~drizzle-trunk/drizzle/development

/* Copyright (C) 2000-2006 MySQL 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; 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 St, Fifth Floor, Boston, MA  02110-1301  USA */

/* Functions to check if a row is unique */

#include "myisam_priv.h"

#include <drizzled/charset.h>

using namespace drizzled;

bool mi_check_unique(MI_INFO *info,

                     MI_UNIQUEDEF *def,

                     unsigned char *record,

                     ha_checksum unique_hash,

                     internal::my_off_t disk_pos)

{

  internal::my_off_t lastpos=info->lastpos;

  MI_KEYDEF *key= &info->s->keyinfo[def->key];

  unsigned char *key_buff=info->lastkey2;

  mi_unique_store(record+key->seg->start, unique_hash);

  _mi_make_key(info,def->key,key_buff,record,0);

  /* The above changed info->lastkey2. Inform mi_rnext_same(). */

  info->update&= ~HA_STATE_RNEXT_SAME;

  if (_mi_search(info,info->s->keyinfo+def->key,key_buff,MI_UNIQUE_HASH_LENGTH,

		 SEARCH_FIND,info->s->state.key_root[def->key]))

  {

    info->page_changed=1;			/* Can't optimize read next */

    info->lastpos= lastpos;

    return(0);				/* No matching rows */

  }

  for (;;)

  {

    if (info->lastpos != disk_pos &&

	!(*info->s->compare_unique)(info,def,record,info->lastpos))

    {

      errno=HA_ERR_FOUND_DUPP_UNIQUE;

      info->errkey= (int) def->key;

      info->dupp_key_pos= info->lastpos;

      info->page_changed=1;			/* Can't optimize read next */

      info->lastpos=lastpos;

      return(1);				/* Found identical  */

    }

    if (_mi_search_next(info,info->s->keyinfo+def->key, info->lastkey,

			MI_UNIQUE_HASH_LENGTH, SEARCH_BIGGER,

			info->s->state.key_root[def->key]) ||

	memcmp(info->lastkey, key_buff, MI_UNIQUE_HASH_LENGTH))

    {

      info->page_changed=1;			/* Can't optimize read next */

      info->lastpos=lastpos;

      return(0);				/* end of tree */

    }

  }

}

/*

  Calculate a hash for a row

  TODO

    Add support for bit fields

*/

ha_checksum mi_unique_hash(MI_UNIQUEDEF *def, const unsigned char *record)

{

  const unsigned char *pos, *end;

  ha_checksum crc= 0;

  uint32_t seed1=0, seed2= 4;

  HA_KEYSEG *keyseg;

  for (keyseg=def->seg ; keyseg < def->end ; keyseg++)

  {

    enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type;

    uint32_t length=keyseg->length;

    if (keyseg->null_bit)

    {

      if (record[keyseg->null_pos] & keyseg->null_bit)

      {

	/*

	  Change crc in a way different from an empty string or 0.

	  (This is an optimisation;  The code will work even if this isn't

	  done)

	*/

	crc=((crc << 8) + 511+

	     (crc >> (8*sizeof(ha_checksum)-8)));

	continue;

      }

    }

    pos= record+keyseg->start;

    if (keyseg->flag & HA_VAR_LENGTH_PART)

    {

      uint32_t pack_length=  keyseg->bit_start;

      uint32_t tmp_length= (pack_length == 1 ? (uint) *(unsigned char*) pos :

                        uint2korr(pos));

      pos+= pack_length;			/* Skip VARCHAR length */

      set_if_smaller(length,tmp_length);

    }

    else if (keyseg->flag & HA_BLOB_PART)

    {

      uint32_t tmp_length=_mi_calc_blob_length(keyseg->bit_start,pos);

      memcpy(&pos,pos+keyseg->bit_start,sizeof(char*));

      if (!length || length > tmp_length)

	length=tmp_length;			/* The whole blob */

    }

    end= pos+length;

    if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT1 ||

        type == HA_KEYTYPE_VARTEXT2)

    {

      keyseg->charset->coll->hash_sort(keyseg->charset,

                                       (const unsigned char*) pos, length, &seed1,

                                       &seed2);

      crc^= seed1;

    }

    else

      while (pos != end)

	crc=((crc << 8) +

	     (((unsigned char)  *(unsigned char*) pos++))) +

	  (crc >> (8*sizeof(ha_checksum)-8));

  }

  return crc;

}

/*

  compare unique key for two rows

  TODO

    Add support for bit fields

  RETURN

    0   if both rows have equal unique value

    #   Rows are different

*/

int mi_unique_comp(MI_UNIQUEDEF *def, const unsigned char *a, const unsigned char *b,

		   bool null_are_equal)

{

  const unsigned char *pos_a, *pos_b, *end;

  HA_KEYSEG *keyseg;

  for (keyseg=def->seg ; keyseg < def->end ; keyseg++)

  {

    enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type;

    uint16_t a_length, b_length;

    a_length= b_length= keyseg->length;

    /* If part is NULL it's regarded as different */

    if (keyseg->null_bit)

    {

      uint32_t tmp;

      if ((tmp=(a[keyseg->null_pos] & keyseg->null_bit)) !=

	  (uint) (b[keyseg->null_pos] & keyseg->null_bit))

	return 1;

      if (tmp)

      {

	if (!null_are_equal)

	  return 1;

	continue;

      }

    }

    pos_a= a+keyseg->start;

    pos_b= b+keyseg->start;

    if (keyseg->flag & HA_VAR_LENGTH_PART)

    {

      uint32_t pack_length= keyseg->bit_start;

      if (pack_length == 1)

      {

        a_length= (uint) *(unsigned char*) pos_a++;

        b_length= (uint) *(unsigned char*) pos_b++;

      }

      else

      {

        a_length= uint2korr(pos_a);

        b_length= uint2korr(pos_b);

        pos_a+= 2;				/* Skip VARCHAR length */

        pos_b+= 2;

      }

      set_if_smaller(a_length, keyseg->length); /* Safety */

      set_if_smaller(b_length, keyseg->length); /* safety */

    }

    else if (keyseg->flag & HA_BLOB_PART)

    {

      /* Only compare 'length' characters if length != 0 */

      a_length= _mi_calc_blob_length(keyseg->bit_start,pos_a);

      b_length= _mi_calc_blob_length(keyseg->bit_start,pos_b);

      /* Check that a and b are of equal length */

      if (keyseg->length)

      {

        /*

          This is used in some cases when we are not interested in comparing

          the whole length of the blob.

        */

        set_if_smaller(a_length, keyseg->length);

        set_if_smaller(b_length, keyseg->length);

      }

      memcpy(&pos_a,pos_a+keyseg->bit_start,sizeof(char*));

      memcpy(&pos_b,pos_b+keyseg->bit_start,sizeof(char*));

    }

    if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT1 ||

        type == HA_KEYTYPE_VARTEXT2)

    {

      if (ha_compare_text(keyseg->charset, (unsigned char *) pos_a, a_length,

                                           (unsigned char *) pos_b, b_length, 0, 1))

        return 1;

    }

    else

    {

      if (a_length != b_length)

        return 1;

      end= pos_a+a_length;

      while (pos_a != end)

      {

	if (*pos_a++ != *pos_b++)

	  return 1;

      }

    }

  }

  return 0;

}