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mariadb/sql/uniques.cc
Monty eb483c5181 Updated optimizer costs in multi_range_read_info_const() and sql_select.cc 
- multi_range_read_info_const now uses the new records_in_range interface
- Added handler::avg_io_cost()
- Don't calculate avg_io_cost() in get_sweep_read_cost if avg_io_cost is
  not 1.0.  In this case we trust the avg_io_cost() from the handler.
- Changed test_quick_select to use TIME_FOR_COMPARE instead of
  TIME_FOR_COMPARE_IDX to align this with the rest of the code.
- Fixed bug when using test_if_cheaper_ordering where we didn't use
  keyread if index was changed
- Fixed a bug where we didn't use index only read when using order-by-index
- Added keyread_time() to HEAP.
  The default keyread_time() was optimized for blocks and not suitable for
  HEAP. The effect was the HEAP prefered table scans over ranges for btree
  indexes.
- Fixed get_sweep_read_cost() for HEAP tables
- Ensure that range and ref have same cost for simple ranges
  Added a small cost (MULTI_RANGE_READ_SETUP_COST) to ranges to ensure
  we favior ref for range for simple queries.
- Fixed that matching_candidates_in_table() uses same number of records
  as the rest of the optimizer
- Added avg_io_cost() to JT_EQ_REF cost. This helps calculate the cost for
  HEAP and temporary tables better. A few tests changed because of this.
- heap::read_time() and heap::keyread_time() adjusted to not add +1.
  This was to ensure that handler::keyread_time() doesn't give
  higher cost for heap tables than for normal tables. One effect of
  this is that heap and derived tables stored in heap will prefer
  key access as this is now regarded as cheap.
- Changed cost for index read in sql_select.cc to match
  multi_range_read_info_const(). All index cost calculation is now
  done trough one function.
- 'ref' will now use quick_cost for keys if it exists. This is done
  so that for '=' ranges, 'ref' is prefered over 'range'.
- scan_time() now takes avg_io_costs() into account
- get_delayed_table_estimates() uses block_size and avg_io_cost()
- Removed default argument to test_if_order_by_key(); simplifies code
2020-03-27 03:58:32 +02:00

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/* Copyright (c) 2001, 2010, Oracle and/or its affiliates.
Copyright (c) 2010, 2015, MariaDB
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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 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 "mariadb.h"
#include "sql_priv.h"
#include "unireg.h"
#include "sql_sort.h"
#include "queues.h" // QUEUE
#include "my_tree.h" // element_count
#include "uniques.h" // Unique
#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_file_with_count(uchar* key, element_count count, Unique *unique)
{
return my_b_write(&unique->file, key, unique->size) ||
my_b_write(&unique->file, (uchar*)&count, sizeof(element_count)) ? 1 : 0;
}
int unique_write_to_ptrs(uchar* key, element_count count, Unique *unique)
{
memcpy(unique->sort.record_pointers, key, unique->size);
unique->sort.record_pointers+=unique->size;
return 0;
}
int unique_intersect_write_to_ptrs(uchar* key, element_count count, Unique *unique)
{
if (count >= unique->min_dupl_count)
{
memcpy(unique->sort.record_pointers, key, unique->size);
unique->sort.record_pointers+=unique->size;
}
else
unique->filtered_out_elems++;
return 0;
}
Unique::Unique(qsort_cmp2 comp_func, void * comp_func_fixed_arg,
uint size_arg, size_t max_in_memory_size_arg,
uint min_dupl_count_arg)
:max_in_memory_size(max_in_memory_size_arg),
size(size_arg),
elements(0)
{
my_b_clear(&file);
min_dupl_count= min_dupl_count_arg;
full_size= size;
if (min_dupl_count_arg)
full_size+= sizeof(element_count);
with_counters= MY_TEST(min_dupl_count_arg);
init_tree(&tree, (max_in_memory_size / 16), 0, size, comp_func,
NULL, comp_func_fixed_arg, MYF(MY_THREAD_SPECIFIC));
/* If the following fail's the next add will also fail */
my_init_dynamic_array(PSI_INSTRUMENT_ME, &file_ptrs, sizeof(Merge_chunk), 16,
16, MYF(MY_THREAD_SPECIFIC));
/*
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));
if (!max_elements)
max_elements= 1;
(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,
double compare_factor)
{
uint total_buf_elems= 0;
for (uint *pbuf= first; pbuf <= last; pbuf++)
total_buf_elems+= *pbuf;
*last= total_buf_elems;
size_t 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) / (compare_factor * 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,
double compare_factor)
{
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,
compare_factor);
lastbuff++;
}
total_cost+=get_merge_buffers_cost(buff_elems, elem_size,
buff_elems + i,
buff_elems + maxbuffer,
compare_factor);
maxbuffer= lastbuff;
}
}
/* Simulate final merge_buff call. */
total_cost += get_merge_buffers_cost(buff_elems, elem_size,
buff_elems, buff_elems + maxbuffer,
compare_factor);
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
compare_factor used to calculate cost of one comparison
write_fl if the result must be saved written to disk
in_memory_elems OUT estimate of the number of elements in memory
if disk is not used
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, size_t nkeys, uint key_size,
size_t max_in_memory_size,
double compare_factor,
bool intersect_fl, bool *in_memory)
{
size_t max_elements_in_tree;
size_t last_tree_elems;
size_t n_full_trees; /* number of trees in unique - 1 */
double result;
max_elements_in_tree= ((size_t) 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 /= compare_factor;
DBUG_PRINT("info",("unique trees sizes: %u=%u*%u + %u", (uint)nkeys,
(uint)n_full_trees,
(uint)(n_full_trees?max_elements_in_tree:0),
(uint)last_tree_elems));
if (in_memory)
*in_memory= !n_full_trees;
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 */
if (intersect_fl)
key_size+= sizeof(element_count);
double merge_cost= get_merge_many_buffs_cost(buffer, (uint)n_full_trees,
(uint)max_elements_in_tree,
(uint)last_tree_elems, key_size,
compare_factor);
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, 0);
delete_dynamic(&file_ptrs);
}
/* Write tree to disk; clear tree */
bool Unique::flush()
{
Merge_chunk file_ptr;
elements+= tree.elements_in_tree;
file_ptr.set_rowcount(tree.elements_in_tree);
file_ptr.set_file_position(my_b_tell(&file));
tree_walk_action action= min_dupl_count ?
(tree_walk_action) unique_write_to_file_with_count :
(tree_walk_action) unique_write_to_file;
if (tree_walk(&tree, action,
(void*) this, left_root_right) ||
insert_dynamic(&file_ptrs, (uchar*) &file_ptr))
return 1;
delete_tree(&tree, 0);
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);
}
my_free(sort.record_pointers);
elements= 0;
tree.flag= 0;
sort.record_pointers= 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
inline
element_count get_counter_from_merged_element(void *ptr, uint ofs)
{
element_count cnt;
memcpy((uchar *) &cnt, (uchar *) ptr + ofs, sizeof(element_count));
return cnt;
}
inline
void put_counter_into_merged_element(void *ptr, uint ofs, element_count cnt)
{
memcpy((uchar *) ptr + ofs, (uchar *) &cnt, sizeof(element_count));
}
/*
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.
with counters take into account counters for equal merged
elements
RETURN VALUE
0 ok
<> 0 error
*/
static bool merge_walk(uchar *merge_buffer, size_t merge_buffer_size,
uint key_length, Merge_chunk *begin, Merge_chunk *end,
tree_walk_action walk_action, void *walk_action_arg,
qsort_cmp2 compare, void *compare_arg,
IO_CACHE *file, bool with_counters)
{
BUFFPEK_COMPARE_CONTEXT compare_context = { compare, compare_arg };
QUEUE queue;
if (end <= begin ||
merge_buffer_size < (size_t) (key_length * (end - begin + 1)) ||
init_queue(&queue, (uint) (end - begin),
offsetof(Merge_chunk, m_current_key), 0,
buffpek_compare, &compare_context, 0, 0))
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;
ulong bytes_read; /* to hold return value of read_to_buffer */
Merge_chunk *top;
int res= 1;
uint cnt_ofs= key_length - (with_counters ? sizeof(element_count) : 0);
element_count cnt;
// read_to_buffer() needs only rec_length.
Sort_param sort_param;
sort_param.rec_length= key_length;
DBUG_ASSERT(!sort_param.using_addon_fields());
/*
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->set_buffer(merge_buffer + (top - begin) * piece_size,
merge_buffer + (top - begin) * piece_size + piece_size);
top->set_max_keys(max_key_count_per_piece);
bytes_read= read_to_buffer(file, top, &sort_param, false);
if (unlikely(bytes_read == (ulong) -1))
goto end;
DBUG_ASSERT(bytes_read);
queue_insert(&queue, (uchar *) top);
}
top= (Merge_chunk *) 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->current_key();
/*
read next key from the cache or from the file and push it to the
queue; this gives new top.
*/
top->advance_current_key(key_length);
top->decrement_mem_count();
if (top->mem_count())
queue_replace_top(&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, &sort_param, false);
if (unlikely(bytes_read == (ulong) -1))
goto end;
else if (bytes_read) /* top->key, top->mem_count are reset */
queue_replace_top(&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_top(&queue);
reuse_freed_buff(&queue, top, key_length);
}
}
top= (Merge_chunk *) queue_top(&queue);
/* new top has been obtained; if old top is unique, apply the action */
if (compare(compare_arg, old_key, top->current_key()))
{
cnt= with_counters ?
get_counter_from_merged_element(old_key, cnt_ofs) : 1;
if (walk_action(old_key, cnt, walk_action_arg))
goto end;
}
else if (with_counters)
{
cnt= get_counter_from_merged_element(top->current_key(), cnt_ofs);
cnt+= get_counter_from_merged_element(old_key, cnt_ofs);
put_counter_into_merged_element(top->current_key(), cnt_ofs, cnt);
}
}
/*
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
{
cnt= with_counters ?
get_counter_from_merged_element(top->current_key(), cnt_ofs) : 1;
if (walk_action(top->current_key(), cnt, walk_action_arg))
goto end;
top->advance_current_key(key_length);
}
while (top->decrement_mem_count());
bytes_read= read_to_buffer(file, top, &sort_param, false);
if (unlikely(bytes_read == (ulong) -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':
table parameter for the call of the merge method
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(TABLE *table, tree_walk_action action, void *walk_action_arg)
{
int res= 0;
uchar *merge_buffer;
if (elements == 0) /* the whole tree is in memory */
return tree_walk(&tree, action, walk_action_arg, left_root_right);
sort.return_rows= elements+tree.elements_in_tree;
/* 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;
/*
merge_buffer must fit at least MERGEBUFF2 + 1 keys, because
merge_index() can merge that many BUFFPEKs at once. The extra space for one key
is needed when a piece of merge buffer is re-read, see merge_walk()
*/
size_t buff_sz= MY_MAX(MERGEBUFF2+1, max_in_memory_size/full_size+1) * full_size;
if (!(merge_buffer = (uchar *)my_malloc(key_memory_Unique_merge_buffer,
buff_sz, MYF(MY_THREAD_SPECIFIC|MY_WME))))
return 1;
if (buff_sz < full_size * (file_ptrs.elements + 1UL))
res= merge(table, merge_buffer, buff_sz,
buff_sz >= full_size * MERGEBUFF2) ;
if (!res)
{
res= merge_walk(merge_buffer, buff_sz, full_size,
(Merge_chunk *) file_ptrs.buffer,
(Merge_chunk *) file_ptrs.buffer + file_ptrs.elements,
action, walk_action_arg,
tree.compare, tree.custom_arg, &file, with_counters);
}
my_free(merge_buffer);
return res;
}
/*
DESCRIPTION
Perform multi-pass sort merge of the elements using the buffer buff as
the merge buffer. The last pass is not performed if without_last_merge is
TRUE.
SYNOPSIS
Unique:merge()
All params are 'IN':
table the parameter to access sort context
buff merge buffer
buff_size size of merge buffer
without_last_merge TRUE <=> do not perform the last merge
RETURN VALUE
0 OK
<> 0 error
*/
bool Unique::merge(TABLE *table, uchar *buff, size_t buff_size,
bool without_last_merge)
{
IO_CACHE *outfile= &sort.io_cache;
Merge_chunk *file_ptr= (Merge_chunk*) file_ptrs.buffer;
uint maxbuffer= file_ptrs.elements - 1;
my_off_t save_pos;
bool error= 1;
Sort_param sort_param;
/* Open cached file for table records if it isn't open */
if (! my_b_inited(outfile) &&
open_cached_file(outfile,mysql_tmpdir,TEMP_PREFIX,READ_RECORD_BUFFER,
MYF(MY_WME)))
return 1;
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=
full_size;
sort_param.min_dupl_count= min_dupl_count;
sort_param.res_length= 0;
sort_param.max_keys_per_buffer=
(uint) MY_MAX((max_in_memory_size / sort_param.sort_length), MERGEBUFF2);
sort_param.not_killable= 1;
sort_param.unique_buff= buff +(sort_param.max_keys_per_buffer *
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,
Bounds_checked_array<uchar>(buff, buff_size),
file_ptr,&maxbuffer,&file))
goto err;
if (flush_io_cache(&file) ||
reinit_io_cache(&file,READ_CACHE,0L,0,0))
goto err;
sort_param.res_length= sort_param.rec_length-
(min_dupl_count ? sizeof(min_dupl_count) : 0);
if (without_last_merge)
{
file_ptrs.elements= maxbuffer+1;
return 0;
}
if (merge_index(&sort_param, Bounds_checked_array<uchar>(buff, buff_size),
file_ptr, maxbuffer, &file, outfile))
goto err;
error= 0;
err:
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;
}
/*
Allocate memory that can be used with init_records() so that
rows will be read in priority order.
*/
bool Unique::get(TABLE *table)
{
bool rc= 1;
uchar *sort_buffer= NULL;
sort.return_rows= elements+tree.elements_in_tree;
DBUG_ENTER("Unique::get");
if (my_b_tell(&file) == 0)
{
/* Whole tree is in memory; Don't use disk if you don't need to */
if ((sort.record_pointers= (uchar*)
my_malloc(key_memory_Filesort_info_record_pointers,
size * tree.elements_in_tree, MYF(MY_THREAD_SPECIFIC))))
{
uchar *save_record_pointers= sort.record_pointers;
tree_walk_action action= min_dupl_count ?
(tree_walk_action) unique_intersect_write_to_ptrs :
(tree_walk_action) unique_write_to_ptrs;
filtered_out_elems= 0;
(void) tree_walk(&tree, action,
this, left_root_right);
/* Restore record_pointers that was changed in by 'action' above */
sort.record_pointers= save_record_pointers;
sort.return_rows-= filtered_out_elems;
DBUG_RETURN(0);
}
}
/* Not enough memory; Save the result to file && free memory used by tree */
if (flush())
DBUG_RETURN(1);
size_t buff_sz= (max_in_memory_size / full_size + 1) * full_size;
if (!(sort_buffer= (uchar*) my_malloc(key_memory_Unique_sort_buffer, buff_sz,
MYF(MY_THREAD_SPECIFIC|MY_WME))))
DBUG_RETURN(1);
if (merge(table, sort_buffer, buff_sz, FALSE))
goto err;
rc= 0;
err:
my_free(sort_buffer);
DBUG_RETURN(rc);
}
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