path: root/sql/key.cc

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult 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; either version 2 of the License, or
   (at your option) any later version.

   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"
#include "sql_trigger.h"

	/*
	** Search after with key field is. If no key starts with field test
	** if field is part of some key.
	**
	** returns number of key. keylength is set to length of key before
	** (not including) field
	** Used when calculating key for NEXT_NUMBER
	*/

int find_ref_key(TABLE *table,Field *field, uint *key_length)
{
  reg2 int i;
  reg3 KEY *key_info;
  uint fieldpos;

  fieldpos=    field->offset();

	/* Test if some key starts as fieldpos */

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

  for (i= 0, key_info= table->key_info ;
       i < (int) table->s->keys ;
       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)
	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.

  SYNOPSIS
    key_copy()
    to_key      buffer that will be used as a key
    from_record full record to be copied from
    key_info    descriptor of the index
    key_length  specifies length of all keyparts that will be copied

  DESCRIPTION
    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.

  RETURN
    None
*/

void key_copy(byte *to_key, byte *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->type == HA_KEYTYPE_BIT)
    {
      Field_bit *field= (Field_bit *) (key_part->field);
      if (field->bit_len)
      {
        uchar bits= get_rec_bits((uchar*) from_record +
                                 key_part->null_offset +
                                 (key_part->null_bit == 128),
                                 field->bit_ofs, field->bit_len);
        *to_key++= bits;
        key_length--;
      }
    }
    if (key_part->key_part_flag & HA_BLOB_PART)
    {
      char *pos;
      ulong blob_length= ((Field_blob*) key_part->field)->get_length();
      key_length-= HA_KEY_BLOB_LENGTH;
      ((Field_blob*) key_part->field)->get_ptr(&pos);
      length=min(key_length, key_part->length);
      set_if_smaller(blob_length, length);
      int2store(to_key, (uint) blob_length);
      to_key+= HA_KEY_BLOB_LENGTH;			// Skip length info
      memcpy(to_key, pos, blob_length);
    }
    else if (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((char *) to_key, length, Field::itRAW);
      to_key+= HA_KEY_BLOB_LENGTH;
    }
    else
    {
      length= min(key_length, key_part->length);
      memcpy(to_key, from_record + key_part->offset, (size_t) length);
    }
    to_key+= length;
    key_length-= length;
  }
}


/*
  Restore a key from some buffer to record.

  SYNOPSIS
    key_restore()
    to_record   record buffer where the key will be restored to
    from_key    buffer that contains a key
    key_info    descriptor of the index
    key_length  specifies length of all keyparts that will be restored

  DESCRIPTION
    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.

  RETURN
    None
*/

void key_restore(byte *to_record, byte *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++)
  {
    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);
      }
    }
    if (key_part->key_part_flag & HA_BLOB_PART)
    {
      uint blob_length= uint2korr(from_key);
      from_key+= HA_KEY_BLOB_LENGTH;
      key_length-= HA_KEY_BLOB_LENGTH;
      ((Field_blob*) key_part->field)->set_ptr((ulong) blob_length,
					       (char*) from_key);
      length= key_part->length;
    }
    else if (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->set_key_image((char *) from_key, length);
      from_key+= HA_KEY_BLOB_LENGTH;
    }
    else
    {
      length= min(key_length, key_part->length);
      memcpy(to_record + key_part->offset, from_key, (size_t) length);
    }
    from_key+= length;
    key_length-= length;
  }
}


/*
  Compare if a key has changed

  SYNOPSIS
    key_cmp_if_same()
    table		TABLE
    key			key to compare to row
    idx			Index used
    key_length		Length of key

  NOTES
    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.

  RETURN
    0	If key is equal
    1	Key has changed
*/

bool key_cmp_if_same(TABLE *table,const byte *key,uint idx,uint key_length)
{
  uint store_length;
  KEY_PART_INFO *key_part;
  const byte *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 byte *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 to get a good error message */

void key_unpack(String *to,TABLE *table,uint idx)
{
  KEY_PART_INFO *key_part,*key_part_end;
  Field *field;
  String tmp;
  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))
    {
      field->val_str(&tmp);
      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_VOID_RETURN;
}


/*
  Check if key uses field that is listed in passed field list or is
  automatically updated (like a timestamp) or can be updated by before
  update trigger defined on the table.

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

  RETURN VALUE
    TRUE   Key uses field which meets one the above conditions
    FALSE  Otherwise
*/

bool is_key_used(TABLE *table, uint idx, List<Item> &fields)
{
  Table_triggers_list *triggers= table->triggers;
  List_iterator_fast<Item> f(fields);
  KEY_PART_INFO *key_part,*key_part_end;
  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++)
  {
    Item_field *field;

    if (key_part->field == table->timestamp_field)
      return 1;					// Can't be used for update

    f.rewind();
    while ((field=(Item_field*) f++))
    {
      if (key_part->field->eq(field->field))
	return 1;
    }
    if (triggers &&
        triggers->is_updated_in_before_update_triggers(key_part->field))
      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->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

  SYNOPSIS
    key_cmp()
    key_part		Key part handler
    key			Key to compare to value in table->record[0]
    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 byte *key, uint key_length)
{
  uint store_length;

  for (const byte *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((byte*) key, key_part->length)) < 0)
      return -1;
    if (cmp > 0)
      return 1;
  }
  return 0;                                     // Keys are equal
}