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Overview
Comment:Fix a bug in the spellfix extension causing it to compute suboptimal answers. The problem was introduced by check-in [afd6fbc01052ccfc9].
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SHA3-256: 3bf28fd9a70ebefc464dceda124d6ed342dd83f71eeeb0568f79e34e731a073e
User & Date: drh 2018-03-30 16:34:04
Context
2018-03-31
16:31
Fix an assertion failure triggered by a SELECT with a compound sub-query that contains an incorrectly placed ORDER BY clause. This problem is just an assert() failure - non-DEBUG builds are not affected. Problem found by OSSFuzz. check-in: 823779d3 user: dan tags: trunk
2018-03-30
16:34
Fix a bug in the spellfix extension causing it to compute suboptimal answers. The problem was introduced by check-in [afd6fbc01052ccfc9]. check-in: 3bf28fd9 user: drh tags: trunk
15:59
Fix an off-by-one error in the dist3 algorithm of the spellfix extension. check-in: 5c34af7b user: drh tags: trunk
Changes
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Changes to ext/misc/spellfix.c.

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}

/*
** Return TRUE (non-zero) if the To side of the given cost matches
** the given string.
*/
static int matchTo(EditDist3Cost *p, const char *z, int n){

  if( p->a[p->nFrom]!=z[0] ) return 0;
  if( p->nTo>n ) return 0;
  if( strncmp(p->a+p->nFrom, z, p->nTo)!=0 ) return 0;
  return 1;
}

/*
** Return TRUE (non-zero) if the From side of the given cost matches
** the given string.
*/
static int matchFrom(EditDist3Cost *p, const char *z, int n){
  assert( p->nFrom<=n );

  if( p->a[0]!=z[0] ) return 0;
  if( strncmp(p->a, z, p->nFrom)!=0 ) return 0;

  return 1;
}

/*
** Return TRUE (non-zero) of the next FROM character and the next TO
** character are the same.
*/
................................................................................
  EditDist3FromString *pStr,  /* Left hand string */
  int n1,                     /* Index of comparison character on the left */
  const char *z2,             /* Right-handl comparison character */
  int n2                      /* Bytes remaining in z2[] */
){
  int b1 = pStr->a[n1].nByte;
  if( b1>n2 ) return 0;

  if( pStr->z[n1]!=z2[0] ) return 0;
  if( strncmp(pStr->z+n1, z2, b1)!=0 ) return 0;
  return 1;
}

/*
** Delete an EditDist3FromString objecct







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}

/*
** Return TRUE (non-zero) if the To side of the given cost matches
** the given string.
*/
static int matchTo(EditDist3Cost *p, const char *z, int n){
  assert( n>0 );
  if( p->a[p->nFrom]!=z[0] ) return 0;
  if( p->nTo>n ) return 0;
  if( strncmp(p->a+p->nFrom, z, p->nTo)!=0 ) return 0;
  return 1;
}

/*
** Return TRUE (non-zero) if the From side of the given cost matches
** the given string.
*/
static int matchFrom(EditDist3Cost *p, const char *z, int n){
  assert( p->nFrom<=n );
  if( p->nFrom ){
    if( p->a[0]!=z[0] ) return 0;
    if( strncmp(p->a, z, p->nFrom)!=0 ) return 0;
  }
  return 1;
}

/*
** Return TRUE (non-zero) of the next FROM character and the next TO
** character are the same.
*/
................................................................................
  EditDist3FromString *pStr,  /* Left hand string */
  int n1,                     /* Index of comparison character on the left */
  const char *z2,             /* Right-handl comparison character */
  int n2                      /* Bytes remaining in z2[] */
){
  int b1 = pStr->a[n1].nByte;
  if( b1>n2 ) return 0;
  assert( b1>0 );
  if( pStr->z[n1]!=z2[0] ) return 0;
  if( strncmp(pStr->z+n1, z2, b1)!=0 ) return 0;
  return 1;
}

/*
** Delete an EditDist3FromString objecct