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; 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

  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, byte *record, Field *field,
                 uint *key_length)
{
  reg2 int i;
  reg3 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=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)
	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)
    {
      my_bitmap_map *old_map;
      key_length-= HA_KEY_BLOB_LENGTH;
      length= min(key_length, key_part->length);
      old_map= dbug_tmp_use_all_columns(key_part->field->table,
                                        key_part->field->table->write_set);
      key_part->field->set_key_image((char *) from_key, length);
      dbug_tmp_restore_column_map(key_part->field->table->write_set, old_map);
      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

  SYNOPSIS
     key_unpack()
     to		Store value here in an easy to read form
     table	Table to use
     idx	Key number

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

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))
    {
      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_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

  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
}


/*
  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, byte *first_rec, byte *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;
  char *rec0= key_part->field->ptr - key_part->offset;
  my_ptrdiff_t first_diff= first_rec - (byte*)rec0, sec_diff= second_rec - (byte*)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);
}