-
Notifications
You must be signed in to change notification settings - Fork 0
/
main.c
1038 lines (919 loc) · 31.9 KB
/
main.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
#include "main.h"
const uint32_t ID_SIZE = size_of_attribute(Row, id);
const uint32_t USERNAME_SIZE = size_of_attribute(Row, username);
const uint32_t EMAIL_SIZE = size_of_attribute(Row, email);
const uint32_t ID_OFFSET = 0;
const uint32_t USERNAME_OFFSET = ID_OFFSET + ID_SIZE;
const uint32_t EMAIL_OFFSET = USERNAME_OFFSET + USERNAME_SIZE;
const uint32_t ROW_SIZE = ID_SIZE + USERNAME_SIZE + EMAIL_SIZE;
const uint32_t ROWS_PER_PAGE = PAGE_SIZE / ROW_SIZE;
const uint32_t TABLE_MAX_ROWS = ROWS_PER_PAGE * TABLE_MAX_PAGES;
// 公共节点头部布局
// 1. 节点类型
// 2. 是否是根节点
// 3. 父节点指针
const uint32_t NODE_TYPE_SIZE = sizeof(uint8_t); // 1 Byte
const uint32_t NODE_TYPE_OFFSET = 0;
const uint32_t IS_ROOT_SIZE = sizeof(uint8_t); // 1 Byte
const uint32_t IS_ROOT_OFFSET = NODE_TYPE_SIZE;
const uint32_t PARENT_POINTER_SIZE = sizeof(uint32_t); // 4 Byte
const uint32_t PARENT_POINTER_OFFSET = IS_ROOT_OFFSET + IS_ROOT_SIZE;
const uint32_t COMMON_NODE_HEADER_SIZE = NODE_TYPE_SIZE + IS_ROOT_SIZE + PARENT_POINTER_SIZE; // 6 Byte
// 叶子节点头部布局
// 1. 单元的数量
// 2. 下一个节点
const uint32_t LEAF_NODE_NUM_CELLS_SIZE = sizeof(uint32_t); // 4 Byte
const uint32_t LEAF_NODE_NUM_CELLS_OFFSET = COMMON_NODE_HEADER_SIZE;
const uint32_t LEAF_NODE_NEXT_LEAF_SIZE = sizeof(uint32_t);
const uint32_t LEAF_NODE_NEXT_LEAF_OFFSET = LEAF_NODE_NUM_CELLS_OFFSET + LEAF_NODE_NUM_CELLS_SIZE;
const uint32_t LEAF_NODE_HEADER_SIZE = COMMON_NODE_HEADER_SIZE + LEAF_NODE_NUM_CELLS_SIZE + LEAF_NODE_NEXT_LEAF_SIZE; // 14 Byte
// 叶子节点体布局
// 1. 键
// 2. 数据
const uint32_t LEAF_NODE_KEY_SIZE = sizeof(uint32_t); // 4 Byte
const uint32_t LEAF_NODE_KEY_OFFSET = 0;
const uint32_t LEAF_NODE_VALUE_SIZE = ROW_SIZE;
const uint32_t LEAF_NODE_VALUE_OFFSET = LEAF_NODE_KEY_SIZE;
const uint32_t LEAF_NODE_CELL_SIZE = LEAF_NODE_KEY_SIZE + LEAF_NODE_VALUE_SIZE;
const uint32_t LEAF_NODE_SPACE_FOR_CELLS = PAGE_SIZE - LEAF_NODE_HEADER_SIZE;
const uint32_t LEAF_NODE_MAX_CELLS = LEAF_NODE_SPACE_FOR_CELLS / LEAF_NODE_CELL_SIZE;
// 需把插入数据算入,左边的数>=右边的数
const uint32_t LEAF_NODE_RIGHT_SPLIT_COUNT = (LEAF_NODE_MAX_CELLS + 1) / 2;
const uint32_t LEAF_NODE_LEFT_SPLIT_COUNT = (LEAF_NODE_MAX_CELLS + 1) - LEAF_NODE_RIGHT_SPLIT_COUNT;
// 内部节点头部布局
const uint32_t INTERNAL_NODE_NUM_KEYS_SIZE = sizeof(uint32_t); // 子节点的数比键数多1
const uint32_t INTERNAL_NODE_NUM_KEYS_OFFSET = COMMON_NODE_HEADER_SIZE;
const uint32_t INTERNAL_NODE_RIGHT_CHILD_SIZE = sizeof(uint32_t); // 存放最右边的子节点
const uint32_t INTERNAL_NODE_RIGHT_CHILD_OFFSET = INTERNAL_NODE_NUM_KEYS_OFFSET + INTERNAL_NODE_NUM_KEYS_SIZE;
const uint32_t INTERNAL_NODE_HEADER_SIZE = COMMON_NODE_HEADER_SIZE + INTERNAL_NODE_NUM_KEYS_SIZE + INTERNAL_NODE_RIGHT_CHILD_SIZE;
// 内部节点体布局
const uint32_t INTERNAL_NODE_CHILD_SIZE = sizeof(uint32_t);
const uint32_t INTERNAL_NODE_KEY_SIZE = sizeof(uint32_t);
const uint32_t INTERNAL_NODE_CELL_SIZE = INTERNAL_NODE_CHILD_SIZE + INTERNAL_NODE_KEY_SIZE;
InputBuffer* new_input_buffer(void);
void print_prompt(void);
void read_input(InputBuffer* input_buffer);
void close_input_buffer(InputBuffer* input_buffer);
Table* db_open(const char* filename);
void db_close(Table* table);
MetaCommandResult do_meta_command(InputBuffer *input_buffer, Table* table);
PrepareResult prepare_insert(InputBuffer *input_buffer, Statement *statement);
PrepareResult prepare_statement(InputBuffer *input_buffer, Statement *statement);
void serialize_row(Row* source, void* destination);
void deserialize_row(void* source, Row* destination);
void* get_page(Pager* pager, uint32_t page_num);
void* row_slot(Table* table, uint32_t row_num);
ExecuteResult execute_insert(Statement* statement, Table* table);
void print_row(Row* row);
ExecuteResult execute_select(Statement* statement, Table* table);
Pager* pager_open(const char* filename);
void pager_flush(Pager* pager, uint32_t i);
void free_table(Table* table);
ExecuteResult execute_statement(Statement* statement, Table* table);
Cursor* table_start(Table* table);
Cursor* table_end(Table* table);
void cursor_advance(Cursor* cursor);
void print_constants(void);
void print_leaf_node(void* node);
uint32_t* leaf_node_num_cells(void* node);
void* leaf_node_cell(void* node, uint32_t cell_num);
uint32_t* leaf_node_key(void* node, uint32_t cell_num);
void* leaf_node_value(void* node, uint32_t cell_num);
void initialize_leaf_node(void* node);
NodeType get_node_type(void* node);
void set_node_type(void* node, NodeType type);
void leaf_node_insert(Cursor* cursor, uint32_t key, Row* value);
Cursor* table_find(Table* table, uint32_t key);
Cursor* leaf_node_find(Table* table,uint32_t page_num, uint32_t key);
void leaf_node_split_and_insert(Cursor* cursor,uint32_t key,Row* value);
uint32_t get_unused_page_num(Pager* pager);
bool is_node_root(void* node);
void set_node_root(void* node, bool is_root);
void create_new_root(Table* table, uint32_t page_num);
uint32_t* internal_node_child(void* node, uint32_t child_num);
uint32_t* internal_node_key(void* node, uint32_t key_num);
uint32_t get_node_max_key(void* node);
uint32_t* internal_node_right_child(void* node);
uint32_t* internal_node_num_keys(void* node);
void indent(uint32_t level);
void print_tree(Pager* pager, uint32_t page_num, uint32_t indentation_level);
Cursor* internal_node_find(Table* table, uint32_t root_page_num, uint32_t key);
uint32_t* leaf_node_next_leaf(void* node);
// 创建输入缓存
InputBuffer* new_input_buffer()
{
InputBuffer* input_buffer = malloc(sizeof(InputBuffer));
input_buffer->buffer = NULL;
input_buffer->buffer_length = 0;
input_buffer->input_length = 0;
return input_buffer;
}
// 命令前显示
void print_prompt()
{
printf("db > ");
}
// 读取一行输入到输入缓存
void read_input(InputBuffer* input_buffer)
{
// lineptr:指向存放该行字符的指针,如果是NULL,则有系统帮助malloc,请在使用完成后free释放。
// n:如果是由系统malloc的指针,请填0
ssize_t bytes_read = getline(&(input_buffer->buffer), &(input_buffer->buffer_length), stdin);
if(bytes_read <= 0) {
printf("Error reading input\n");
exit(EXIT_FAILURE);
}
// 删除换行符
input_buffer->input_length = bytes_read - 1;
input_buffer->buffer[bytes_read - 1] = 0;
}
// 释放输入缓存
void close_input_buffer(InputBuffer* input_buffer)
{
free(input_buffer->buffer);
free(input_buffer);
}
// 关闭数据库
void db_close(Table* table)
{
Pager* pager = table->pager;
// 1. 将完整页存入磁盘,并释放内存
for(uint32_t i = 0; i < pager->num_pages; i++) {
if (pager->pages[i] == NULL) {
continue;
}
pager_flush(pager, i); // 将整页存入磁盘
free(pager->pages[i]); // 释放内存
pager->pages[i] = NULL;
}
// 2. 关闭文件
int result = close(pager->file_descriptor);
if (result == -1) {
printf("Error closing db file.\n");
exit(EXIT_FAILURE);
}
// 3. 释放内存
for (uint32_t i = 0; i < TABLE_MAX_PAGES; i++) {
void* page = pager->pages[i];
if (page) {
free(page);
pager->pages[i] = NULL;
}
}
free(pager);
free(table);
}
// 执行元命令
MetaCommandResult do_meta_command(InputBuffer *input_buffer, Table* table)
{
// 退出
if (strcmp(input_buffer->buffer, ".exit") == 0) {
// 1. 关闭数据库
db_close(table);
// 2. 释放输入缓存
close_input_buffer(input_buffer);
exit(EXIT_SUCCESS);
}
else if (strcmp(input_buffer->buffer, ".constants") == 0) {
printf("Constants:\n");
print_constants();
return META_COMMAND_SUCCESS;
}
else if (strcmp(input_buffer->buffer, ".btree") == 0) {
printf("Tree:\n");
// print_leaf_node(get_page(table->pager, 0));
print_tree(table->pager, 0, 0);
return META_COMMAND_SUCCESS;
}
else {
return META_COMMAND_UNRECOGNIZED_COMMAND;
}
}
// 准备插入
// 从输入缓存中解析出插入数据
PrepareResult prepare_insert(InputBuffer *input_buffer, Statement *statement)
{
// 1. 设置类型
statement->type = STATEMENT_INSERT;
// 2. 分离输入
char* keyword = strtok(input_buffer->buffer, " ");
char* id_string = strtok(NULL, " ");
char* username = strtok(NULL, " ");
char* email = strtok(NULL, " ");
// 3. 校验输入
if (id_string == NULL || username == NULL || email == NULL) {
return PREPARE_SYNTAX_ERROR;
}
int id = atoi(id_string);
if (id < 0) {
return PREPARE_NEGATIVE_ID;
}
if (strlen(username) > COLUMN_USERNAME_SIZE) {
return PREPARE_STRING_TOO_LONG;
}
if (strlen(email) > COLUMN_EMAIL_SIZE) {
return PREPARE_STRING_TOO_LONG;
}
// 4. 设置数据
statement->row_to_insert.id = id;
strcpy(statement->row_to_insert.username, username);
strcpy(statement->row_to_insert.email, email);
return PREPARE_SUCCESS;
}
// 准备语句
// 根据输入首个词,确认不同操作,并分别进行解析
PrepareResult prepare_statement(InputBuffer *input_buffer, Statement *statement)
{
if (strncmp(input_buffer->buffer, "insert", 6) == 0) {
return prepare_insert(input_buffer, statement);
}
if (strcmp(input_buffer->buffer, "select") == 0) {
statement->type = STATEMENT_SELECT;
return PREPARE_SUCCESS;
}
return PREPARE_UNRECOGNIZED_STATEMENT;
}
// 序列化行
void serialize_row(Row* source, void* destination)
{
memcpy(destination + ID_OFFSET, &(source->id), ID_SIZE);
strncpy(destination + USERNAME_OFFSET, source->username, USERNAME_SIZE);
strncpy(destination + EMAIL_OFFSET, source->email, EMAIL_SIZE);
}
// 反序列化行
void deserialize_row(void* source, Row* destination)
{
memcpy(&(destination->id), source+ID_OFFSET, ID_SIZE);
memcpy(&(destination->username), source+USERNAME_OFFSET, USERNAME_SIZE);
memcpy(&(destination->email), source+EMAIL_OFFSET, EMAIL_SIZE);
}
// 根据页数获取页地址,如果为空,从磁盘中读
// pager: 分页器
// page_num: 第几页
void* get_page(Pager* pager, uint32_t page_num)
{
// 1. 页数是否超限
if(page_num > TABLE_MAX_PAGES) {
printf("Tried to fetch page number out of bounds. %d > %d\n", page_num, TABLE_MAX_PAGES);
exit(EXIT_FAILURE);
}
// 2. 如果内存中页内容为空,从磁盘中读取
if(pager->pages[page_num] == NULL) {
// 创建页内存
void* page = malloc(PAGE_SIZE);
// 计算磁盘文件中页数
uint32_t num_pages = pager->file_length / PAGE_SIZE;
if (pager->file_length % PAGE_SIZE) {
num_pages += 1;
}
// 从磁盘中读取数据
if (page_num <= num_pages) {
// 移动到第几页
lseek(pager->file_descriptor, page_num * PAGE_SIZE, SEEK_SET);
// 读取整页
ssize_t bytes_read = read(pager->file_descriptor, page, PAGE_SIZE);
if (bytes_read == -1) {
printf("Error reading file: %d\n", errno);
exit(EXIT_FAILURE);
}
}
pager->pages[page_num] = page;
// 如果获取的页数大于等于记录的页数,增加页
if (page_num >= pager->num_pages) {
pager->num_pages = page_num + 1;
}
}
return pager->pages[page_num];
}
// 根据行数返回数据地址
void* cursor_value(Cursor* cursor)
{
printf("cursor_value page_num:%d cell_num:%d\n", cursor->page_num, cursor->cell_num);
uint32_t page_num = cursor->page_num;
void* page = get_page(cursor->table->pager, page_num);
return leaf_node_value(page, cursor->cell_num);
}
// 将行插入到表中
ExecuteResult execute_insert(Statement* statement, Table* table)
{
void* node = get_page(table->pager, table->root_page_num);
uint32_t num_cells = (*leaf_node_num_cells(node));
// 根据键值找到游标
Row* row_to_insert = &(statement->row_to_insert);
uint32_t key_to_insert = row_to_insert->id;
Cursor* cursor = table_find(table, key_to_insert);
// id 重复,返回错误
if (cursor->cell_num < num_cells) {
uint32_t key_at_index = *leaf_node_key(node, cursor->cell_num);
if (key_at_index == key_to_insert) {
return EXECUTE_DUPLICATE_KEY;
}
}
// 插入数据
leaf_node_insert(cursor, row_to_insert->id, row_to_insert);
// 释放游标
free(cursor);
return EXECUTE_SUCCESS;
}
// 根据键返回游标
// table: 表
// key: 键值
Cursor* table_find(Table* table, uint32_t key)
{
uint32_t root_page_num = table->root_page_num;
void* root_node = get_page(table->pager, root_page_num);
if (get_node_type(root_node) == NODE_LEAF) {
return leaf_node_find(table, root_page_num, key);
}
else {
return internal_node_find(table, root_page_num, key);
}
return NULL;
}
// 返回游标
// page_num: 第几页
// key: 键值
Cursor* leaf_node_find(Table* table, uint32_t page_num, uint32_t key)
{
void* node = get_page(table->pager, page_num);
uint32_t num_cells = *leaf_node_num_cells(node);
Cursor* cursor = malloc(sizeof(Cursor));
cursor->table = table;
cursor->page_num = page_num;
// 二分查找找到键的位置
uint32_t min_index = 0;
uint32_t one_past_max_index = num_cells;
while(one_past_max_index != min_index) {
uint32_t index = min_index + (one_past_max_index - min_index) / 2;
uint32_t key_at_index = *leaf_node_key(node, index);
if (key == key_at_index) {
cursor->cell_num = index;
return cursor;
}
if (key < key_at_index) {
one_past_max_index = index;
}
else {
min_index = index + 1;
}
}
cursor->cell_num = min_index;
printf("leaf_node_find cursor page_num:%d cell_num:%d\n", page_num, min_index);
return cursor;
}
Cursor* internal_node_find(Table* table, uint32_t page_num, uint32_t key)
{
void* node = get_page(table->pager, page_num);
uint32_t num_keys = *internal_node_num_keys(node);
uint32_t min_index = 0;
uint32_t max_index = num_keys; // 子节点比键多1
while (min_index != max_index) {
uint32_t index = min_index + (max_index - min_index) / 2;
uint32_t key_to_right = *internal_node_key(node, index);
if (key_to_right >= key) {
max_index = index;
} else {
min_index = index + 1;
}
}
uint32_t child_num = *internal_node_child(node, min_index);
void* child = get_page(table->pager, child_num);
switch (get_node_type(child)) {
case NODE_LEAF:
return leaf_node_find(table, child_num, key);
break;
case NODE_INTERNAL:
return internal_node_find(table, child_num, key);
break;
default:
break;
}
return NULL;
}
// 打印数据
void print_row(Row* row)
{
printf("(%d %s %s)\n", row->id, row->username, row->email);
}
// 打印常量
void print_constants()
{
printf("uint8_t: %lu\n", sizeof(uint8_t));
printf("uint32_t: %lu\n", sizeof(uint32_t));
printf("ROW_SIZE: %d\n", ROW_SIZE);
printf("COMMON_NODE_HEADER_SIZE: %d\n", COMMON_NODE_HEADER_SIZE);
printf("LEAF_NODE_HEADER_SIZE: %d\n", LEAF_NODE_HEADER_SIZE);
printf("LEAF_NODE_CELL_SIZE: %d\n", LEAF_NODE_CELL_SIZE);
printf("LEAF_NODE_SPACE_FOR_CELLS: %d\n", LEAF_NODE_SPACE_FOR_CELLS);
printf("LEAF_NODE_MAX_CELLS: %d\n", LEAF_NODE_MAX_CELLS);
printf("INTERNAL_NODE_HEADER_SIZE %d\n", INTERNAL_NODE_HEADER_SIZE);
printf("INTERNAL_NODE_CELL_SIZE %d\n", INTERNAL_NODE_CELL_SIZE);
}
// 打印叶节点
void print_leaf_node(void* node)
{
uint32_t num_cells = *leaf_node_num_cells(node);
printf("leaf (size %d)\n", num_cells);
for (uint32_t i = 0; i < num_cells; i++) {
uint32_t key = *leaf_node_key(node, i);
printf(" - %d : %d\n", i, key);
}
}
// 打印进度
void indent(uint32_t level)
{
for (uint32_t i = 0; i < level; i++) {
printf(" ");
}
}
// 打印数据
void print_tree(Pager* pager, uint32_t page_num, uint32_t indentation_level)
{
void* node = get_page(pager, page_num);
uint32_t num_keys, child;
switch (get_node_type(node)) {
case (NODE_LEAF):
num_keys = *leaf_node_num_cells(node);
indent(indentation_level);
printf("- leaf (size %d)\n", num_keys);
for (uint32_t i = 0; i < num_keys; i++) {
indent(indentation_level + 1);
printf("- %d\n", *leaf_node_key(node, i));
}
break;
case (NODE_INTERNAL):
num_keys = *internal_node_num_keys(node);
indent(indentation_level);
printf("- internal (size %d)\n", num_keys);
for (uint32_t i = 0; i < num_keys; i++) {
child = *internal_node_child(node, i);
print_tree(pager, child, indentation_level + 1);
indent(indentation_level + 1);
printf("- key %d\n", *internal_node_key(node, i));
}
child = *internal_node_right_child(node);
print_tree(pager, child, indentation_level + 1);
break;
}
}
// 获取数据
ExecuteResult execute_select(Statement* statement, Table* table)
{
Cursor* cursor = table_start(table);
Row row;
while(!cursor->end_of_table) {
// 根据游标,反序列化
deserialize_row(cursor_value(cursor), &row);
// 打印
print_row(&row);
// 移动游标
cursor_advance(cursor);
}
free(cursor);
return EXECUTE_SUCCESS;
}
// 从文件中读取数据到内存
// filename: 文件名
Pager* pager_open(const char* filename)
{
// 1. 打开文件
int fd = open(filename,
O_RDWR | O_CREAT,
S_IWUSR | S_IRUSR
); // S_IWUSR 00200 user has write permission, 00400 user has read permission
if (fd == -1) {
printf("Unable to open file\n");
exit(EXIT_FAILURE);
}
// 2. 移动到文件尾
off_t file_length = lseek(fd, 0, SEEK_END);
printf("pager_open file length:%lld\n", file_length);
// 整页保存,大小只能为4k的倍数
if (file_length % PAGE_SIZE != 0) {
printf("Db file is not a whole number of pages. Corrupt file.\n");
exit(EXIT_FAILURE);
}
// 3. 初始化分页器
Pager* pager = malloc(sizeof(Pager));
pager->file_descriptor = fd;
pager->file_length = file_length;
pager->num_pages = (file_length / PAGE_SIZE);
for (uint32_t i = 0; i < TABLE_MAX_PAGES; i++) {
pager->pages[i] = NULL;
}
return pager;
}
// 打开数据库
// 1、打开文件,初始化分页器
// 2、使用分页器初始化表
// filename: 文件名
Table* db_open(const char* filename)
{
// 从文件中初始化分页器
Pager* pager = pager_open(filename);
Table* table = malloc(sizeof(Table));
table->pager = pager;
table->root_page_num = 0;
if(pager->num_pages == 0) {
void* root_node = get_page(pager, 0);
initialize_leaf_node(root_node);
set_node_root(root_node, true);
}
return table;
}
// 将分页器数据存入磁盘
// pager: 分页器
// page_num: 第几页
void pager_flush(Pager* pager, uint32_t page_num)
{
printf("pager_flush page_num:%d\n", page_num);
// 1. 判断数据是否为空
if(pager->pages[page_num] == NULL) {
printf("Tried to flush null page\n");
exit(EXIT_FAILURE);
}
// 2. 移动到第n页头
off_t offset = lseek(pager->file_descriptor, page_num * PAGE_SIZE, SEEK_SET);
if (offset == -1) {
printf("Error seeking: %d\n", errno);
exit(EXIT_FAILURE);
}
// 3. 写入数据
ssize_t bytes_written = write(pager->file_descriptor, pager->pages[page_num], PAGE_SIZE);
if (bytes_written == -1) {
printf("Error writing: %d\n", errno);
exit(EXIT_FAILURE);
}
}
// 释放表
// table:表
void free_table(Table* table)
{
for (uint32_t i = 0; i < TABLE_MAX_ROWS; i ++) {
free(table->pager->pages);
}
free(table->pager);
free(table);
}
// 根据类型执行操作
ExecuteResult execute_statement(Statement* statement, Table* table)
{
switch(statement->type) {
case (STATEMENT_INSERT):
printf("This is where we would do an insert.\n");
printf("> insert %d %s %s\n", statement->row_to_insert.id, statement->row_to_insert.username, statement->row_to_insert.email);
return execute_insert(statement, table);
break;
case (STATEMENT_SELECT):
printf("This is where we would do a select.\n");
return execute_select(statement, table);
break;
}
}
// 创建开始游标
Cursor* table_start(Table* table)
{
Cursor* cursor = table_find(table, 0);
void* node = get_page(table->pager, cursor->page_num);
uint32_t num_cells = *leaf_node_num_cells(node);
cursor->end_of_table = (num_cells == 0);
return cursor;
}
// 创建结束游标
Cursor* table_end(Table* table)
{
Cursor* cursor = malloc(sizeof(Cursor));
cursor->table = table;
cursor->page_num = table->root_page_num;
void* root_node = get_page(table->pager, table->root_page_num);
uint32_t num_cells = *leaf_node_num_cells(root_node);
cursor->cell_num = num_cells;
cursor->end_of_table = true;
return cursor;
}
// 向前移动游标
void cursor_advance(Cursor* cursor)
{
uint32_t page_num = cursor->page_num;
void* node = get_page(cursor->table->pager, page_num);
cursor->cell_num += 1;
if (cursor->cell_num >= (*leaf_node_num_cells(node))) {
// 移动到下一个兄弟叶子节点
uint32_t next_page_num = *leaf_node_next_leaf(node);
if (next_page_num == 0) {
// 最右边节点
cursor->end_of_table = true;
}
else {
cursor->page_num = next_page_num;
cursor->cell_num = 0;
}
}
}
// 叶子节点单元的数量
// node: 节点
uint32_t* leaf_node_num_cells(void* node)
{
return node + LEAF_NODE_NUM_CELLS_OFFSET;
}
// 获取单元
// node: 节点
// cell_num: 第几个cell
void* leaf_node_cell(void* node, uint32_t cell_num)
{
return node + LEAF_NODE_HEADER_SIZE + cell_num * LEAF_NODE_CELL_SIZE;
}
// 获取页节点键
// node: 节点
// cell_num: 第几个cell
uint32_t* leaf_node_key(void* node, uint32_t cell_num)
{
return leaf_node_cell(node, cell_num);
}
// 获取页节点数据
// node: 节点
// cell_num: 第几个cell
void* leaf_node_value(void* node, uint32_t cell_num)
{
return leaf_node_cell(node, cell_num) + LEAF_NODE_KEY_SIZE;
}
// 初始化叶子节点
// 1. 设置节点类型
// 2. 设置为非根节点
// 3. 重置单元数
// 4. 重置下一个兄弟节点
// node: 节点
void initialize_leaf_node(void* node)
{
set_node_type(node, NODE_LEAF);
set_node_root(node, false);
*leaf_node_num_cells(node) = 0;
*leaf_node_next_leaf(node) = 0; // 0 表示没有兄弟节点
}
// 初始化内部节点
// 1、设置节点类型
// 2、设置为非根节点
// 3、重置键数
// node: 节点
void initialize_internal_node(void* node)
{
set_node_type(node, NODE_INTERNAL);
set_node_root(node, false);
*internal_node_num_keys(node) = 0;
}
// 是否是根节点
// node: 节点
bool is_node_root(void* node)
{
uint8_t value = *((uint8_t*)(node + IS_ROOT_OFFSET));
return (bool)value;
}
// 设置是否是根节点
// node: 节点
// is_root: 是否是根节点
void set_node_root(void* node, bool is_root)
{
uint8_t value = is_root;
*((uint8_t*)(node + IS_ROOT_OFFSET)) = value;
}
// 获取页类型
// node: 节点
NodeType get_node_type(void* node)
{
uint8_t value = *((uint8_t *)(node + NODE_TYPE_OFFSET));
return (NodeType)value;
}
// 设置页类型
// node: 节点
// type: 类型
void set_node_type(void* node, NodeType type)
{
uint8_t value = type;
*((uint8_t *)(node + NODE_TYPE_OFFSET)) = value;
}
// 获取下一个兄弟页节点
// node: 节点
uint32_t* leaf_node_next_leaf(void* node)
{
return node + LEAF_NODE_NEXT_LEAF_OFFSET;
}
// 内部节点键的数量
// node: 节点
uint32_t* internal_node_num_keys(void* node)
{
return node + INTERNAL_NODE_NUM_KEYS_OFFSET;
}
// 内部节点右节点
// node: 节点
uint32_t* internal_node_right_child(void* node)
{
return node + INTERNAL_NODE_RIGHT_CHILD_OFFSET;
}
// 内部节点单元
// node: 节点
// cell_num: 第几个cell
uint32_t* internal_node_cell(void* node, uint32_t cell_num)
{
return node + INTERNAL_NODE_HEADER_SIZE + cell_num * INTERNAL_NODE_CELL_SIZE;
}
// 内部节点子节点
// node: 节点
// child_num: 子节点序号
uint32_t* internal_node_child(void* node, uint32_t child_num)
{
uint32_t num_keys = *internal_node_num_keys(node);
if (child_num > num_keys) {
printf("Tried to access child_num %d > num_keys %d\n", child_num, num_keys);
exit(EXIT_FAILURE);
} else if (child_num == num_keys) {
return internal_node_right_child(node);
} else {
return internal_node_cell(node, child_num);
}
}
// 叶节点插入
// cursor: 游标
// key: 键
// value: 数据
void leaf_node_insert(Cursor* cursor, uint32_t key, Row* value) {
// 1. 获取页
void* node = get_page(cursor->table->pager, cursor->page_num);
// 2. 判断是否满,满了则拆分页并插入
uint32_t num_cells = *leaf_node_num_cells(node);
printf("leaf_node_insert cursor page_num: %d, cell_num: %d num_cells:%d key:%d\n", cursor->page_num, cursor->cell_num, num_cells, key);
if (num_cells >= LEAF_NODE_MAX_CELLS) {
leaf_node_split_and_insert(cursor, key, value);
return;
}
// 3. 如果是中间插入,数据往后移动,腾出空间
if (cursor->cell_num < num_cells) {
for (uint32_t i = num_cells; i > cursor->cell_num; i--) {
memcpy(leaf_node_cell(node, i), leaf_node_cell(node, i-1), LEAF_NODE_CELL_SIZE);
}
}
// 4. 插入数据
// a. 数量加1
// b. 插入键
// c. 插入值
*(leaf_node_num_cells(node)) += 1;
*(leaf_node_key(node, cursor->cell_num)) = key;
serialize_row(value, leaf_node_value(node, cursor->cell_num));
}
// 节点满后,平分为两个节点
// cursor: 游标
// key: 键
// value: 数据
void leaf_node_split_and_insert(Cursor* cursor, uint32_t key, Row* value)
{
// 1.根据游标获取老节点
// 2.创建新节点
void* old_node = get_page(cursor->table->pager, cursor->page_num);
uint32_t new_page_num = get_unused_page_num(cursor->table->pager);
void* new_node = get_page(cursor->table->pager, new_page_num);
initialize_leaf_node(new_node);
*leaf_node_next_leaf(new_node) = *leaf_node_next_leaf(old_node);
*leaf_node_next_leaf(old_node) = new_page_num;
// 把将要插入的数据算入,共循环N+1
// N = 6
// LEAF = (N + 1) - RIGHT = 4
// RIGHT = (N + 1) / 2 = 3
// | left | right |
// 0,1,2,3, 4,5,6
//
// 注意 这里一定是 int 型而不是 uint型
for(int32_t i = LEAF_NODE_MAX_CELLS; i >=0; i--) {
void* destination_node;
if (i >= LEAF_NODE_LEFT_SPLIT_COUNT) {
destination_node = new_node;
}
else {
destination_node = old_node;
}
uint32_t index_within_node = i % LEAF_NODE_LEFT_SPLIT_COUNT; // 左边 >= 右边
void* destination = leaf_node_cell(destination_node, index_within_node);
if (i == cursor->cell_num) {
serialize_row(value, leaf_node_value(destination_node, index_within_node));
*leaf_node_key(destination_node, index_within_node) = key;
}
else if (i > cursor->cell_num) {
memcpy(destination, leaf_node_cell(old_node, i-1), LEAF_NODE_CELL_SIZE);
}
else {
memcpy(destination, leaf_node_cell(old_node, i), LEAF_NODE_CELL_SIZE);
}
}
// 更新节点单元数
*(leaf_node_num_cells(old_node)) = LEAF_NODE_LEFT_SPLIT_COUNT;
*(leaf_node_num_cells(new_node)) = LEAF_NODE_RIGHT_SPLIT_COUNT;
if (is_node_root(old_node)) {
return create_new_root(cursor->table, new_page_num);
}
else {
printf("Need to implemnet updating parent after split\n");
exit(EXIT_FAILURE);
}
}
// 处理分离根节点,左为根节点,右为新节点
// 拷贝老的根节点到新的左节点
// 初始化根节点为新的根节点
// 新的根节点指向两个子节点
// table: 表
// right_child_page_num: 右节点num
void create_new_root(Table* table, uint32_t right_child_page_num)
{
// 获取根节点,创建左节点
void* root = get_page(table->pager, table->root_page_num);
void* right_child = get_page(table->pager, right_child_page_num);
uint32_t left_child_page_num = get_unused_page_num(table->pager);
void* left_child = get_page(table->pager, left_child_page_num);
// 拷贝根节点数据到左节点
memcpy(left_child, root, PAGE_SIZE);
set_node_root(left_child, false);
// 根节点包含一个键和两个子节点
initialize_internal_node(root);
set_node_root(root, true);
*internal_node_num_keys(root) = 1; // 内部节点的键数为1
*internal_node_child(root, 0) = left_child_page_num; // 左节点存入内部节点体的第一个位置
uint32_t left_child_max_key = get_node_max_key(left_child); // 左节点最大键存入内部节点体的第一个位置
*internal_node_key(root, 0) = left_child_max_key;
*internal_node_right_child(root) = right_child_page_num; // 内部节点头部保存最右边的子节点
}
// 获取节点最大键值
// 内部节点:
// 叶子节点:
// node: 节点
uint32_t get_node_max_key(void* node)
{
// 因为是排好序的,所以最后一个即最大的键值
switch (get_node_type(node))
{
case NODE_INTERNAL:
return *internal_node_key(node, *internal_node_num_keys(node) - 1);
break;
case NODE_LEAF:
return *leaf_node_key(node, *leaf_node_num_cells(node) - 1);
break;
default:
break;
}
}
// 内部节点键
// node: 节点
// key_num: 第几个key
uint32_t* internal_node_key(void* node, uint32_t key_num)
{
return internal_node_cell(node, key_num) + INTERNAL_NODE_CHILD_SIZE;
}
// 获取未使用的页数
uint32_t get_unused_page_num(Pager* pager)
{
return pager->num_pages;
}
int main(int argc, char* argv[])
{
Table* table = db_open("sqlite.db");
InputBuffer* input_buffer = new_input_buffer();
while (true) {
print_prompt();
read_input(input_buffer);
if (input_buffer->buffer[0] == '.') {
switch(do_meta_command(input_buffer, table)) {
case (META_COMMAND_SUCCESS):
continue;
case (META_COMMAND_UNRECOGNIZED_COMMAND):