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

/**

  @file

  @brief

  Functions for easy reading of records, possible through a cache

*/

#include <drizzled/server_includes.h>

static int rr_quick(READ_RECORD *info);

int rr_sequential(READ_RECORD *info);

static int rr_from_tempfile(READ_RECORD *info);

static int rr_unpack_from_tempfile(READ_RECORD *info);

static int rr_unpack_from_buffer(READ_RECORD *info);

static int rr_from_pointers(READ_RECORD *info);

static int rr_from_cache(READ_RECORD *info);

static int init_rr_cache(THD *thd, READ_RECORD *info);

static int rr_cmp(uchar *a,uchar *b);

static int rr_index_first(READ_RECORD *info);

static int rr_index(READ_RECORD *info);

/**

  Initialize READ_RECORD structure to perform full index scan (in forward

  direction) using read_record.read_record() interface.

    This function has been added at late stage and is used only by

    UPDATE/DELETE. Other statements perform index scans using

    join_read_first/next functions.

  @param info         READ_RECORD structure to initialize.

  @param thd          Thread handle

  @param table        Table to be accessed

  @param print_error  If true, call table->file->print_error() if an error

                      occurs (except for end-of-records error)

  @param idx          index to scan

*/

void init_read_record_idx(READ_RECORD *info,

                          THD *thd __attribute__((unused)),

                          Table *table,

                          bool print_error, uint idx)

{

  empty_record(table);

  memset(info, 0, sizeof(*info));

  info->table= table;

  info->file=  table->file;

  info->record= table->record[0];

  info->print_error= print_error;

  table->status=0;			/* And it's always found */

  if (!table->file->inited)

    table->file->ha_index_init(idx, 1);

  /* read_record will be changed to rr_index in rr_index_first */

  info->read_record= rr_index_first;

}

/*

  init_read_record is used to scan by using a number of different methods.

  Which method to use is set-up in this call so that later calls to

  the info->read_record will call the appropriate method using a function

  pointer.

  There are five methods that relate completely to the sort function

  filesort. The result of a filesort is retrieved using read_record

  calls. The other two methods are used for normal table access.

  The filesort will produce references to the records sorted, these

  references can be stored in memory or in a temporary file.

  The temporary file is normally used when the references doesn't fit into

  a properly sized memory buffer. For most small queries the references

  are stored in the memory buffer.

  The temporary file is also used when performing an update where a key is

  modified.

  Methods used when ref's are in memory (using rr_from_pointers):

    rr_unpack_from_buffer:

    ----------------------

      This method is used when table->sort.addon_field is allocated.

      This is allocated for most SELECT queries not involving any BLOB's.

      In this case the records are fetched from a memory buffer.

    rr_from_pointers:

    -----------------

      Used when the above is not true, UPDATE, DELETE and so forth and

      SELECT's involving BLOB's. It is also used when the addon_field

      buffer is not allocated due to that its size was bigger than the

      session variable max_length_for_sort_data.

      In this case the record data is fetched from the handler using the

      saved reference using the rnd_pos handler call.

  Methods used when ref's are in a temporary file (using rr_from_tempfile)

    rr_unpack_from_tempfile:

    ------------------------

      Same as rr_unpack_from_buffer except that references are fetched from

      temporary file. Should obviously not really happen other than in

      strange configurations.

    rr_from_tempfile:

    -----------------

      Same as rr_from_pointers except that references are fetched from

      temporary file instead of from 

    rr_from_cache:

    --------------

      This is a special variant of rr_from_tempfile that can be used for

      handlers that is not using the HA_FAST_KEY_READ table flag. Instead

      of reading the references one by one from the temporary file it reads

      a set of them, sorts them and reads all of them into a buffer which

      is then used for a number of subsequent calls to rr_from_cache.

      It is only used for SELECT queries and a number of other conditions

      on table size.

  All other accesses use either index access methods (rr_quick) or a full

  table scan (rr_sequential).

  rr_quick:

  ---------

    rr_quick uses one of the QUICK_SELECT classes in opt_range.cc to

    perform an index scan. There are loads of functionality hidden

    in these quick classes. It handles all index scans of various kinds.

  rr_sequential:

  --------------

    This is the most basic access method of a table using rnd_init,

    rnd_next and rnd_end. No indexes are used.

*/

void init_read_record(READ_RECORD *info,THD *thd, Table *table,

		      SQL_SELECT *select,

		      int use_record_cache, bool print_error)

{

  IO_CACHE *tempfile;

  memset(info, 0, sizeof(*info));

  info->thd=thd;

  info->table=table;

  info->file= table->file;

  info->forms= &info->table;		/* Only one table */

  if (table->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE &&

      !table->sort.addon_field)

    VOID(table->file->extra(HA_EXTRA_MMAP));

  if (table->sort.addon_field)

  {

    info->rec_buf= table->sort.addon_buf;

    info->ref_length= table->sort.addon_length;

  }

  else

  {

    empty_record(table);

    info->record= table->record[0];

    info->ref_length= table->file->ref_length;

  }

  info->select=select;

  info->print_error=print_error;

  info->ignore_not_found_rows= 0;

  table->status=0;			/* And it's always found */

  if (select && my_b_inited(&select->file))

    tempfile= &select->file;

  else

    tempfile= table->sort.io_cache;

  if (tempfile && my_b_inited(tempfile)) // Test if ref-records was used

  {

    info->read_record= (table->sort.addon_field ?

                        rr_unpack_from_tempfile : rr_from_tempfile);

    info->io_cache=tempfile;

    reinit_io_cache(info->io_cache,READ_CACHE,0L,0,0);

    info->ref_pos=table->file->ref;

    if (!table->file->inited)

      table->file->ha_rnd_init(0);

    /*

      table->sort.addon_field is checked because if we use addon fields,

      it doesn't make sense to use cache - we don't read from the table

      and table->sort.io_cache is read sequentially

    */

    if (!table->sort.addon_field &&

	thd->variables.read_rnd_buff_size &&

	!(table->file->ha_table_flags() & HA_FAST_KEY_READ) &&

	(table->db_stat & HA_READ_ONLY ||

	 table->reginfo.lock_type <= TL_READ_NO_INSERT) &&

	(uint64_t) table->s->reclength* (table->file->stats.records+

                                          table->file->stats.deleted) >

	(uint64_t) MIN_FILE_LENGTH_TO_USE_ROW_CACHE &&

	info->io_cache->end_of_file/info->ref_length * table->s->reclength >

	(my_off_t) MIN_ROWS_TO_USE_TABLE_CACHE &&

	!table->s->blob_fields &&

        info->ref_length <= MAX_REFLENGTH)

    {

      if (! init_rr_cache(thd, info))

      {

	info->read_record=rr_from_cache;

      }

    }

  }

  else if (select && select->quick)

  {

    info->read_record=rr_quick;

  }

  else if (table->sort.record_pointers)

  {

    table->file->ha_rnd_init(0);

    info->cache_pos=table->sort.record_pointers;

    info->cache_end=info->cache_pos+ 

                    table->sort.found_records*info->ref_length;

    info->read_record= (table->sort.addon_field ?

                        rr_unpack_from_buffer : rr_from_pointers);

  }

  else

  {

    info->read_record=rr_sequential;

    table->file->ha_rnd_init(1);

    /* We can use record cache if we don't update dynamic length tables */

    if (!table->no_cache &&

	(use_record_cache > 0 ||

	 (int) table->reginfo.lock_type <= (int) TL_READ_HIGH_PRIORITY ||

	 !(table->s->db_options_in_use & HA_OPTION_PACK_RECORD) ||

	 (use_record_cache < 0 &&

	  !(table->file->ha_table_flags() & HA_NOT_DELETE_WITH_CACHE))))

      VOID(table->file->extra_opt(HA_EXTRA_CACHE,

				  thd->variables.read_buff_size));

  }

  /* 

    Do condition pushdown for UPDATE/DELETE.

    TODO: Remove this from here as it causes two condition pushdown calls 

    when we're running a SELECT and the condition cannot be pushed down.

  */

  if (thd->variables.engine_condition_pushdown && 

      select && select->cond && 

      (select->cond->used_tables() & table->map) &&

      !table->file->pushed_cond)

    table->file->cond_push(select->cond);

  return;

} /* init_read_record */

void end_read_record(READ_RECORD *info)

{                   /* free cache if used */

  if (info->cache)

  {

    my_free_lock((char*) info->cache,MYF(0));

    info->cache=0;

  }

  if (info->table)

  {

    filesort_free_buffers(info->table,0);

    (void) info->file->extra(HA_EXTRA_NO_CACHE);

    if (info->read_record != rr_quick) // otherwise quick_range does it

      (void) info->file->ha_index_or_rnd_end();

    info->table=0;

  }

}

static int rr_handle_error(READ_RECORD *info, int error)

{

  if (error == HA_ERR_END_OF_FILE)

    error= -1;

  else

  {

    if (info->print_error)

      info->table->file->print_error(error, MYF(0));

    if (error < 0)                            // Fix negative BDB errno

      error= 1;

  }

  return error;

}

/** Read a record from head-database. */

static int rr_quick(READ_RECORD *info)

{

  int tmp;

  while ((tmp= info->select->quick->get_next()))

  {

    if (info->thd->killed)

    {

      my_error(ER_SERVER_SHUTDOWN, MYF(0));

      return 1;

    }

    if (tmp != HA_ERR_RECORD_DELETED)

    {

      tmp= rr_handle_error(info, tmp);

      break;

    }

  }

  return tmp;

}

/**

  Reads first row in an index scan.

  @param info  	Scan info

  @retval

    0   Ok

  @retval

    -1   End of records

  @retval

    1   Error

*/

static int rr_index_first(READ_RECORD *info)

{

  int tmp= info->file->index_first(info->record);

  info->read_record= rr_index;

  if (tmp)

    tmp= rr_handle_error(info, tmp);

  return tmp;

}

/**

  Reads index sequentially after first row.

  Read the next index record (in forward direction) and translate return

  value.

  @param info  Scan info

  @retval

    0   Ok

  @retval

    -1   End of records

  @retval

    1   Error

*/

static int rr_index(READ_RECORD *info)

{

  int tmp= info->file->index_next(info->record);

  if (tmp)

    tmp= rr_handle_error(info, tmp);

  return tmp;

}

int rr_sequential(READ_RECORD *info)

{

  int tmp;

  while ((tmp=info->file->rnd_next(info->record)))

  {

    if (info->thd->killed)

    {

      info->thd->send_kill_message();

      return 1;

    }

    /*

      rnd_next can return RECORD_DELETED for MyISAM when one thread is

      reading and another deleting without locks.

    */

    if (tmp != HA_ERR_RECORD_DELETED)

    {

      tmp= rr_handle_error(info, tmp);

      break;

    }

  }

  return tmp;

}

static int rr_from_tempfile(READ_RECORD *info)

{

  int tmp;

  for (;;)

  {

    if (my_b_read(info->io_cache,info->ref_pos,info->ref_length))

      return -1;					/* End of file */

    if (!(tmp=info->file->rnd_pos(info->record,info->ref_pos)))

      break;

    /* The following is extremely unlikely to happen */

    if (tmp == HA_ERR_RECORD_DELETED ||

        (tmp == HA_ERR_KEY_NOT_FOUND && info->ignore_not_found_rows))

      continue;

    tmp= rr_handle_error(info, tmp);

    break;

  }

  return tmp;

} /* rr_from_tempfile */

/**

  Read a result set record from a temporary file after sorting.

  The function first reads the next sorted record from the temporary file.

  into a buffer. If a success it calls a callback function that unpacks 

  the fields values use in the result set from this buffer into their

  positions in the regular record buffer.

  @param info          Reference to the context including record descriptors

  @retval

    0   Record successfully read.

  @retval

    -1   There is no record to be read anymore.

*/

static int rr_unpack_from_tempfile(READ_RECORD *info)

{

  if (my_b_read(info->io_cache, info->rec_buf, info->ref_length))

    return -1;

  Table *table= info->table;

  (*table->sort.unpack)(table->sort.addon_field, info->rec_buf);

  return 0;

}

static int rr_from_pointers(READ_RECORD *info)

{

  int tmp;

  uchar *cache_pos;

  for (;;)

  {

    if (info->cache_pos == info->cache_end)

      return -1;					/* End of file */

    cache_pos= info->cache_pos;

    info->cache_pos+= info->ref_length;

    if (!(tmp=info->file->rnd_pos(info->record,cache_pos)))

      break;

    /* The following is extremely unlikely to happen */

    if (tmp == HA_ERR_RECORD_DELETED ||

        (tmp == HA_ERR_KEY_NOT_FOUND && info->ignore_not_found_rows))

      continue;

    tmp= rr_handle_error(info, tmp);

    break;

  }

  return tmp;

}

/**

  Read a result set record from a buffer after sorting.

  The function first reads the next sorted record from the sort buffer.

  If a success it calls a callback function that unpacks 

  the fields values use in the result set from this buffer into their

  positions in the regular record buffer.

  @param info          Reference to the context including record descriptors

  @retval

    0   Record successfully read.

  @retval

    -1   There is no record to be read anymore.

*/

static int rr_unpack_from_buffer(READ_RECORD *info)

{

  if (info->cache_pos == info->cache_end)

    return -1;                      /* End of buffer */

  Table *table= info->table;

  (*table->sort.unpack)(table->sort.addon_field, info->cache_pos);

  info->cache_pos+= info->ref_length;

  return 0;

}

	/* cacheing of records from a database */

static int init_rr_cache(THD *thd, READ_RECORD *info)

{

  uint rec_cache_size;

  info->struct_length= 3+MAX_REFLENGTH;

  info->reclength= ALIGN_SIZE(info->table->s->reclength+1);

  if (info->reclength < info->struct_length)

    info->reclength= ALIGN_SIZE(info->struct_length);

  info->error_offset= info->table->s->reclength;

  info->cache_records= (thd->variables.read_rnd_buff_size /

                        (info->reclength+info->struct_length));

  rec_cache_size= info->cache_records*info->reclength;

  info->rec_cache_size= info->cache_records*info->ref_length;

  // We have to allocate one more byte to use uint3korr (see comments for it)

  if (info->cache_records <= 2 ||

      !(info->cache=(uchar*) my_malloc_lock(rec_cache_size+info->cache_records*

					   info->struct_length+1,

					   MYF(0))))

    return(1);

#ifdef HAVE_purify

  // Avoid warnings in qsort

  memset(info->cache, 0,

         rec_cache_size+info->cache_records* info->struct_length+1);

#endif

  info->read_positions=info->cache+rec_cache_size;

  info->cache_pos=info->cache_end=info->cache;

  return(0);

} /* init_rr_cache */

static int rr_from_cache(READ_RECORD *info)

{

  register uint i;

  uint32_t length;

  my_off_t rest_of_file;

  int16_t error;

  uchar *position,*ref_position,*record_pos;

  uint32_t record;

  for (;;)

  {

    if (info->cache_pos != info->cache_end)

    {

      if (info->cache_pos[info->error_offset])

      {

	shortget(error,info->cache_pos);

	if (info->print_error)

	  info->table->file->print_error(error,MYF(0));

      }

      else

      {

	error=0;

	memcpy(info->record,info->cache_pos,

               (size_t) info->table->s->reclength);

      }

      info->cache_pos+=info->reclength;

      return ((int) error);

    }

    length=info->rec_cache_size;

    rest_of_file=info->io_cache->end_of_file - my_b_tell(info->io_cache);

    if ((my_off_t) length > rest_of_file)

      length= (uint32_t) rest_of_file;

    if (!length || my_b_read(info->io_cache,info->cache,length))

    {

      return -1;			/* End of file */

    }

    length/=info->ref_length;

    position=info->cache;

    ref_position=info->read_positions;

    for (i=0 ; i < length ; i++,position+=info->ref_length)

    {

      memcpy(ref_position,position,(size_t) info->ref_length);

      ref_position+=MAX_REFLENGTH;

      int3store(ref_position,(long) i);

      ref_position+=3;

    }

    my_qsort(info->read_positions, length, info->struct_length,

             (qsort_cmp) rr_cmp);

    position=info->read_positions;

    for (i=0 ; i < length ; i++)

    {

      memcpy(info->ref_pos,position,(size_t) info->ref_length);

      position+=MAX_REFLENGTH;

      record=uint3korr(position);

      position+=3;

      record_pos=info->cache+record*info->reclength;

      if ((error=(int16_t) info->file->rnd_pos(record_pos,info->ref_pos)))

      {

	record_pos[info->error_offset]=1;

	shortstore(record_pos,error);

      }

      else

	record_pos[info->error_offset]=0;

    }

    info->cache_end=(info->cache_pos=info->cache)+length*info->reclength;

  }

} /* rr_from_cache */

static int rr_cmp(uchar *a,uchar *b)

{

  if (a[0] != b[0])

    return (int) a[0] - (int) b[0];

  if (a[1] != b[1])

    return (int) a[1] - (int) b[1];

  if (a[2] != b[2])

    return (int) a[2] - (int) b[2];

#if MAX_REFLENGTH == 4

  return (int) a[3] - (int) b[3];

#else

  if (a[3] != b[3])

    return (int) a[3] - (int) b[3];

  if (a[4] != b[4])

    return (int) a[4] - (int) b[4];

  if (a[5] != b[5])

    return (int) a[1] - (int) b[5];

  if (a[6] != b[6])

    return (int) a[6] - (int) b[6];

  return (int) a[7] - (int) b[7];

#endif

}