my_compare.c

/* Copyright (c) 2011, Oracle and/or its affiliates.
   Copyright (c) 2009, 2020, MariaDB Corporation.

   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; version 2 of the License.

   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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335  USA */
   
#include <my_global.h>
#include <m_ctype.h>
#include <my_base.h>
#include <my_compare.h>
#include <my_sys.h>


static int compare_bin(const uchar *a, uint a_length,
                       const uchar *b, uint b_length,
                       my_bool part_key, my_bool skip_end_space)
{
  uint length= MY_MIN(a_length,b_length);
  const uchar *end= a+ length;
  int flag;

  while (a < end)
    if ((flag= (int) *a++ - (int) *b++))
      return flag;
  if (part_key && b_length < a_length)
    return 0;
  if (skip_end_space && a_length != b_length)
  {
    int swap= 1;
    /*
      We are using space compression. We have to check if longer key
      has next character < ' ', in which case it's less than the shorter
      key that has an implicit space afterwards.

      This code is identical to the one in
      strings/ctype-simple.c:my_strnncollsp_simple
    */
    if (a_length < b_length)
    {
      /* put shorter key in a */
      a_length= b_length;
      a= b;
      swap= -1;					/* swap sign of result */
    }
    for (end= a + a_length-length; a < end ; a++)
    {
      if (*a != ' ')
	return (*a < ' ') ? -swap : swap;
    }
    return 0;
  }
  return (int) (a_length-b_length);
}


/*
  Compare two keys

  SYNOPSIS
    ha_key_cmp()
    keyseg	Array of key segments of key to compare
    a		First key to compare, in format from _mi_pack_key()
		This is always from the row
    b		Second key to compare.  This is from the row or the user
    key_length	Length of key to compare, based on key b.  This can be shorter
		than b to just compare sub keys
    next_flag	How keys should be compared
		If bit SEARCH_FIND is not set the keys includes the row
		position and this should also be compared
                If SEARCH_PAGE_KEY_HAS_TRANSID is set then 'a' has transid
                If SEARCH_USER_KEY_HAS_TRANSID is set then 'b' has transid
    diff_pos    OUT Number of first keypart where values differ, counting 
                from one.
    diff_pos[1] OUT  (b + diff_pos[1]) points to first value in tuple b
                      that is different from corresponding value in tuple a.
  
  EXAMPLES 
   Example1: if the function is called for tuples
     ('aaa','bbb') and ('eee','fff'), then
     diff_pos[0] = 1 (as 'aaa' != 'eee')
     diff_pos[1] = 0 (offset from beginning of tuple b to 'eee' keypart).

   Example2: if the index function is called for tuples
     ('aaa','bbb') and ('aaa','fff'),
     diff_pos[0] = 2 (as 'aaa' != 'eee')
     diff_pos[1] = 3 (offset from beginning of tuple b to 'fff' keypart,
                      here we assume that first key part is CHAR(3) NOT NULL)

  NOTES
    Number-keys can't be splited

  RETURN VALUES
    <0	If a < b
    0	If a == b
    >0	If a > b
*/

#define FCMP(A,B) ((int) (A) - (int) (B))

int ha_key_cmp(HA_KEYSEG *keyseg, const uchar *a,
               const uchar *b, uint key_length, uint32 nextflag,
	       uint *diff_pos)
{
  int flag;
  int16 s_1,s_2;
  int32 l_1,l_2;
  uint32 u_1,u_2;
  float f_1,f_2;
  double d_1,d_2;
  uint next_key_length;
  const uchar *orig_b= b;

  *diff_pos=0;
  for ( ; (int) key_length >0 ; key_length=next_key_length, keyseg++)
  {
    const uchar *end;
    uint piks=! (keyseg->flag & HA_NO_SORT);
    (*diff_pos)++;
    diff_pos[1]= (uint)(b - orig_b);

    /* Handle NULL part */
    if (keyseg->null_bit)
    {
      key_length--;
      if (*a != *b && piks)
      {
        flag = (int) *a - (int) *b;
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      }
      b++;
      if (!*a++)                                /* If key was NULL */
      {
        if ((nextflag & (SEARCH_FIND | SEARCH_UPDATE | SEARCH_INSERT |
                         SEARCH_NULL_ARE_EQUAL)) ==
            (SEARCH_FIND | SEARCH_UPDATE | SEARCH_INSERT))
        {
          /* Allow duplicate keys */
          nextflag= (nextflag & ~(SEARCH_FIND | SEARCH_UPDATE)) | SEARCH_SAME;
        }
  	else if (nextflag & SEARCH_NULL_ARE_NOT_EQUAL)
	{
	  /*
	    This is only used from mi_check() to calculate cardinality.
	    It can't be used when searching for a key as this would cause
	    compare of (a,b) and (b,a) to return the same value.
	  */
	  return -1;
	}
        next_key_length=key_length;
        continue;                               /* To next key part */
      }
    }
    end= a+ MY_MIN(keyseg->length,key_length);
    next_key_length=key_length-keyseg->length;

    switch ((enum ha_base_keytype) keyseg->type) {
    case HA_KEYTYPE_TEXT:                       /* Ascii; Key is converted */
      if (keyseg->flag & HA_SPACE_PACK)
      {
        int a_length,b_length,pack_length;
        get_key_length(a_length,a);
        get_key_pack_length(b_length,pack_length,b);
        next_key_length=key_length-b_length-pack_length;

        if (piks &&
            (flag= ha_compare_char_fixed(keyseg->charset,
                                 a, a_length,
                                 b, b_length,
                                 keyseg->length / keyseg->charset->mbmaxlen,
                                 (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                            next_key_length <= 0))))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a+=a_length;
        b+=b_length;
        break;
      }
      else
      {
	uint length=(uint) (end-a), a_length=length, b_length=length;
        if (piks &&
            (flag= ha_compare_char_fixed(keyseg->charset,
                                 a, a_length,
                                 b, b_length,
                                 keyseg->length / keyseg->charset->mbmaxlen,
                                 (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                            next_key_length <= 0))))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a=end;
        b+=length;
      }
      break;
    case HA_KEYTYPE_BINARY:
    case HA_KEYTYPE_BIT:
      if (keyseg->flag & HA_SPACE_PACK)
      {
        int a_length,b_length,pack_length;
        get_key_length(a_length,a);
        get_key_pack_length(b_length,pack_length,b);
        next_key_length=key_length-b_length-pack_length;

        if (piks &&
	    (flag=compare_bin(a,a_length,b,b_length,
                              (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                         next_key_length <= 0),1)))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a+=a_length;
        b+=b_length;
        break;
      }
      else
      {
        uint length=keyseg->length;
        if (piks &&
	    (flag=compare_bin(a,length,b,length,
                              (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                         next_key_length <= 0),0)))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a+=length;
        b+=length;
      }
      break;
    case HA_KEYTYPE_VARTEXT1:
    case HA_KEYTYPE_VARTEXT2:
      {
        int a_length,b_length,pack_length;
        get_key_length(a_length,a);
        get_key_pack_length(b_length,pack_length,b);
        next_key_length=key_length-b_length-pack_length;

        if (piks &&
            (flag= ha_compare_char_varying(keyseg->charset,
                                   a, a_length,
                                   b, b_length,
                                   (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                              next_key_length <= 0))))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a+= a_length;
        b+= b_length;
        break;
      }
      break;
    case HA_KEYTYPE_VARBINARY1:
    case HA_KEYTYPE_VARBINARY2:
      {
        int a_length,b_length,pack_length;
        get_key_length(a_length,a);
        get_key_pack_length(b_length,pack_length,b);
        next_key_length=key_length-b_length-pack_length;

        if (piks &&
            (flag=compare_bin(a,a_length,b,b_length,
                              (my_bool) ((nextflag & SEARCH_PREFIX) &&
                                         next_key_length <= 0), 0)))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a+=a_length;
        b+=b_length;
      }
      break;
    case HA_KEYTYPE_INT8:
    {
      int i_1= (int) *((signed char*) a);
      int i_2= (int) *((signed char*) b);
      if (piks && (flag = CMP_NUM(i_1,i_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a= end;
      b++;
      break;
    }
    case HA_KEYTYPE_SHORT_INT:
      s_1= mi_sint2korr(a);
      s_2= mi_sint2korr(b);
      if (piks && (flag = CMP_NUM(s_1,s_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 2; /* sizeof(short int); */
      break;
    case HA_KEYTYPE_USHORT_INT:
      {
        uint16 us_1,us_2;
        us_1= mi_sint2korr(a);
        us_2= mi_sint2korr(b);
        if (piks && (flag = CMP_NUM(us_1,us_2)))
          return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
        a=  end;
        b+=2; /* sizeof(short int); */
        break;
      }
    case HA_KEYTYPE_LONG_INT:
      l_1= mi_sint4korr(a);
      l_2= mi_sint4korr(b);
      if (piks && (flag = CMP_NUM(l_1,l_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 4; /* sizeof(long int); */
      break;
    case HA_KEYTYPE_ULONG_INT:
      u_1= mi_sint4korr(a);
      u_2= mi_sint4korr(b);
      if (piks && (flag = CMP_NUM(u_1,u_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 4; /* sizeof(long int); */
      break;
    case HA_KEYTYPE_INT24:
      l_1=mi_sint3korr(a);
      l_2=mi_sint3korr(b);
      if (piks && (flag = CMP_NUM(l_1,l_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 3;
      break;
    case HA_KEYTYPE_UINT24:
      l_1=mi_uint3korr(a);
      l_2=mi_uint3korr(b);
      if (piks && (flag = CMP_NUM(l_1,l_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 3;
      break;
    case HA_KEYTYPE_FLOAT:
      mi_float4get(f_1,a);
      mi_float4get(f_2,b);
      /*
        The following may give a compiler warning about floating point
        comparison not being safe, but this is ok in this context as
        we are bascily doing sorting
      */
      if (piks && (flag = CMP_NUM(f_1,f_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 4; /* sizeof(float); */
      break;
    case HA_KEYTYPE_DOUBLE:
      mi_float8get(d_1,a);
      mi_float8get(d_2,b);
      /*
        The following may give a compiler warning about floating point
        comparison not being safe, but this is ok in this context as
        we are bascily doing sorting
      */
      if (piks && (flag = CMP_NUM(d_1,d_2)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 8;  /* sizeof(double); */
      break;
    case HA_KEYTYPE_NUM:                                /* Numeric key */
    {
      int swap_flag= 0;
      int alength,blength;

      if (keyseg->flag & HA_REVERSE_SORT)
      {
        swap_variables(const uchar*, a, b);
        swap_flag=1;                            /* Remember swap of a & b */
        end= a+ (int) (end-b);
      }
      if (keyseg->flag & HA_SPACE_PACK)
      {
        alength= *a++; blength= *b++;
        end=a+alength;
        next_key_length=key_length-blength-1;
      }
      else
      {
        alength= (int) (end-a);
        blength=keyseg->length;
        /* remove pre space from keys */
        for ( ; alength && *a == ' ' ; a++, alength--) ;
        for ( ; blength && *b == ' ' ; b++, blength--) ;
      }
      if (piks)
      {
	if (*a == '-')
	{
	  if (*b != '-')
	    return -1;
	  a++; b++;
	  swap_variables(const uchar*, a, b);
	  swap_variables(int, alength, blength);
	  swap_flag=1-swap_flag;
	  alength--; blength--;
	  end=a+alength;
	}
	else if (*b == '-')
	  return 1;
	while (alength && (*a == '+' || *a == '0'))
	{
	  a++; alength--;
	}
	while (blength && (*b == '+' || *b == '0'))
	{
	  b++; blength--;
	}
	if (alength != blength)
	  return (alength < blength) ? -1 : 1;
	while (a < end)
	  if (*a++ !=  *b++)
	    return ((int) a[-1] - (int) b[-1]);
      }
      else
      {
        b+=(end-a);
        a=end;
      }

      if (swap_flag)                            /* Restore pointers */
        swap_variables(const uchar*, a, b);
      break;
    }
#ifdef HAVE_LONG_LONG
    case HA_KEYTYPE_LONGLONG:
    {
      longlong ll_a,ll_b;
      ll_a= mi_sint8korr(a);
      ll_b= mi_sint8korr(b);
      if (piks && (flag = CMP_NUM(ll_a,ll_b)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 8;
      break;
    }
    case HA_KEYTYPE_ULONGLONG:
    {
      ulonglong ll_a,ll_b;
      ll_a= mi_uint8korr(a);
      ll_b= mi_uint8korr(b);
      if (piks && (flag = CMP_NUM(ll_a,ll_b)))
        return ((keyseg->flag & HA_REVERSE_SORT) ? -flag : flag);
      a=  end;
      b+= 8;
      break;
    }
#endif
    case HA_KEYTYPE_END:                        /* Ready */
      goto end;                                 /* diff_pos is incremented */
    }
  }
  (*diff_pos)++;
end:
  if (!(nextflag & SEARCH_FIND))
  {
    /*
      Compare rowid and possible transid
      This happens in the following case:
      - INSERT, UPDATE, DELETE when we have not unique keys or
        are using versioning
      - SEARCH_NEXT, SEARCH_PREVIOUS when we need to restart search

      The logic for comparing transid are as follows:
      Keys with have a transid have lowest bit in the rowidt. This means that
      if we are comparing a key with a transid with another key that doesn't
      have a tranid, we must reset the lowest bit for both keys.

      When we have transid, the keys are compared in transid order.
      A key without a transid is regared to be smaller than a key with
      a transid.
    */

    uint i;
    uchar key_mask, tmp_a, tmp_b;

    if (nextflag & (SEARCH_NO_FIND | SEARCH_LAST)) /* Find record after key */
      return (nextflag & (SEARCH_BIGGER | SEARCH_LAST)) ? -1 : 1;
    key_mask= (uchar) 255;

    if (!(nextflag & (SEARCH_USER_KEY_HAS_TRANSID |
                      SEARCH_PAGE_KEY_HAS_TRANSID)))
    {
      /*
        Neither key has a trid.  Only compare row id's and don't
        try to store rows in trid order
      */
      key_length= keyseg->length;
      nextflag&= ~SEARCH_INSERT;
    }
    else
    {
      /*
        Set key_mask so that we reset the last bit in the rowid before
        we compare it. This is needed as the lowest bit in the rowid is
        used to mark if the key has a transid or not.
      */
      key_mask= (uchar) 254;
      if (!test_all_bits(nextflag, (SEARCH_USER_KEY_HAS_TRANSID |
                                    SEARCH_PAGE_KEY_HAS_TRANSID)))
      {
        /*
          No transaction id for user key or for key on page 
          Ignore transid as at least one of the keys are visible for all
        */
        key_length= keyseg->length;
      }
      else
      {
        /*
          Both keys have trids. No need of special handling of incomplete
          trids below.
        */
        nextflag&= ~SEARCH_INSERT;
      }
    }
    DBUG_ASSERT(key_length > 0);

    for (i= key_length-1 ; (int) i-- > 0 ; )
    {
      if (*a++ != *b++)
      {
        flag= FCMP(a[-1],b[-1]);
        goto found;
      }
    }
    tmp_a= *a & key_mask;
    tmp_b= *b & key_mask;
    flag= FCMP(tmp_a, tmp_b);

    if (flag == 0 && (nextflag & SEARCH_INSERT))
    {
      /*
        Ensure that on insert we get rows stored in trid order.
        If one of the parts doesn't have a trid, this should be regarded
        as smaller than the other
      */
        return (nextflag & SEARCH_USER_KEY_HAS_TRANSID) ? -1 : 1;
    }
found:
    if (nextflag & SEARCH_SAME)
      return (flag);                            /* read same */
    if (nextflag & SEARCH_BIGGER)
      return (flag <= 0 ? -1 : 1);              /* read next */
    return (flag < 0 ? -1 : 1);                 /* read previous */
  }
  return 0;
} /* ha_key_cmp */

/*
  Find the first NULL value in index-suffix values tuple

  SYNOPSIS
    ha_find_null()
      keyseg     Array of keyparts for key suffix
      a          Key suffix value tuple

  DESCRIPTION
    Find the first NULL value in index-suffix values tuple.

  TODO
    Consider optimizing this function or its use so we don't search for
    NULL values in completely NOT NULL index suffixes.

  RETURN
    First key part that has NULL as value in values tuple, or the last key
    part (with keyseg->type==HA_TYPE_END) if values tuple doesn't contain
    NULLs.
*/

HA_KEYSEG *ha_find_null(HA_KEYSEG *keyseg, const uchar *a)
{
  for (; (enum ha_base_keytype) keyseg->type != HA_KEYTYPE_END; keyseg++)
  {
    const uchar *end;
    if (keyseg->null_bit)
    {
      if (!*a++)
        return keyseg;
    }
    end= a+ keyseg->length;

    switch ((enum ha_base_keytype) keyseg->type) {
    case HA_KEYTYPE_TEXT:
    case HA_KEYTYPE_BINARY:
    case HA_KEYTYPE_BIT:
      if (keyseg->flag & HA_SPACE_PACK)
      {
        int a_length;
        get_key_length(a_length, a);
        a += a_length;
        break;
      }
      else
        a= end;
      break;
    case HA_KEYTYPE_VARTEXT1:
    case HA_KEYTYPE_VARTEXT2:
    case HA_KEYTYPE_VARBINARY1:
    case HA_KEYTYPE_VARBINARY2:
      {
        int a_length;
        get_key_length(a_length, a);
        a+= a_length;
        break;
      }
    case HA_KEYTYPE_NUM:
      if (keyseg->flag & HA_SPACE_PACK)
      {
        int alength= *a++;
        end= a+alength;
      }
      a= end;
      break;
    case HA_KEYTYPE_INT8:
    case HA_KEYTYPE_SHORT_INT:
    case HA_KEYTYPE_USHORT_INT:
    case HA_KEYTYPE_LONG_INT:
    case HA_KEYTYPE_ULONG_INT:
    case HA_KEYTYPE_INT24:
    case HA_KEYTYPE_UINT24:
#ifdef HAVE_LONG_LONG
    case HA_KEYTYPE_LONGLONG:
    case HA_KEYTYPE_ULONGLONG:
#endif
    case HA_KEYTYPE_FLOAT:
    case HA_KEYTYPE_DOUBLE:
      a= end;
      break;
    case HA_KEYTYPE_END:                        /* purecov: inspected */
      /* keep compiler happy */
      DBUG_ASSERT(0);
      break;
    }
  }
  return keyseg;
}