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/* 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/* Functions to handle keys and fields in forms */

#include "mysql_priv.h"

/*
  Search after a key that starts with 'field'

  SYNOPSIS
    find_ref_key()
    key			First key to check
    key_count		How many keys to check
    record		Start of record
    field		Field to search after
    key_length		On partial match, contains length of fields before
			field
    keypart             key part # of a field

  NOTES
   Used when calculating key for NEXT_NUMBER

  IMPLEMENTATION
    If no key starts with field test if field is part of some key. If we find
    one, then return first key and set key_length to the number of bytes
    preceding 'field'.

  RETURN
   -1  field is not part of the key
   #   Key part for key matching key.
       key_length is set to length of key before (not including) field
*/

int find_ref_key(KEY *key, uint key_count, uchar *record, Field *field,
                 uint *key_length, uint *keypart)
{
  register int i;
  register KEY *key_info;
  uint fieldpos;

  fieldpos= field->offset(record);

  /* Test if some key starts as fieldpos */
  for (i= 0, key_info= key ;
       i < (int) key_count ;
       i++, key_info++)
  {
    if (key_info->key_part[0].offset == fieldpos)
    {                                  		/* Found key. Calc keylength */
      *key_length= *keypart= 0;
      return i;                                 /* Use this key */
    }
  }

  /* Test if some key contains fieldpos */
  for (i= 0, key_info= key;
       i < (int) key_count ;
       i++, key_info++)
  {
    uint j;
    KEY_PART_INFO *key_part;
    *key_length=0;
    for (j=0, key_part=key_info->key_part ;
	 j < key_info->key_parts ;
	 j++, key_part++)
    {
      if (key_part->offset == fieldpos)
      {
        *keypart= j;
        return i;                               /* Use this key */
      }
      *key_length+= key_part->store_length;
    }
  }
  return(-1);					/* No key is ok */
}


/**
  Copy part of a record that forms a key or key prefix to a buffer.

    The function takes a complete table record (as e.g. retrieved by
    handler::index_read()), and a description of an index on the same table,
    and extracts the first key_length bytes of the record which are part of a
    key into to_key. If length == 0 then copy all bytes from the record that
    form a key.

  @param to_key      buffer that will be used as a key
  @param from_record full record to be copied from
  @param key_info    descriptor of the index
  @param key_length  specifies length of all keyparts that will be copied
*/

void key_copy(uchar *to_key, uchar *from_record, KEY *key_info,
              uint key_length)
{
  uint length;
  KEY_PART_INFO *key_part;

  if (key_length == 0)
    key_length= key_info->key_length;
  for (key_part= key_info->key_part; (int) key_length > 0; key_part++)
  {
    if (key_part->null_bit)
    {
      *to_key++= test(from_record[key_part->null_offset] &
		   key_part->null_bit);
      key_length--;
    }
    if (key_part->key_part_flag & HA_BLOB_PART ||
        key_part->key_part_flag & HA_VAR_LENGTH_PART)
    {
      key_length-= HA_KEY_BLOB_LENGTH;
      length= min(key_length, key_part->length);
      key_part->field->get_key_image(to_key, length, Field::itRAW);
      to_key+= HA_KEY_BLOB_LENGTH;
    }
    else
    {
      length= min(key_length, key_part->length);
      Field *field= key_part->field;
      CHARSET_INFO *cs= field->charset();
      uint bytes= field->get_key_image(to_key, length, Field::itRAW);
      if (bytes < length)
        cs->cset->fill(cs, (char*) to_key + bytes, length - bytes, ' ');
    }
    to_key+= length;
    key_length-= length;
  }
}


/**
  Zero the null components of key tuple.
*/

void key_zero_nulls(uchar *tuple, KEY *key_info)
{
  KEY_PART_INFO *key_part= key_info->key_part;
  KEY_PART_INFO *key_part_end= key_part + key_info->key_parts;
  for (; key_part != key_part_end; key_part++)
  {
    if (key_part->null_bit && *tuple)
      bzero(tuple+1, key_part->store_length-1);
    tuple+= key_part->store_length;
  }
}


/*
  Restore a key from some buffer to record.

    This function converts a key into record format. It can be used in cases
    when we want to return a key as a result row.

  @param to_record   record buffer where the key will be restored to
  @param from_key    buffer that contains a key
  @param key_info    descriptor of the index
  @param key_length  specifies length of all keyparts that will be restored
*/

void key_restore(uchar *to_record, uchar *from_key, KEY *key_info,
                 uint key_length)
{
  uint length;
  KEY_PART_INFO *key_part;

  if (key_length == 0)
  {
    key_length= key_info->key_length;
  }
  for (key_part= key_info->key_part ; (int) key_length > 0 ; key_part++)
  {
    uchar used_uneven_bits= 0;
    if (key_part->null_bit)
    {
      if (*from_key++)
	to_record[key_part->null_offset]|= key_part->null_bit;
      else
	to_record[key_part->null_offset]&= ~key_part->null_bit;
      key_length--;
    }
    if (key_part->type == HA_KEYTYPE_BIT)
    {
      Field_bit *field= (Field_bit *) (key_part->field);
      if (field->bit_len)
      {
        uchar bits= *(from_key + key_part->length -
                      field->pack_length_in_rec() - 1);
        set_rec_bits(bits, to_record + key_part->null_offset +
                     (key_part->null_bit == 128),
                     field->bit_ofs, field->bit_len);
        /* we have now used the byte with 'uneven' bits */
        used_uneven_bits= 1;
      }
    }
    if (key_part->key_part_flag & HA_BLOB_PART)
    {
      /*
        This in fact never happens, as we have only partial BLOB
        keys yet anyway, so it's difficult to find any sence to
        restore the part of a record.
        Maybe this branch is to be removed, but now we
        have to ignore GCov compaining.
      */
      uint blob_length= uint2korr(from_key);
      Field_blob *field= (Field_blob*) key_part->field;
      from_key+= HA_KEY_BLOB_LENGTH;
      key_length-= HA_KEY_BLOB_LENGTH;
      field->set_ptr_offset(to_record - field->table->record[0],
                            (ulong) blob_length, from_key);
      length= key_part->length;
    }
    else if (key_part->key_part_flag & HA_VAR_LENGTH_PART)
    {
      Field *field= key_part->field;
      my_bitmap_map *old_map;
      my_ptrdiff_t ptrdiff= to_record - field->table->record[0];
      field->move_field_offset(ptrdiff);
      key_length-= HA_KEY_BLOB_LENGTH;
      length= min(key_length, key_part->length);
      old_map= dbug_tmp_use_all_columns(field->table, field->table->write_set);
      field->set_key_image(from_key, length);
      dbug_tmp_restore_column_map(field->table->write_set, old_map);
      from_key+= HA_KEY_BLOB_LENGTH;
      field->move_field_offset(-ptrdiff);
    }
    else
    {
      length= min(key_length, key_part->length);
      /* skip the byte with 'uneven' bits, if used */
      memcpy(to_record + key_part->offset, from_key + used_uneven_bits
             , (size_t) length - used_uneven_bits);
    }
    from_key+= length;
    key_length-= length;
  }
}


/**
  Compare if a key has changed.

  @param table		TABLE
  @param key		key to compare to row
  @param idx		Index used
  @param key_length	Length of key

  @note
    In theory we could just call field->cmp() for all field types,
    but as we are only interested if a key has changed (not if the key is
    larger or smaller than the previous value) we can do things a bit
    faster by using memcmp() instead.

  @retval
    0	If key is equal
  @retval
    1	Key has changed
*/

bool key_cmp_if_same(TABLE *table,const uchar *key,uint idx,uint key_length)
{
  uint store_length;
  KEY_PART_INFO *key_part;
  const uchar *key_end= key + key_length;;

  for (key_part=table->key_info[idx].key_part;
       key < key_end ; 
       key_part++, key+= store_length)
  {
    uint length;
    store_length= key_part->store_length;

    if (key_part->null_bit)
    {
      if (*key != test(table->record[0][key_part->null_offset] & 
		       key_part->null_bit))
	return 1;
      if (*key)
	continue;
      key++;
      store_length--;
    }
    if (key_part->key_part_flag & (HA_BLOB_PART | HA_VAR_LENGTH_PART |
                                   HA_BIT_PART))
    {
      if (key_part->field->key_cmp(key, key_part->length))
	return 1;
      continue;
    }
    length= min((uint) (key_end-key), store_length);
    if (!(key_part->key_type & (FIELDFLAG_NUMBER+FIELDFLAG_BINARY+
                                FIELDFLAG_PACK)))
    {
      CHARSET_INFO *cs= key_part->field->charset();
      uint char_length= key_part->length / cs->mbmaxlen;
      const uchar *pos= table->record[0] + key_part->offset;
      if (length > char_length)
      {
        char_length= my_charpos(cs, pos, pos + length, char_length);
        set_if_smaller(char_length, length);
      }
      if (cs->coll->strnncollsp(cs,
                                (const uchar*) key, length,
                                (const uchar*) pos, char_length, 0))
        return 1;
      continue;
    }
    if (memcmp(key,table->record[0]+key_part->offset,length))
      return 1;
  }
  return 0;
}

/*
  unpack key-fields from record to some buffer.

  This is used mainly to get a good error message.  We temporary 
  change the column bitmap so that all columns are readable.

  @param
     to		Store value here in an easy to read form
  @param
     table	Table to use
  @param
     idx	Key number
*/

void key_unpack(String *to,TABLE *table,uint idx)
{
  KEY_PART_INFO *key_part,*key_part_end;
  Field *field;
  String tmp;
  my_bitmap_map *old_map= dbug_tmp_use_all_columns(table, table->read_set);
  DBUG_ENTER("key_unpack");

  to->length(0);
  for (key_part=table->key_info[idx].key_part,key_part_end=key_part+
	 table->key_info[idx].key_parts ;
       key_part < key_part_end;
       key_part++)
  {
    if (to->length())
      to->append('-');
    if (key_part->null_bit)
    {
      if (table->record[0][key_part->null_offset] & key_part->null_bit)
      {
	to->append(STRING_WITH_LEN("NULL"));
	continue;
      }
    }
    if ((field=key_part->field))
    {
      CHARSET_INFO *cs= field->charset();
      field->val_str(&tmp);
      if (cs->mbmaxlen > 1 &&
          table->field[key_part->fieldnr - 1]->field_length !=
          key_part->length)
      {
        /*
          Prefix key, multi-byte charset.
          For the columns of type CHAR(N), the above val_str()
          call will return exactly "key_part->length" bytes,
          which can break a multi-byte characters in the middle.
          Align, returning not more than "char_length" characters.
        */
        uint charpos, char_length= key_part->length / cs->mbmaxlen;
        if ((charpos= my_charpos(cs, tmp.ptr(),
                                 tmp.ptr() + tmp.length(),
                                 char_length)) < key_part->length)
          tmp.length(charpos);
      }
      
      if (key_part->length < field->pack_length())
	tmp.length(min(tmp.length(),key_part->length));
      to->append(tmp);
    }
    else
      to->append(STRING_WITH_LEN("???"));
  }
  dbug_tmp_restore_column_map(table->read_set, old_map);
  DBUG_VOID_RETURN;
}


/*
  Check if key uses field that is marked in passed field bitmap.

  SYNOPSIS
    is_key_used()
      table   TABLE object with which keys and fields are associated.
      idx     Key to be checked.
      fields  Bitmap of fields to be checked.

  NOTE
    This function uses TABLE::tmp_set bitmap so the caller should care
    about saving/restoring its state if it also uses this bitmap.

  RETURN VALUE
    TRUE   Key uses field from bitmap
    FALSE  Otherwise
*/

bool is_key_used(TABLE *table, uint idx, const MY_BITMAP *fields)
{
  bitmap_clear_all(&table->tmp_set);
  table->mark_columns_used_by_index_no_reset(idx, &table->tmp_set);
  if (bitmap_is_overlapping(&table->tmp_set, fields))
    return 1;

  /*
    If table handler has primary key as part of the index, check that primary
    key is not updated
  */
  if (idx != table->s->primary_key && table->s->primary_key < MAX_KEY &&
      (table->file->ha_table_flags() & HA_PRIMARY_KEY_IN_READ_INDEX))
    return is_key_used(table, table->s->primary_key, fields);
  return 0;
}


/**
  Compare key in row to a given key.

  @param key_part		Key part handler
  @param key			Key to compare to value in table->record[0]
  @param key_length		length of 'key'

  @return
    The return value is SIGN(key_in_row - range_key):
    -   0		Key is equal to range or 'range' == 0 (no range)
    -  -1		Key is less than range
    -   1		Key is larger than range
*/

int key_cmp(KEY_PART_INFO *key_part, const uchar *key, uint key_length)
{
  uint store_length;

  for (const uchar *end=key + key_length;
       key < end;
       key+= store_length, key_part++)
  {
    int cmp;
    store_length= key_part->store_length;
    if (key_part->null_bit)
    {
      /* This key part allows null values; NULL is lower than everything */
      register bool field_is_null= key_part->field->is_null();
      if (*key)                                 // If range key is null
      {
	/* the range is expecting a null value */
	if (!field_is_null)
	  return 1;                             // Found key is > range
        /* null -- exact match, go to next key part */
	continue;
      }
      else if (field_is_null)
	return -1;                              // NULL is less than any value
      key++;					// Skip null byte
      store_length--;
    }
    if ((cmp=key_part->field->key_cmp(key, key_part->length)) < 0)
      return -1;
    if (cmp > 0)
      return 1;
  }
  return 0;                                     // Keys are equal
}


/*
  Compare two records in index order
  SYNOPSIS
    key_rec_cmp()
    key                         Index information
    rec0                        Pointer to table->record[0]
    first_rec                   Pointer to record compare with
    second_rec                  Pointer to record compare against first_rec

  DESCRIPTION
    This method is set-up such that it can be called directly from the
    priority queue and it is attempted to be optimised as much as possible
    since this will be called O(N * log N) times while performing a merge
    sort in various places in the code.

    We retrieve the pointer to table->record[0] using the fact that key_parts
    have an offset making it possible to calculate the start of the record.
    We need to get the diff to the compared record since none of the records
    being compared are stored in table->record[0].

    We first check for NULL values, if there are no NULL values we use
    a compare method that gets two field pointers and a max length
    and return the result of the comparison.
*/

int key_rec_cmp(void *key, uchar *first_rec, uchar *second_rec)
{
  KEY *key_info= (KEY*)key;
  uint key_parts= key_info->key_parts, i= 0;
  KEY_PART_INFO *key_part= key_info->key_part;
  uchar *rec0= key_part->field->ptr - key_part->offset;
  my_ptrdiff_t first_diff= first_rec - rec0, sec_diff= second_rec - rec0;
  int result= 0;
  DBUG_ENTER("key_rec_cmp");

  do
  {
    Field *field= key_part->field;

    if (key_part->null_bit)
    {
      /* The key_part can contain NULL values */
      bool first_is_null= field->is_null_in_record_with_offset(first_diff);
      bool sec_is_null= field->is_null_in_record_with_offset(sec_diff);
      /*
        NULL is smaller then everything so if first is NULL and the other
        not then we know that we should return -1 and for the opposite
        we should return +1. If both are NULL then we call it equality
        although it is a strange form of equality, we have equally little
        information of the real value.
      */
      if (!first_is_null)
      {
        if (!sec_is_null)
          ; /* Fall through, no NULL fields */
        else
        {
          DBUG_RETURN(+1);
        }
      }
      else if (!sec_is_null)
      {
        DBUG_RETURN(-1);
      }
      else
        goto next_loop; /* Both were NULL */
    }
    /*
      No null values in the fields
      We use the virtual method cmp_max with a max length parameter.
      For most field types this translates into a cmp without
      max length. The exceptions are the BLOB and VARCHAR field types
      that take the max length into account.
    */
    result= field->cmp_max(field->ptr+first_diff, field->ptr+sec_diff,
                           key_part->length);
next_loop:
    key_part++;
  } while (!result && ++i < key_parts);
  DBUG_RETURN(result);
}