Author: xijia
本文只分析了insert语句执行的主路径，和路径上部分关键函数，很多细节没有深入，留给读者继续分析
create table t1(id int);
insert into t1 values(1)
略过建立连接，从 mysql_parse() 开始分析
void mysql_parse(THD *thd, char *rawbuf, uint length,
Parser_state *parser_state)
{
/* ...... */
/* 检查query_cache，如果结果存在于cache中，直接返回 */
if (query_cache_send_result_to_client(thd, rawbuf, length) <= 0)
{
LEX *lex= thd->lex;
/* 解析语句 */
bool err= parse_sql(thd, parser_state, NULL);
/* 整理语句格式，记录 general log */
/* ...... */
/* 执行语句 */
error= mysql_execute_command(thd);
/* 提交或回滚没结束的事务（事务可能在mysql_execute_command中提交，用trx_end_by_hint标记事务是否已经提交） */
if (!thd->trx_end_by_hint)
{
if (!error && lex->ci_on_success)
trans_commit(thd);
if (error && lex->rb_on_fail)
trans_rollback(thd);
}
进入 mysql_execute_command()
/* */
/* ...... */
case SQLCOM_INSERT:
{
/* 检查权限 */
if ((res= insert_precheck(thd, all_tables)))
break;
/* 执行insert */
res= mysql_insert(thd, all_tables, lex->field_list, lex->many_values,
lex->update_list, lex->value_list,
lex->duplicates, lex->ignore);
/* 提交或者回滚事务 */
if (!res)
{
trans_commit_stmt(thd);
trans_commit(thd);
thd->trx_end_by_hint= TRUE;
}
else if (res)
{
trans_rollback_stmt(thd);
trans_rollback(thd);
thd->trx_end_by_hint= TRUE;
}
进入 mysql_insert()
bool mysql_insert(THD *thd,TABLE_LIST *table_list,
List<Item> &fields, /* insert 的字段 */
List<List_item> &values_list, /* insert 的值 */
List<Item> &update_fields,
List<Item> &update_values,
enum_duplicates duplic,
bool ignore)
{
/*对每条记录调用 write_record */
while ((values= its++))
{
if (lock_type == TL_WRITE_DELAYED)
{
LEX_STRING const st_query = { query, thd->query_length() };
DEBUG_SYNC(thd, "before_write_delayed");
/* insert delay */
error= write_delayed(thd, table, st_query, log_on, &info);
DEBUG_SYNC(thd, "after_write_delayed");
query=0;
}
else
/* normal insert */
error= write_record(thd, table, &info, &update);
}
/*
这里还有
thd->binlog_query()写binlog
my_ok()返回ok报文，ok报文中包含影响行数
*/
进入 write_record
/*
COPY_INFO *info 用来处理唯一键冲突，记录影响行数
COPY_INFO *update 处理 INSERT ON DUPLICATE KEY UPDATE 相关信息
*/
int write_record(THD *thd, TABLE *table, COPY_INFO *info, COPY_INFO *update)
{
if (duplicate_handling == DUP_REPLACE || duplicate_handling == DUP_UPDATE)
{
/* 处理 INSERT ON DUPLICATE KEY UPDATE 等复杂情况 */
}
/* 调用存储引擎的接口 */
else if ((error=table->file->ha_write_row(table->record[0])))
{
DEBUG_SYNC(thd, "write_row_noreplace");
if (!ignore_errors ||
table->file->is_fatal_error(error, HA_CHECK_DUP))
goto err;
table->file->restore_auto_increment(prev_insert_id);
goto ok_or_after_trg_err;
}
}
进入ha_write_row、write_row
/* handler 是各个存储引擎的基类，这里我们使用InnoDB引擎*/
int handler::ha_write_row(uchar *buf)
{
/* 指定log_event类型*/
Log_func *log_func= Write_rows_log_event::binlog_row_logging_function;
error= write_row(buf);
}
进入引擎层，这里是innodb引擎，handler对应ha_innobase 插入的表信息保存在handler中
int
ha_innobase::write_row(
/*===================*/
uchar* record) /*!< in: a row in MySQL format */
{
error = row_insert_for_mysql((byte*) record, prebuilt);
}
UNIV_INTERN
dberr_t
row_insert_for_mysql(
/*=================*/
byte* mysql_rec, /*!< in: row in the MySQL format */
row_prebuilt_t* prebuilt) /*!< in: prebuilt struct in MySQL
handle */
{
/*记录格式从MySQL转换成InnoDB*/
row_mysql_convert_row_to_innobase(node->row, prebuilt, mysql_rec);
thr->run_node = node;
thr->prev_node = node;
/*插入记录*/
row_ins_step(thr);
}
UNIV_INTERN
que_thr_t*
row_ins_step(
/*=========*/
que_thr_t* thr) /*!< in: query thread */
{
/*给表加IX锁*/
err = lock_table(0, node->table, LOCK_IX, thr);
/*插入记录*/
err = row_ins(node, thr);
}
InnoDB表是基于B+树的索引组织表
如果InnoDB表没有主键和唯一键，需要分配隐含的row_id组织聚集索引
row_id分配逻辑在row_ins中，这里不详细展开
static __attribute__((nonnull, warn_unused_result))
dberr_t
row_ins(
/*====*/
ins_node_t* node, /*!< in: row insert node */
que_thr_t* thr) /*!< in: query thread */
{
if (node->state == INS_NODE_ALLOC_ROW_ID) {
/*若innodb表没有主键和唯一键，用row_id组织索引*/
row_ins_alloc_row_id_step(node);
/*获取row_id的索引*/
node->index = dict_table_get_first_index(node->table);
node->entry = UT_LIST_GET_FIRST(node->entry_list);
}
/*遍历所有索引，向每个索引中插入记录*/
while (node->index != NULL) {
if (node->index->type != DICT_FTS) {
/* 向索引中插入记录 */
err = row_ins_index_entry_step(node, thr);
if (err != DB_SUCCESS) {
return(err);
}
}
/*获取下一个索引*/
node->index = dict_table_get_next_index(node->index);
node->entry = UT_LIST_GET_NEXT(tuple_list, node->entry);
}
}
}
插入单个索引项
static __attribute__((nonnull, warn_unused_result))
dberr_t
row_ins_index_entry_step(
/*=====================*/
ins_node_t* node, /*!< in: row insert node */
que_thr_t* thr) /*!< in: query thread */
{
dberr_t err;
/*给索引项赋值*/
row_ins_index_entry_set_vals(node->index, node->entry, node->row);
/*插入索引项*/
err = row_ins_index_entry(node->index, node->entry, thr);
return(err);
}
static
dberr_t
row_ins_index_entry(
/*================*/
dict_index_t* index, /*!< in: index */
dtuple_t* entry, /*!< in/out: index entry to insert */
que_thr_t* thr) /*!< in: query thread */
{
if (dict_index_is_clust(index)) {
/* 插入聚集索引 */
return(row_ins_clust_index_entry(index, entry, thr, 0));
} else {
/* 插入二级索引 */
return(row_ins_sec_index_entry(index, entry, thr));
}
}
row_ins_clust_index_entry 和 row_ins_sec_index_entry 函数结构类似，只分析插入聚集索引
UNIV_INTERN
dberr_t
row_ins_clust_index_entry(
/*======================*/
dict_index_t* index, /*!< in: clustered index */
dtuple_t* entry, /*!< in/out: index entry to insert */
que_thr_t* thr, /*!< in: query thread */
ulint n_ext) /*!< in: number of externally stored columns */
{
if (UT_LIST_GET_FIRST(index->table->foreign_list)) {
err = row_ins_check_foreign_constraints(
index->table, index, entry, thr);
if (err != DB_SUCCESS) {
return(err);
}
}
/* flush log，make checkpoint（如果需要） */
log_free_check();
/* 先尝试乐观插入，修改叶子节点 BTR_MODIFY_LEAF */
err = row_ins_clust_index_entry_low(
0, BTR_MODIFY_LEAF, index, n_uniq, entry, n_ext, thr,
&page_no, &modify_clock);
if (err != DB_FAIL) {
DEBUG_SYNC_C("row_ins_clust_index_entry_leaf_after");
return(err);
}
/* flush log，make checkpoint（如果需要） */
log_free_check();
/* 乐观插入失败，尝试悲观插入 BTR_MODIFY_TREE */
return(row_ins_clust_index_entry_low(
0, BTR_MODIFY_TREE, index, n_uniq, entry, n_ext, thr,
&page_no, &modify_clock));
row_ins_clust_index_entry_low 和 row_ins_sec_index_entry_low 函数结构类似，只分析插入聚集索引
UNIV_INTERN
dberr_t
row_ins_clust_index_entry_low(
/*==========================*/
ulint flags, /*!< in: undo logging and locking flags */
ulint mode, /*!< in: BTR_MODIFY_LEAF or BTR_MODIFY_TREE,
depending on whether we wish optimistic or
pessimistic descent down the index tree */
dict_index_t* index, /*!< in: clustered index */
ulint n_uniq, /*!< in: 0 or index->n_uniq */
dtuple_t* entry, /*!< in/out: index entry to insert */
ulint n_ext, /*!< in: number of externally stored columns */
que_thr_t* thr, /*!< in: query thread */
ulint* page_no,/*!< *page_no and *modify_clock are used to decide
whether to call btr_cur_optimistic_insert() during
pessimistic descent down the index tree.
in: If this is optimistic descent, then *page_no
must be ULINT_UNDEFINED. If it is pessimistic
descent, *page_no must be the page_no to which an
optimistic insert was attempted last time
row_ins_index_entry_low() was called.
out: If this is the optimistic descent, *page_no is set
to the page_no to which an optimistic insert was
attempted. If it is pessimistic descent, this value is
not changed. */
ullint* modify_clock) /*!< in/out: *modify_clock == ULLINT_UNDEFINED
during optimistic descent, and the modify_clock
value for the page that was used for optimistic
insert during pessimistic descent */
{
/* 将cursor移动到索引上待插入的位置 */
btr_cur_search_to_nth_level(index, 0, entry, PAGE_CUR_LE, mode,
&cursor, 0, __FILE__, __LINE__, &mtr);
/*根据不同的flag检查主键冲突*/
err = row_ins_duplicate_error_in_clust_online(
n_uniq, entry, &cursor,
&offsets, &offsets_heap);
err = row_ins_duplicate_error_in_clust(
flags, &cursor, entry, thr, &mtr);
/*
如果要插入的索引项已存在，则把insert操作改为update操作
索引项已存在，且没有主键冲突，是因为之前的索引项对应的数据被标记为已删除
本次插入的数据和上次删除的一样，而索引项并未删除，所以变为update操作
*/
if (row_ins_must_modify_rec(&cursor)) {
/* There is already an index entry with a long enough common
prefix, we must convert the insert into a modify of an
existing record */
mem_heap_t* entry_heap = mem_heap_create(1024);
/* 更新数据到存在的索引项 */
err = row_ins_clust_index_entry_by_modify(
flags, mode, &cursor, &offsets, &offsets_heap,
entry_heap, &big_rec, entry, thr, &mtr);
/*如果索引正在online_ddl，先记录insert*/
if (err == DB_SUCCESS && dict_index_is_online_ddl(index)) {
row_log_table_insert(rec, index, offsets);
}
/*提交mini transaction*/
mtr_commit(&mtr);
mem_heap_free(entry_heap);
} else {
rec_t* insert_rec;
if (mode != BTR_MODIFY_TREE) {
/*进行一次乐观插入*/
err = btr_cur_optimistic_insert(
flags, &cursor, &offsets, &offsets_heap,
entry, &insert_rec, &big_rec,
n_ext, thr, &mtr);
} else {
/*
如果buffer pool余量不足25%，插入失败，返回DB_LOCK_TABLE_FULL
处理DB_LOCK_TABLE_FULL错误时，会回滚事务
防止大事务的锁占满buffer pool(注释里写的)
*/
if (buf_LRU_buf_pool_running_out()) {
err = DB_LOCK_TABLE_FULL;
goto err_exit;
}
if (/*太长了，略*/) {
/*进行一次乐观插入*/
err = btr_cur_optimistic_insert(
flags, &cursor,
&offsets, &offsets_heap,
entry, &insert_rec, &big_rec,
n_ext, thr, &mtr);
} else {
err = DB_FAIL;
}
if (err == DB_FAIL) {
/*乐观插入失败，进行悲观插入*/
err = btr_cur_pessimistic_insert(
flags, &cursor,
&offsets, &offsets_heap,
entry, &insert_rec, &big_rec,
n_ext, thr, &mtr);
}
}
}
btr_cur_optimistic_insert 和 btr_cur_pessimistic_insert 涉及B+树的操作，内部细节很多，以后再做分析