MySQL 8.4.3
Source Code Documentation
merge_many_buff.h
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23
24#ifndef MERGE_MANY_BUFF_INCLUDED
25#define MERGE_MANY_BUFF_INCLUDED
26
27#include <algorithm>
28
29#include "my_dbug.h"
30#include "my_sys.h" // open_cached_file
31#include "sql/mysqld.h" // mysql_tmpdir
32#include "sql/sql_base.h" // TEMP_PREFIX
33#include "sql/sql_sort.h" // Sort_buffer
34
35class THD;
36
37/**
38 Merges buffers to make < MERGEBUFF2 buffers.
39
40 @param thd thread context
41 @param param Sort parameters.
42 @param sort_buffer The main memory buffer.
43 @param chunk_array Array of chunk descriptors to merge.
44 @param [out] p_num_chunks The number of chunks left in the output file.
45 @param [out] t_file Where to store the result.
46
47 @returns false if success, true if error
48*/
49
50template <typename Merge_param>
51bool merge_many_buff(THD *thd, Merge_param *param, Sort_buffer sort_buffer,
52 Merge_chunk_array chunk_array, size_t *p_num_chunks,
53 IO_CACHE *t_file) {
54 IO_CACHE t_file2;
56
57 size_t num_chunks = chunk_array.size();
58 *p_num_chunks = num_chunks;
59
60 if (num_chunks <= MERGEBUFF2) return false; /* purecov: inspected */
61
62 if (flush_io_cache(t_file) ||
64 MYF(MY_WME)))
65 return true; /* purecov: inspected */
66
67 IO_CACHE *from_file = t_file;
68 IO_CACHE *to_file = &t_file2;
69
70 while (num_chunks > MERGEBUFF2) {
71 if (reinit_io_cache(from_file, READ_CACHE, 0L, false, false)) goto cleanup;
72 if (reinit_io_cache(to_file, WRITE_CACHE, 0L, false, false)) goto cleanup;
73 Merge_chunk *last_chunk = chunk_array.begin();
74 uint i;
75 for (i = 0; i < num_chunks - MERGEBUFF * 3U / 2U; i += MERGEBUFF) {
76 if (merge_buffers(thd, param, from_file, to_file, sort_buffer,
77 last_chunk++,
78 Merge_chunk_array(&chunk_array[i], MERGEBUFF),
79 /*include_keys=*/true))
80 goto cleanup;
81 }
82 if (merge_buffers(thd, param, from_file, to_file, sort_buffer, last_chunk++,
83 Merge_chunk_array(&chunk_array[i], num_chunks - i),
84 /*include_keys=*/true))
85 break; /* purecov: inspected */
86 if (flush_io_cache(to_file)) break; /* purecov: inspected */
87
88 std::swap(from_file, to_file);
89 setup_io_cache(from_file);
90 setup_io_cache(to_file);
91 num_chunks = last_chunk - chunk_array.begin();
92 }
94 close_cached_file(to_file); // This holds old result
95 if (to_file == t_file) {
96 *t_file = t_file2; // Copy result file
97 setup_io_cache(t_file);
98 }
99
100 *p_num_chunks = num_chunks;
101 return num_chunks > MERGEBUFF2; /* Return true if interrupted */
102} /* merge_many_buff */
103
104#endif // MERGE_MANY_BUFF_INCLUDED
A wrapper class which provides array bounds checking.
Definition: sql_array.h:47
iterator begin()
begin : Returns a pointer to the first element in the array.
Definition: sql_array.h:134
size_t size() const
Definition: sql_array.h:154
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_lexer_thd.h:36
void cleanup(void)
Definition: sql_class.cc:1238
#define L
Definition: ctype-tis620.cc:75
static int merge_buffers(THD *thd, Sort_param *param, IO_CACHE *from_file, IO_CACHE *to_file, Sort_buffer sort_buffer, Merge_chunk *last_chunk, Merge_chunk_array chunk_array, bool include_keys)
Merge buffers to one buffer.
Definition: filesort.cc:1911
void close_cached_file(IO_CACHE *cache)
Definition: mf_cache.cc:87
#define MY_WME
Definition: my_sys.h:128
void setup_io_cache(IO_CACHE *info)
Definition: mf_iocache.cc:117
#define flush_io_cache(info)
Definition: my_sys.h:766
bool reinit_io_cache(IO_CACHE *info, enum cache_type type, my_off_t seek_offset, bool use_async_io, bool clear_cache)
Definition: mf_iocache.cc:328
bool open_cached_file(IO_CACHE *cache, const char *dir, const char *prefix, size_t cache_size, myf cache_myflags)
Definition: mf_cache.cc:53
@ WRITE_CACHE
Definition: my_sys.h:290
@ READ_CACHE
Definition: my_sys.h:289
bool merge_many_buff(THD *thd, Merge_param *param, Sort_buffer sort_buffer, Merge_chunk_array chunk_array, size_t *p_num_chunks, IO_CACHE *t_file)
Merges buffers to make < MERGEBUFF2 buffers.
Definition: merge_many_buff.h:51
#define DBUG_TRACE
Definition: my_dbug.h:146
#define MYF(v)
Definition: my_inttypes.h:97
constexpr const unsigned int DISK_BUFFER_SIZE
Definition: my_io.h:164
Common header for many mysys elements.
#define mysql_tmpdir
Definition: mysqld.h:683
#define TEMP_PREFIX
Definition: sql_base.h:79
constexpr size_t MERGEBUFF2
Definition: sql_sort.h:41
Bounds_checked_array< Merge_chunk > Merge_chunk_array
Definition: sql_sort.h:143
constexpr size_t MERGEBUFF
Definition: sql_sort.h:40
static void swap(String &a, String &b) noexcept
Definition: sql_string.h:663
Definition: my_sys.h:346
Descriptor for a merge chunk to be sort-merged.
Definition: sql_sort.h:57