MySQL  8.0.27
Source Code Documentation
cmp_varlen_keys.h
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22 
23 #ifndef CMP_VARLEN_KEYS_INCLUDED
24 #define CMP_VARLEN_KEYS_INCLUDED
25 
26 #include <assert.h>
27 #include <stdio.h>
28 #include <functional>
29 
30 #include "sql/sort_param.h"
31 #include "sql/sql_array.h"
32 
33 /**
34  A compare function for variable-length keys used by filesort().
35  For record format documentation, @see Sort_param.
36 
37  @param sort_field_array array of field descriptors for sorting
38  @param use_hash compare hash values (for grouping of JSON data)
39  @param s1 pointer to record 1
40  @param s2 pointer to record 2
41  @return true/false according to sorting order
42  true : s1 < s2
43  false : s1 >= s2
44  */
45 inline bool cmp_varlen_keys(
46  Bounds_checked_array<st_sort_field> sort_field_array, bool use_hash,
47  const uchar *s1, const uchar *s2) {
50  int res;
51  for (const st_sort_field &sort_field : sort_field_array) {
52  uint kp1_len, kp2_len, kp_len;
53  if (sort_field.maybe_null) {
54  const int k1_nullbyte = *kp1++;
55  const int k2_nullbyte = *kp2++;
56  if (k1_nullbyte != k2_nullbyte) return k1_nullbyte < k2_nullbyte;
57  if (k1_nullbyte == 0 || k1_nullbyte == 0xff) {
58  if (!sort_field.is_varlen) {
59  kp1 += sort_field.length;
60  kp2 += sort_field.length;
61  }
62  continue; // Both key parts are null, nothing to compare
63  }
64  }
65  if (sort_field.is_varlen) {
66  assert(uint4korr(kp1) >= 4);
67  assert(uint4korr(kp2) >= 4);
68 
69  kp1_len = uint4korr(kp1) - 4;
70  kp1 += 4;
71 
72  kp2_len = uint4korr(kp2) - 4;
73  kp2 += 4;
74 
75  kp_len = std::min(kp1_len, kp2_len);
76  } else {
77  kp_len = kp1_len = kp2_len = sort_field.length;
78  }
79 
80  res = memcmp(kp1, kp2, kp_len);
81 
82  if (res) return res < 0;
83  if (kp1_len != kp2_len) {
84  if (sort_field.reverse)
85  return kp2_len < kp1_len;
86  else
87  return kp1_len < kp2_len;
88  }
89 
90  kp1 += kp1_len;
91  kp2 += kp2_len;
92  }
93 
94  if (use_hash) {
95  // Compare hashes at the end of sort keys
96  return memcmp(kp1, kp2, 8) < 0;
97  } else {
98  return false;
99  }
100 }
101 
102 /**
103  This struct is used for merging chunks for filesort()
104  For filesort() with fixed-size keys we use memcmp to compare rows.
105  For variable length keys, we use cmp_varlen_keys to compare rows.
106  */
108  size_t m_len;
110 
111  // CTOR for filesort() with fixed-size keys
112  explicit Merge_chunk_greater(size_t len) : m_len(len), m_param(nullptr) {}
113 
114  // CTOR for filesort() with varlen keys
115  explicit Merge_chunk_greater(Sort_param *param) : m_len(0), m_param(param) {}
116 
117  bool operator()(Merge_chunk *a, Merge_chunk *b) const {
118  return key_is_greater_than(a->current_key(), b->current_key());
119  }
120 
122  // Fixed len keys
123  if (m_len) return memcmp(key1, key2, m_len) > 0;
124 
125  if (m_param)
127  key1);
128 
129  // We can actually have zero-length sort key for filesort().
130  return false;
131  }
132 };
133 
134 #endif // CMP_VARLEN_KEYS_INCLUDED
There are several record formats for sorting:
Definition: sort_param.h:295
Bounds_checked_array< st_sort_field > local_sortorder
ORDER BY list with some precalculated info for filesort.
Definition: sort_param.h:316
static const uint size_of_varlength_field
Definition: sort_param.h:460
bool use_hash
Definition: sort_param.h:304
bool cmp_varlen_keys(Bounds_checked_array< st_sort_field > sort_field_array, bool use_hash, const uchar *s1, const uchar *s2)
A compare function for variable-length keys used by filesort().
Definition: cmp_varlen_keys.h:45
Dialog Client Authentication nullptr
Definition: dialog.cc:352
static uint16 key1[1001]
Definition: hp_test2.cc:46
static uchar key2[100]
Definition: mi_test2.cc:58
uint32 uint4korr(const char *pT)
Definition: my_byteorder.h:144
unsigned char uchar
Definition: my_inttypes.h:51
This struct is used for merging chunks for filesort() For filesort() with fixed-size keys we use memc...
Definition: cmp_varlen_keys.h:107
Merge_chunk_greater(Sort_param *param)
Definition: cmp_varlen_keys.h:115
bool key_is_greater_than(uchar *key1, uchar *key2) const
Definition: cmp_varlen_keys.h:121
Sort_param * m_param
Definition: cmp_varlen_keys.h:109
bool operator()(Merge_chunk *a, Merge_chunk *b) const
Definition: cmp_varlen_keys.h:117
size_t m_len
Definition: cmp_varlen_keys.h:108
Merge_chunk_greater(size_t len)
Definition: cmp_varlen_keys.h:112
Descriptor for a merge chunk to be sort-merged.
Definition: sql_sort.h:56
uchar * current_key() const
Definition: sql_sort.h:85
Struct that holds information about a sort field.
Definition: sort_param.h:85
unsigned int uint
Definition: uca-dump.cc:29