mysql insert执行过程_MySQL · 源码分析 · 一条insert语句的执行过程-阿里云开发者社区...

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 &fields, /* insert 的字段 */ List &values_list, /* insert 的值 */ List &update_fields,

List &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