MySQL  8.0.27
Source Code Documentation
merge_many_buff.h
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22 
23 #ifndef MERGE_MANY_BUFF_INCLUDED
24 #define MERGE_MANY_BUFF_INCLUDED
25 
26 #include <algorithm>
27 
28 #include "my_dbug.h"
29 #include "my_sys.h" // open_cached_file
30 #include "sql/mysqld.h" // mysql_tmpdir
31 #include "sql/sql_base.h" // TEMP_PREFIX
32 #include "sql/sql_sort.h" // Sort_buffer
33 
34 class THD;
35 
36 /**
37  Merges buffers to make < MERGEBUFF2 buffers.
38 
39  @param thd thread context
40  @param param Sort parameters.
41  @param sort_buffer The main memory buffer.
42  @param chunk_array Array of chunk descriptors to merge.
43  @param [out] p_num_chunks The number of chunks left in the output file.
44  @param [out] t_file Where to store the result.
45 
46  @returns false if success, true if error
47 */
48 
49 template <typename Merge_param>
50 bool merge_many_buff(THD *thd, Merge_param *param, Sort_buffer sort_buffer,
51  Merge_chunk_array chunk_array, size_t *p_num_chunks,
52  IO_CACHE *t_file) {
53  IO_CACHE t_file2;
54  DBUG_TRACE;
55 
56  size_t num_chunks = chunk_array.size();
57  *p_num_chunks = num_chunks;
58 
59  if (num_chunks <= MERGEBUFF2) return false; /* purecov: inspected */
60 
61  if (flush_io_cache(t_file) ||
63  MYF(MY_WME)))
64  return true; /* purecov: inspected */
65 
66  IO_CACHE *from_file = t_file;
67  IO_CACHE *to_file = &t_file2;
68 
69  while (num_chunks > MERGEBUFF2) {
70  if (reinit_io_cache(from_file, READ_CACHE, 0L, false, false)) goto cleanup;
71  if (reinit_io_cache(to_file, WRITE_CACHE, 0L, false, false)) goto cleanup;
72  Merge_chunk *last_chunk = chunk_array.begin();
73  uint i;
74  for (i = 0; i < num_chunks - MERGEBUFF * 3U / 2U; i += MERGEBUFF) {
75  if (merge_buffers(thd, param, from_file, to_file, sort_buffer,
76  last_chunk++,
77  Merge_chunk_array(&chunk_array[i], MERGEBUFF),
78  /*include_keys=*/true))
79  goto cleanup;
80  }
81  if (merge_buffers(thd, param, from_file, to_file, sort_buffer, last_chunk++,
82  Merge_chunk_array(&chunk_array[i], num_chunks - i),
83  /*include_keys=*/true))
84  break; /* purecov: inspected */
85  if (flush_io_cache(to_file)) break; /* purecov: inspected */
86 
87  std::swap(from_file, to_file);
88  setup_io_cache(from_file);
89  setup_io_cache(to_file);
90  num_chunks = last_chunk - chunk_array.begin();
91  }
92 cleanup:
93  close_cached_file(to_file); // This holds old result
94  if (to_file == t_file) {
95  *t_file = t_file2; // Copy result file
96  setup_io_cache(t_file);
97  }
98 
99  *p_num_chunks = num_chunks;
100  return num_chunks > MERGEBUFF2; /* Return true if interrupted */
101 } /* merge_many_buff */
102 
103 #endif // MERGE_MANY_BUFF_INCLUDED
A wrapper class which provides array bounds checking.
Definition: sql_array.h:46
iterator begin()
begin : Returns a pointer to the first element in the array.
Definition: sql_array.h:116
size_t size() const
Definition: sql_array.h:131
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:821
void cleanup(void)
Definition: sql_class.cc:974
#define L
Definition: ctype-tis620.cc:75
DBUG_TRACE
Definition: do_ctype.cc:46
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:1832
void close_cached_file(IO_CACHE *cache)
Definition: mf_cache.cc:86
#define MY_WME
Definition: my_sys.h:122
void setup_io_cache(IO_CACHE *info)
Definition: mf_iocache.cc:117
#define flush_io_cache(info)
Definition: my_sys.h:757
bool reinit_io_cache(IO_CACHE *info, enum cache_type type, my_off_t seek_offset, bool use_async_io, bool clear_cache)
bool open_cached_file(IO_CACHE *cache, const char *dir, const char *prefix, size_t cache_size, myf cache_myflags)
Definition: mf_cache.cc:52
@ WRITE_CACHE
Definition: my_sys.h:284
@ READ_CACHE
Definition: my_sys.h:283
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:50
#define MYF(v)
Definition: my_inttypes.h:96
Common header for many mysys elements.
#define mysql_tmpdir
Definition: mysqld.h:680
#define TEMP_PREFIX
Definition: sql_base.h:77
#define DISK_BUFFER_SIZE
Definition: sql_const.h:142
constexpr size_t MERGEBUFF2
Definition: sql_sort.h:40
Bounds_checked_array< Merge_chunk > Merge_chunk_array
Definition: sql_sort.h:131
constexpr size_t MERGEBUFF
Definition: sql_sort.h:39
static void swap(String &a, String &b) noexcept
Definition: sql_string.h:610
Definition: my_sys.h:340
Descriptor for a merge chunk to be sort-merged.
Definition: sql_sort.h:56
unsigned int uint
Definition: uca-dump.cc:29