO)
    {
      /*
        NOTE: special sort function of queue assures that all
        (yn & FTB_FLAG_NO) != 0
        events for every particular subexpression will
        "auto-magically" happen BEFORE all the
        (yn & FTB_FLAG_YES) != 0 events. So no
        already matched expression can become not-matched again.
      */
      ++ftbe->nos;
      break;
    }
    else
    {
      if (ftbe->ythresh)
        weight/=3;
      ftbe->cur_weight +=  weight;
      if ((int) ftbe->yesses < ythresh)
        break;
      if (!(yn & FTB_FLAG_WONLY))
        yn= ((int) ftbe->yesses++ == ythresh) ? ftbe->flags : FTB_FLAG_WONLY ;
      weight*= ftbe->weight;
    }
  }
}


int ft_boolean_read_next(FT_INFO *ftb, char *record)
{
  FTB_EXPR  *ftbe;
  FTB_WORD  *ftbw;
  MI_INFO   *info=ftb->info;
  my_off_t   curdoc;

  if (ftb->state != INDEX_SEARCH && ftb->state != INDEX_DONE)
    return -1;

  /* black magic ON */
  if ((int) _mi_check_index(info, ftb->keynr) < 0)
    return my_errno;
  if (_mi_readinfo(info, F_RDLCK, 1))
    return my_errno;
  /* black magic OFF */

  if (!ftb->queue.elements)
    return my_errno=HA_ERR_END_OF_FILE;

  /* Attention!!! Address of a local variable is used here! See err: label */
  ftb->queue.first_cmp_arg=(void *)&curdoc;

  while (ftb->state == INDEX_SEARCH &&
         (curdoc=((FTB_WORD *)queue_top(& ftb->queue))->docid[0]) !=
         HA_OFFSET_ERROR)
  {
    while (curdoc == (ftbw=(FTB_WORD *)queue_top(& ftb->queue))->docid[0])
    {
      _ftb_climb_the_tree(ftb, ftbw, 0);

      /* update queue */
      _ft2_search(ftb, ftbw, 0);
      queue_replaced(& ftb->queue);
    }

    ftbe=ftb->root;
    if (ftbe->docid[0]==curdoc && ftbe->cur_weight>0 &&
        ftbe->yesses>=(ftbe->ythresh-ftbe->yweaks) && !ftbe->nos)
    {
      /* curdoc matched ! */
      if (is_tree_inited(&ftb->no_dupes) &&
          tree_insert(&ftb->no_dupes, &curdoc, 0,
                      ftb->no_dupes.custom_arg)->count >1)
        /* but it managed already to get past this line once */
        continue;

      info->lastpos=curdoc;
      /* Clear all states, except that the table was updated */
      info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);

      if (!(*info->read_record)(info,curdoc,record))
      {
        info->update|= HA_STATE_AKTIV;          /* Record is read */
        if (ftb->with_scan && ft_boolean_find_relevance(ftb,record,0)==0)
            continue; /* no match */
        my_errno=0;
        goto err;
      }
      goto err;
    }
  }
  ftb->state=INDEX_DONE;
  my_errno=HA_ERR_END_OF_FILE;
err:
  ftb->queue.first_cmp_arg=(void *)0;
  return my_errno;
}


float ft_boolean_find_relevance(FT_INFO *ftb, byte *record, uint length)
{
  FT_WORD word;
  FTB_WORD *ftbw;
  FTB_EXPR *ftbe;
  FT_SEG_ITERATOR ftsi, ftsi2;
  const byte *end;
  my_off_t  docid=ftb->info->lastpos;

  if (docid == HA_OFFSET_ERROR)
    return -2.0;
  if (!ftb->queue.elements)
    return 0;

  if (ftb->state != INDEX_SEARCH && docid <= ftb->lastpos)
  {
    FTB_EXPR *x;
    uint i;

    for (i=0; i < ftb->queue.elements; i++)
    {
      ftb->list[i]->docid[1]=HA_OFFSET_ERROR;
      for (x=ftb->list[i]->up; x; x=x->up)
        x->docid[1]=HA_OFFSET_ERROR;
    }
  }

  ftb->lastpos=docid;

  if (ftb->keynr==NO_SUCH_KEY)
    _mi_ft_segiterator_dummy_init(record, length, &ftsi);
  else
    _mi_ft_segiterator_init(ftb->info, ftb->keynr, record, &ftsi);
  memcpy(&ftsi2, &ftsi, sizeof(ftsi));

  while (_mi_ft_segiterator(&ftsi))
  {
    if (!ftsi.pos)
      continue;

    end=ftsi.pos+ftsi.len;
    while (ft_simple_get_word(ftb->charset, (byte **) &ftsi.pos,
                              (byte *) end, &word, TRUE))
    {
      int a, b, c;
      for (a=0, b=ftb->queue.elements, c=(a+b)/2; b-a>1; c=(a+b)/2)
      {
        ftbw=ftb->list[c];
        if (mi_compare_text(ftb->charset, (uchar*) word.pos, word.len,
                            (uchar*) ftbw->word+1, ftbw->len-1,
                            (my_bool) (ftbw->flags&FTB_FLAG_TRUNC),0) >0)
          b=c;
        else
          a=c;
      }
      for (; c>=0; c--)
      {
        ftbw=ftb->list[c];
        if (mi_compare_text(ftb->charset, (uchar*) word.pos, word.len,
                            (uchar*) ftbw->word+1,ftbw->len-1,
                            (my_bool) (ftbw->flags&FTB_FLAG_TRUNC),0))
          break;
        if (ftbw->docid[1] == docid)
          continue;
        ftbw->docid[1]=docid;
        _ftb_climb_the_tree(ftb, ftbw, &ftsi2);
      }
    }
  }

  ftbe=ftb->root;
  if (ftbe->docid[1]==docid && ftbe->cur_weight>0 &&
      ftbe->yesses>=ftbe->ythresh && !ftbe->nos)
  { /* row matched ! */
    return ftbe->cur_weight;
  }
  else
  { /* match failed ! */
    return 0.0;
  }
}


void ft_boolean_close_search(FT_INFO *ftb)
{
  if (is_tree_inited(& ftb->no_dupes))
  {
    delete_tree(& ftb->no_dupes);
  }
  free_root(& ftb->mem_root, MYF(0));
  my_free((gptr)ftb,MYF(0));
}


float ft_boolean_get_relevance(FT_INFO *ftb)
{
  return ftb->root->cur_weight;
}


void ft_boolean_reinit_search(FT_INFO *ftb)
{
  _ftb_init_index_search(ftb);
}