~drizzle-trunk/drizzle/development

/* Copyright (C) 2001 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 */

/*

  Function to handle quick removal of duplicates

  This code is used when doing multi-table deletes to find the rows in

  reference tables that needs to be deleted.

  The basic idea is as follows:

  Store first all strings in a binary tree, ignoring duplicates.

  When the tree uses more memory than 'max_heap_table_size',

  write the tree (in sorted order) out to disk and start with a new tree.

  When all data has been generated, merge the trees (removing any found

  duplicates).

  The unique entries will be returned in sort order, to ensure that we do the

  deletes in disk order.

*/

#include "mysql_priv.h"

#include "sql_sort.h"

int unique_write_to_file(uchar* key, element_count count, Unique *unique)

{

  /*

    Use unique->size (size of element stored in the tree) and not

    unique->tree.size_of_element. The latter is different from unique->size

    when tree implementation chooses to store pointer to key in TREE_ELEMENT

    (instead of storing the element itself there)

  */

  return my_b_write(&unique->file, key, unique->size) ? 1 : 0;

}

int unique_write_to_ptrs(uchar* key, element_count count, Unique *unique)

{

  memcpy(unique->record_pointers, key, unique->size);

  unique->record_pointers+=unique->size;

  return 0;

}

Unique::Unique(qsort_cmp2 comp_func, void * comp_func_fixed_arg,

	       uint size_arg, ulonglong max_in_memory_size_arg)

  :max_in_memory_size(max_in_memory_size_arg), size(size_arg), elements(0)

{

  my_b_clear(&file);

  init_tree(&tree, (ulong) (max_in_memory_size / 16), 0, size, comp_func, 0,

            NULL, comp_func_fixed_arg);

  /* If the following fail's the next add will also fail */

  my_init_dynamic_array(&file_ptrs, sizeof(BUFFPEK), 16, 16);

  /*

    If you change the following, change it in get_max_elements function, too.

  */

  max_elements= (ulong) (max_in_memory_size /

                         ALIGN_SIZE(sizeof(TREE_ELEMENT)+size));

  VOID(open_cached_file(&file, mysql_tmpdir,TEMP_PREFIX, DISK_BUFFER_SIZE,

		   MYF(MY_WME)));

}

/*

  Calculate log2(n!)

  NOTES

    Stirling's approximate formula is used:

      n! ~= sqrt(2*M_PI*n) * (n/M_E)^n

    Derivation of formula used for calculations is as follows:

    log2(n!) = log(n!)/log(2) = log(sqrt(2*M_PI*n)*(n/M_E)^n) / log(2) =

      = (log(2*M_PI*n)/2 + n*log(n/M_E)) / log(2).

*/

inline double log2_n_fact(double x)

{

  return (log(2*M_PI*x)/2 + x*log(x/M_E)) / M_LN2;

}

/*

  Calculate cost of merge_buffers function call for given sequence of

  input stream lengths and store the number of rows in result stream in *last.

  SYNOPSIS

    get_merge_buffers_cost()

      buff_elems  Array of #s of elements in buffers

      elem_size   Size of element stored in buffer

      first       Pointer to first merged element size

      last        Pointer to last merged element size

  RETURN

    Cost of merge_buffers operation in disk seeks.

  NOTES

    It is assumed that no rows are eliminated during merge.

    The cost is calculated as

      cost(read_and_write) + cost(merge_comparisons).

    All bytes in the sequences is read and written back during merge so cost

    of disk io is 2*elem_size*total_buf_elems/IO_SIZE (2 is for read + write)

    For comparisons cost calculations we assume that all merged sequences have

    the same length, so each of total_buf_size elements will be added to a sort

    heap with (n_buffers-1) elements. This gives the comparison cost:

      total_buf_elems* log2(n_buffers) / TIME_FOR_COMPARE_ROWID;

*/

static double get_merge_buffers_cost(uint *buff_elems, uint elem_size,

                                     uint *first, uint *last)

{

  uint total_buf_elems= 0;

  for (uint *pbuf= first; pbuf <= last; pbuf++)

    total_buf_elems+= *pbuf;

  *last= total_buf_elems;

  int n_buffers= last - first + 1;

  /* Using log2(n)=log(n)/log(2) formula */

  return 2*((double)total_buf_elems*elem_size) / IO_SIZE +

     total_buf_elems*log((double) n_buffers) / (TIME_FOR_COMPARE_ROWID * M_LN2);

}

/*

  Calculate cost of merging buffers into one in Unique::get, i.e. calculate

  how long (in terms of disk seeks) the two calls

    merge_many_buffs(...);

    merge_buffers(...);

  will take.

  SYNOPSIS

    get_merge_many_buffs_cost()

      buffer        buffer space for temporary data, at least

                    Unique::get_cost_calc_buff_size bytes

      maxbuffer     # of full buffers

      max_n_elems   # of elements in first maxbuffer buffers

      last_n_elems  # of elements in last buffer

      elem_size     size of buffer element

  NOTES

    maxbuffer+1 buffers are merged, where first maxbuffer buffers contain

    max_n_elems elements each and last buffer contains last_n_elems elements.

    The current implementation does a dumb simulation of merge_many_buffs

    function actions.

  RETURN

    Cost of merge in disk seeks.

*/

static double get_merge_many_buffs_cost(uint *buffer,

                                        uint maxbuffer, uint max_n_elems,

                                        uint last_n_elems, int elem_size)

{

  register int i;

  double total_cost= 0.0;

  uint *buff_elems= buffer; /* #s of elements in each of merged sequences */

  /*

    Set initial state: first maxbuffer sequences contain max_n_elems elements

    each, last sequence contains last_n_elems elements.

  */

  for (i = 0; i < (int)maxbuffer; i++)

    buff_elems[i]= max_n_elems;

  buff_elems[maxbuffer]= last_n_elems;

  /*

    Do it exactly as merge_many_buff function does, calling

    get_merge_buffers_cost to get cost of merge_buffers.

  */

  if (maxbuffer >= MERGEBUFF2)

  {

    while (maxbuffer >= MERGEBUFF2)

    {

      uint lastbuff= 0;

      for (i = 0; i <= (int) maxbuffer - MERGEBUFF*3/2; i += MERGEBUFF)

      {

        total_cost+=get_merge_buffers_cost(buff_elems, elem_size,

                                           buff_elems + i,

                                           buff_elems + i + MERGEBUFF-1);

	lastbuff++;

      }

      total_cost+=get_merge_buffers_cost(buff_elems, elem_size,

                                         buff_elems + i,

                                         buff_elems + maxbuffer);

      maxbuffer= lastbuff;

    }

  }

  /* Simulate final merge_buff call. */

  total_cost += get_merge_buffers_cost(buff_elems, elem_size,

                                       buff_elems, buff_elems + maxbuffer);

  return total_cost;

}

/*

  Calculate cost of using Unique for processing nkeys elements of size

  key_size using max_in_memory_size memory.

  SYNOPSIS

    Unique::get_use_cost()

      buffer    space for temporary data, use Unique::get_cost_calc_buff_size

                to get # bytes needed.

      nkeys     #of elements in Unique

      key_size  size of each elements in bytes

      max_in_memory_size amount of memory Unique will be allowed to use

  RETURN

    Cost in disk seeks.

  NOTES

    cost(using_unqiue) =

      cost(create_trees) +  (see #1)

      cost(merge) +         (see #2)

      cost(read_result)     (see #3)

    1. Cost of trees creation

      For each Unique::put operation there will be 2*log2(n+1) elements

      comparisons, where n runs from 1 tree_size (we assume that all added

      elements are different). Together this gives:

      n_compares = 2*(log2(2) + log2(3) + ... + log2(N+1)) = 2*log2((N+1)!)

      then cost(tree_creation) = n_compares*ROWID_COMPARE_COST;

      Total cost of creating trees:

      (n_trees - 1)*max_size_tree_cost + non_max_size_tree_cost.

      Approximate value of log2(N!) is calculated by log2_n_fact function.

    2. Cost of merging.

      If only one tree is created by Unique no merging will be necessary.

      Otherwise, we model execution of merge_many_buff function and count

      #of merges. (The reason behind this is that number of buffers is small,

      while size of buffers is big and we don't want to loose precision with

      O(x)-style formula)

    3. If only one tree is created by Unique no disk io will happen.

      Otherwise, ceil(key_len*n_keys) disk seeks are necessary. We assume

      these will be random seeks.

*/

double Unique::get_use_cost(uint *buffer, uint nkeys, uint key_size,

                            ulonglong max_in_memory_size)

{

  ulong max_elements_in_tree;

  ulong last_tree_elems;

  int   n_full_trees; /* number of trees in unique - 1 */

  double result;

  max_elements_in_tree= ((ulong) max_in_memory_size /

                         ALIGN_SIZE(sizeof(TREE_ELEMENT)+key_size));

  n_full_trees=    nkeys / max_elements_in_tree;

  last_tree_elems= nkeys % max_elements_in_tree;

  /* Calculate cost of creating trees */

  result= 2*log2_n_fact(last_tree_elems + 1.0);

  if (n_full_trees)

    result+= n_full_trees * log2_n_fact(max_elements_in_tree + 1.0);

  result /= TIME_FOR_COMPARE_ROWID;

  if (!n_full_trees)

    return result;

  /*

    There is more then one tree and merging is necessary.

    First, add cost of writing all trees to disk, assuming that all disk

    writes are sequential.

  */

  result += DISK_SEEK_BASE_COST * n_full_trees *

              ceil(((double) key_size)*max_elements_in_tree / IO_SIZE);

  result += DISK_SEEK_BASE_COST * ceil(((double) key_size)*last_tree_elems / IO_SIZE);

  /* Cost of merge */

  double merge_cost= get_merge_many_buffs_cost(buffer, n_full_trees,

                                               max_elements_in_tree,

                                               last_tree_elems, key_size);

  if (merge_cost < 0.0)

    return merge_cost;

  result += merge_cost;

  /*

    Add cost of reading the resulting sequence, assuming there were no

    duplicate elements.

  */

  result += ceil((double)key_size*nkeys/IO_SIZE);

  return result;

}

Unique::~Unique()

{

  close_cached_file(&file);

  delete_tree(&tree);

  delete_dynamic(&file_ptrs);

}

    /* Write tree to disk; clear tree */

bool Unique::flush()

{

  BUFFPEK file_ptr;

  elements+= tree.elements_in_tree;

  file_ptr.count=tree.elements_in_tree;

  file_ptr.file_pos=my_b_tell(&file);

  if (tree_walk(&tree, (tree_walk_action) unique_write_to_file,

		(void*) this, left_root_right) ||

      insert_dynamic(&file_ptrs, (uchar*) &file_ptr))

    return 1;

  delete_tree(&tree);

  return 0;

}

/*

  Clear the tree and the file.

  You must call reset() if you want to reuse Unique after walk().

*/

void

Unique::reset()

{

  reset_tree(&tree);

  /*

    If elements != 0, some trees were stored in the file (see how

    flush() works). Note, that we can not count on my_b_tell(&file) == 0

    here, because it can return 0 right after walk(), and walk() does not

    reset any Unique member.

  */

  if (elements)

  {

    reset_dynamic(&file_ptrs);

    reinit_io_cache(&file, WRITE_CACHE, 0L, 0, 1);

  }

  elements= 0;

}

/*

  The comparison function, passed to queue_init() in merge_walk() and in

  merge_buffers() when the latter is called from Uniques::get() must

  use comparison function of Uniques::tree, but compare members of struct

  BUFFPEK.

*/

C_MODE_START

static int buffpek_compare(void *arg, uchar *key_ptr1, uchar *key_ptr2)

{

  BUFFPEK_COMPARE_CONTEXT *ctx= (BUFFPEK_COMPARE_CONTEXT *) arg;

  return ctx->key_compare(ctx->key_compare_arg,

                          *((uchar **) key_ptr1), *((uchar **)key_ptr2));

}

C_MODE_END

/*

  DESCRIPTION

    Function is very similar to merge_buffers, but instead of writing sorted

    unique keys to the output file, it invokes walk_action for each key.

    This saves I/O if you need to pass through all unique keys only once.

  SYNOPSIS

    merge_walk()

  All params are 'IN' (but see comment for begin, end):

    merge_buffer       buffer to perform cached piece-by-piece loading

                       of trees; initially the buffer is empty

    merge_buffer_size  size of merge_buffer. Must be aligned with

                       key_length

    key_length         size of tree element; key_length * (end - begin)

                       must be less or equal than merge_buffer_size.

    begin              pointer to BUFFPEK struct for the first tree.

    end                pointer to BUFFPEK struct for the last tree;

                       end > begin and [begin, end) form a consecutive

                       range. BUFFPEKs structs in that range are used and

                       overwritten in merge_walk().

    walk_action        element visitor. Action is called for each unique

                       key.

    walk_action_arg    argument to walk action. Passed to it on each call.

    compare            elements comparison function

    compare_arg        comparison function argument

    file               file with all trees dumped. Trees in the file

                       must contain sorted unique values. Cache must be

                       initialized in read mode.

  RETURN VALUE

    0     ok

    <> 0  error

*/

static bool merge_walk(uchar *merge_buffer, ulong merge_buffer_size,

                       uint key_length, BUFFPEK *begin, BUFFPEK *end,

                       tree_walk_action walk_action, void *walk_action_arg,

                       qsort_cmp2 compare, void *compare_arg,

                       IO_CACHE *file)

{

  BUFFPEK_COMPARE_CONTEXT compare_context = { compare, compare_arg };

  QUEUE queue;

  if (end <= begin ||

      merge_buffer_size < (ulong) (key_length * (end - begin + 1)) ||

      init_queue(&queue, (uint) (end - begin), offsetof(BUFFPEK, key), 0,

                 buffpek_compare, &compare_context))

    return 1;

  /* we need space for one key when a piece of merge buffer is re-read */

  merge_buffer_size-= key_length;

  uchar *save_key_buff= merge_buffer + merge_buffer_size;

  uint max_key_count_per_piece= (uint) (merge_buffer_size/(end-begin) /

                                        key_length);

  /* if piece_size is aligned reuse_freed_buffer will always hit */

  uint piece_size= max_key_count_per_piece * key_length;

  uint bytes_read;               /* to hold return value of read_to_buffer */

  BUFFPEK *top;

  int res= 1;

  /*

    Invariant: queue must contain top element from each tree, until a tree

    is not completely walked through.

    Here we're forcing the invariant, inserting one element from each tree

    to the queue.

  */

  for (top= begin; top != end; ++top)

  {

    top->base= merge_buffer + (top - begin) * piece_size;

    top->max_keys= max_key_count_per_piece;

    bytes_read= read_to_buffer(file, top, key_length);

    if (bytes_read == (uint) (-1))

      goto end;

    DBUG_ASSERT(bytes_read);

    queue_insert(&queue, (uchar *) top);

  }

  top= (BUFFPEK *) queue_top(&queue);

  while (queue.elements > 1)

  {

    /*

      Every iteration one element is removed from the queue, and one is

      inserted by the rules of the invariant. If two adjacent elements on

      the top of the queue are not equal, biggest one is unique, because all

      elements in each tree are unique. Action is applied only to unique

      elements.

    */

    void *old_key= top->key;

    /*

      read next key from the cache or from the file and push it to the

      queue; this gives new top.

    */

    top->key+= key_length;

    if (--top->mem_count)

      queue_replaced(&queue);

    else /* next piece should be read */

    {

      /* save old_key not to overwrite it in read_to_buffer */

      memcpy(save_key_buff, old_key, key_length);

      old_key= save_key_buff;

      bytes_read= read_to_buffer(file, top, key_length);

      if (bytes_read == (uint) (-1))

        goto end;

      else if (bytes_read > 0)      /* top->key, top->mem_count are reset */

        queue_replaced(&queue);     /* in read_to_buffer */

      else

      {

        /*

          Tree for old 'top' element is empty: remove it from the queue and

          give all its memory to the nearest tree.

        */

        queue_remove(&queue, 0);

        reuse_freed_buff(&queue, top, key_length);

      }

    }

    top= (BUFFPEK *) queue_top(&queue);

    /* new top has been obtained; if old top is unique, apply the action */

    if (compare(compare_arg, old_key, top->key))

    {

      if (walk_action(old_key, 1, walk_action_arg))

        goto end;

    }

  }

  /*

    Applying walk_action to the tail of the last tree: this is safe because

    either we had only one tree in the beginning, either we work with the

    last tree in the queue.

  */

  do

  {

    do

    {

      if (walk_action(top->key, 1, walk_action_arg))

        goto end;

      top->key+= key_length;

    }

    while (--top->mem_count);

    bytes_read= read_to_buffer(file, top, key_length);

    if (bytes_read == (uint) (-1))

      goto end;

  }

  while (bytes_read);

  res= 0;

end:

  delete_queue(&queue);

  return res;

}

/*

  DESCRIPTION

    Walks consecutively through all unique elements:

    if all elements are in memory, then it simply invokes 'tree_walk', else

    all flushed trees are loaded to memory piece-by-piece, pieces are

    sorted, and action is called for each unique value.

    Note: so as merging resets file_ptrs state, this method can change

    internal Unique state to undefined: if you want to reuse Unique after

    walk() you must call reset() first!

  SYNOPSIS

    Unique:walk()

  All params are 'IN':

    action  function-visitor, typed in include/my_tree.h

            function is called for each unique element

    arg     argument for visitor, which is passed to it on each call

  RETURN VALUE

    0    OK

    <> 0 error

 */

bool Unique::walk(tree_walk_action action, void *walk_action_arg)

{

  int res;

  uchar *merge_buffer;

  if (elements == 0)                       /* the whole tree is in memory */

    return tree_walk(&tree, action, walk_action_arg, left_root_right);

  /* flush current tree to the file to have some memory for merge buffer */

  if (flush())

    return 1;

  if (flush_io_cache(&file) || reinit_io_cache(&file, READ_CACHE, 0L, 0, 0))

    return 1;

  if (!(merge_buffer= (uchar *) my_malloc((ulong) max_in_memory_size, MYF(0))))

    return 1;

  res= merge_walk(merge_buffer, (ulong) max_in_memory_size, size,

                  (BUFFPEK *) file_ptrs.buffer,

                  (BUFFPEK *) file_ptrs.buffer + file_ptrs.elements,

                  action, walk_action_arg,

                  tree.compare, tree.custom_arg, &file);

  my_free((char*) merge_buffer, MYF(0));

  return res;

}

/*

  Modify the TABLE element so that when one calls init_records()

  the rows will be read in priority order.

*/

bool Unique::get(TABLE *table)

{

  SORTPARAM sort_param;

  table->sort.found_records=elements+tree.elements_in_tree;

  if (my_b_tell(&file) == 0)

  {

    /* Whole tree is in memory;  Don't use disk if you don't need to */

    if ((record_pointers=table->sort.record_pointers= (uchar*)

	 my_malloc(size * tree.elements_in_tree, MYF(0))))

    {

      (void) tree_walk(&tree, (tree_walk_action) unique_write_to_ptrs,

		       this, left_root_right);

      return 0;

    }

  }

  /* Not enough memory; Save the result to file && free memory used by tree */

  if (flush())

    return 1;

  IO_CACHE *outfile=table->sort.io_cache;

  BUFFPEK *file_ptr= (BUFFPEK*) file_ptrs.buffer;

  uint maxbuffer= file_ptrs.elements - 1;

  uchar *sort_buffer;

  my_off_t save_pos;

  bool error=1;

      /* Open cached file if it isn't open */

  outfile=table->sort.io_cache=(IO_CACHE*) my_malloc(sizeof(IO_CACHE),

                                MYF(MY_ZEROFILL));

  if (!outfile || (! my_b_inited(outfile) && open_cached_file(outfile,mysql_tmpdir,TEMP_PREFIX,READ_RECORD_BUFFER, MYF(MY_WME))))

    return 1;

  reinit_io_cache(outfile,WRITE_CACHE,0L,0,0);

  bzero((char*) &sort_param,sizeof(sort_param));

  sort_param.max_rows= elements;

  sort_param.sort_form=table;

  sort_param.rec_length= sort_param.sort_length= sort_param.ref_length=

    size;

  sort_param.keys= (uint) (max_in_memory_size / sort_param.sort_length);

  sort_param.not_killable=1;

  if (!(sort_buffer=(uchar*) my_malloc((sort_param.keys+1) *

				       sort_param.sort_length,

				       MYF(0))))

    return 1;

  sort_param.unique_buff= sort_buffer+(sort_param.keys*

				       sort_param.sort_length);

  sort_param.compare= (qsort2_cmp) buffpek_compare;

  sort_param.cmp_context.key_compare= tree.compare;

  sort_param.cmp_context.key_compare_arg= tree.custom_arg;

  /* Merge the buffers to one file, removing duplicates */

  if (merge_many_buff(&sort_param,sort_buffer,file_ptr,&maxbuffer,&file))

    goto err;

  if (flush_io_cache(&file) ||

      reinit_io_cache(&file,READ_CACHE,0L,0,0))

    goto err;

  if (merge_buffers(&sort_param, &file, outfile, sort_buffer, file_ptr,

		    file_ptr, file_ptr+maxbuffer,0))

    goto err;

  error=0;

err:

  x_free(sort_buffer);

  if (flush_io_cache(outfile))

    error=1;

  /* Setup io_cache for reading */

  save_pos=outfile->pos_in_file;

  if (reinit_io_cache(outfile,READ_CACHE,0L,0,0))

    error=1;

  outfile->end_of_file=save_pos;

  return error;

}