mariadb/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 */

#define FT_CORE
#include "ftdefs.h"
#include <queues.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                  /* MUST be 1                  */
#define FTB_FLAG_YES   2                  /* These two - YES and NO     */
#define FTB_FLAG_NO    4                  /*  should NEVER be set both  */

typedef struct st_ftb_expr FTB_EXPR;
struct st_ftb_expr {
  FTB_EXPR *up;
  byte     *quot, *qend;
  float     weight;
  uint      flags;
  my_off_t  docid[2];             /* for index search and for scan */
  float     cur_weight;
  int       yesses;               /* number of "yes" words matched */
  int       nos;                  /* number of "no"  words matched */
  int       ythresh;              /* number of "yes" words in expr */
  int       yweaks;               /* number of "yes" words for scan only */
};

typedef struct st_ftb_word {
  FTB_EXPR *up;
  float     weight;
  uint      flags;
  my_off_t  docid[2];             /* for index search and for scan */
  uint      ndepth;
  int       len;
  /* ... there can be docid cache added here. SerG */
  byte      word[1];
} FTB_WORD;

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

int FTB_WORD_cmp(void *v __attribute__((unused)), FTB_WORD *a, FTB_WORD *b)
{
  /* ORDER BY docid, ndepth DESC */
  int i=CMP_NUM(a->docid[0], b->docid[0]);
  if (!i)
    i=CMP_NUM(b->ndepth,a->ndepth);
  return i;
}

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, (*b)->word+1,(*b)->len-1,
                             (*a)->word+1,(*a)->len-1,0);
  if (!i)
    i=CMP_NUM((*b)->ndepth,(*a)->ndepth);
  return i;
}

void _ftb_parse_query(FTB *ftb, byte **start, byte *end,
                      FTB_EXPR *up, uint depth)
{
  byte        res;
  FTB_PARAM   param;
  FT_WORD     w;
  FTB_WORD   *ftbw;
  FTB_EXPR   *ftbe;
  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(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+extra));
        ftbw->len=w.len+1;
        ftbw->flags=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_POS_ERROR;
        ftbw->ndepth= (param.yesno<0) + depth;
        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);
        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->ythresh=ftbe->yweaks=0;
        ftbe->docid[0]=ftbe->docid[1]=HA_POS_ERROR;
        if ((ftbe->quot=param.quot)) ftb->with_scan|=2;
        if (param.yesno > 0) up->ythresh++;
        _ftb_parse_query(ftb, start, end, ftbe, depth+1);
        break;
      case 3: /* right bracket */
        if (up->quot) up->qend=param.quot;
        return;
    }
  }
  return;
}

void  _ftb_init_index_search(FT_INFO *ftb)
{
  int i, r;
  FTB_WORD   *ftbw;
  MI_INFO    *info=ftb->info;
  MI_KEYDEF  *keyinfo;
  my_off_t    keyroot;

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

  keyinfo=info->s->keyinfo+ftb->keynr;
  keyroot=info->s->state.key_root[ftb->keynr];

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

    if (ftbw->flags&FTB_FLAG_TRUNC &&
        (ftbw->up->ythresh > test(ftbw->flags&FTB_FLAG_YES)))
    {
      /* no need to search for this prefix in the index -
       * it cannot ADD new matches, and to REMOVE half-matched
       * rows we do scan anyway */
      ftbw->docid[0]=HA_POS_ERROR;
      ftbw->up->yweaks++;
      continue;
    }

    r=_mi_search(info, keyinfo, (uchar*) ftbw->word, ftbw->len,
                              SEARCH_FIND | SEARCH_BIGGER, keyroot);
    if (!r)
    {
      r=_mi_compare_text(ftb->charset,
                         info->lastkey + (ftbw->flags&FTB_FLAG_TRUNC),
                         ftbw->len     - (ftbw->flags&FTB_FLAG_TRUNC),
                         ftbw->word    + (ftbw->flags&FTB_FLAG_TRUNC),
                         ftbw->len     - (ftbw->flags&FTB_FLAG_TRUNC),
                         0);
    }
    if (r) /* not found */
    {
      if (ftbw->flags&FTB_FLAG_YES && ftbw->up->up==0)
      { /* this word MUST BE present in every document returned,
           so we can abort the search right now */
        ftb->state=INDEX_DONE;
        return;
      }
    }
    else
    {
      memcpy(ftbw->word, info->lastkey, info->lastkey_length);
      ftbw->docid[0]=info->lastpos;
    }
  }
  queue_fix(& ftb->queue);
}

FT_INFO * ft_init_boolean_search(MI_INFO *info, uint keynr, byte *query,
                    uint query_len, my_bool presort __attribute__((unused)))
{
  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= ((keynr==NO_SUCH_KEY) ?
    default_charset_info              :
    info->s->keyinfo[keynr].seg->charset);
  ftb->with_scan=0;

  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/(ft_min_word_len+1);
  ftb->queue.root=(byte **)alloc_root(&ftb->mem_root, (res+1)*sizeof(void*));
  reinit_queue(& ftb->queue, res, 0, 0,
                         (int (*)(void*,byte*,byte*))FTB_WORD_cmp, ftb);
  ftbe=(FTB_EXPR *)alloc_root(&ftb->mem_root, sizeof(FTB_EXPR));
  ftbe->weight=1;
  ftbe->flags=FTB_FLAG_YES;
  ftbe->nos=1;
  ftbe->quot=ftbe->up=0;
  ftbe->ythresh=ftbe->yweaks=0;
  ftbe->docid[0]=ftbe->docid[1]=HA_POS_ERROR;
  ftb->root=ftbe;
  _ftb_parse_query(ftb, &query, query+query_len, ftbe, 0);
  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;
}

/* returns 1 if str0 contain str1 */
int _ftb_strstr(const byte *s0, const byte *e0,
                const byte *s1, const byte *e1,
                CHARSET_INFO *cs)
{
  const byte *p;

  while (s0 < e0)
  {
    while (s0 < e0 && cs->to_upper[*s0++] != cs->to_upper[*s1])
      /* no-op */;
    if (s0 >= e0)
      return 0;
    p=s1+1;
    while (s0 < e0 && p < e1 && cs->to_upper[*s0++] == cs->to_upper[*p++])
      /* no-op */;
    if (p >= e1)
      return 1;
  }
  return 0;
}

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 (++ftbe->yesses == ythresh)
      {
        yn=ftbe->flags;
        weight=ftbe->cur_weight*ftbe->weight;
        if (mode && ftbe->quot)
        {
          int not_found=1;

          memcpy(&ftsi, ftsi_orig, sizeof(ftsi));
          while (_mi_ft_segiterator(&ftsi) && not_found)
          {
            if (!ftsi.pos)
              continue;
            not_found = ! _ftb_strstr(ftsi.pos, ftsi.pos+ftsi.len,
                                      ftbe->quot, ftbe->qend, 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 (ftbe->yesses < ythresh)
        break;
      yn= (ftbe->yesses++ == ythresh) ? ftbe->flags : 0 ;
      weight*=ftbe->weight;
    }
  }
}

int ft_boolean_read_next(FT_INFO *ftb, char *record)
{
  FTB_EXPR  *ftbe;
  FTB_WORD  *ftbw;
  MI_INFO   *info=ftb->info;
  MI_KEYDEF *keyinfo=info->s->keyinfo+ftb->keynr;
  my_off_t   keyroot=info->s->state.key_root[ftb->keynr];
  my_off_t   curdoc;
  int        r;

  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;

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

      /* update queue */
      r=_mi_search(info, keyinfo, (uchar*) ftbw->word, USE_WHOLE_KEY,
                   SEARCH_BIGGER , keyroot);
      if (!r)
      {
        r=_mi_compare_text(ftb->charset,
                           info->lastkey + (ftbw->flags&FTB_FLAG_TRUNC),
                           ftbw->len     - (ftbw->flags&FTB_FLAG_TRUNC),
                           ftbw->word    + (ftbw->flags&FTB_FLAG_TRUNC),
                           ftbw->len     - (ftbw->flags&FTB_FLAG_TRUNC),
                           0);
      }
      if (r) /* not found */
      {
        ftbw->docid[0]=HA_POS_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;
        }
      }
      else
      {
        memcpy(ftbw->word, info->lastkey, info->lastkey_length);
        ftbw->docid[0]=info->lastpos;
      }
      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 ! */
      info->lastpos=curdoc;
      info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED); /* why is this ? */

      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 */
        return 0;
      }
      return my_errno;
    }
  }
  ftb->state=INDEX_DONE;
  return my_errno=HA_ERR_END_OF_FILE;
}

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_POS_ERROR)
    return -2.0;
  if (!ftb->queue.elements)
    return 0;

  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((byte **)&ftsi.pos,(byte *)end,&word))
    {
      int a, b, c;
      for (a=0, b=ftb->queue.elements, c=(a+b)/2; b-a>1; c=(a+b)/2)
      {
        ftbw=(FTB_WORD *)(ftb->list[c]);
        if (_mi_compare_text(ftb->charset, word.pos,word.len,
                         (uchar*) ftbw->word+1,ftbw->len-1,
                         (ftbw->flags&FTB_FLAG_TRUNC) ) >0)
          b=c;
        else
          a=c;
      }
      for (; c>=0; c--)
      {
        ftbw=(FTB_WORD *)(ftb->list[c]);
        if (_mi_compare_text(ftb->charset, word.pos,word.len,
                         (uchar*) ftbw->word+1,ftbw->len-1,
                         (ftbw->flags&FTB_FLAG_TRUNC) ))
          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)
{
  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);
}