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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 16:34:04.007
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: 823779d31e 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: 3bf28fd9a7 user: drh tags: trunk)
15:59
Fix an off-by-one error in the dist3 algorithm of the spellfix extension. (check-in: 5c34af7b97 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
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.
*/
static int matchFromTo(
  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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831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877

}

/*
** 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.
*/
static int matchFromTo(
  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
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