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MySQL源碼分析之SQL函數(shù)執(zhí)行

1.MySQL中執(zhí)行一條SQL的總體流程

一條包含函數(shù)的SQL語句，在MySQL中會經(jīng)過: 客戶端發(fā)送，服務(wù)器連接，語法解析，語句執(zhí)行的過程。

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調(diào)試源碼，分析函數(shù)的具體執(zhí)行過程，在客戶端，執(zhí)行select to_char(‘test’) from dual。

跟蹤堆棧：pthread_start→handle_one_connection→do_handle_one_connect→do_command→dispatch_command，確定SQL函數(shù)的執(zhí)行入口為dispatch_command

調(diào)試跟蹤SQL內(nèi)部執(zhí)行過程為：

2.SQL函數(shù)執(zhí)行過程

分析堆棧信息，確定SQL函數(shù)主要執(zhí)行過程為：

SQL_PARSE 語法解析
SQL_RESOLVER prepare準(zhǔn)備執(zhí)行
SQL_EXCUTOR 具體執(zhí)行函數(shù)

SQL_PARSE堆棧：

1  To_char_instantiator::instantiate(To_char_instantiator * const this, THD * thd, PT_item_list * args) (/home/bob/work/percona-server/sql/item_create.cc:785)
2  (anonymous namespace)::Function_factory::create_func((anonymous namespace)::Function_factory * const this, THD * thd, LEX_STRING function_name, PT_item_list * item_list) (/home/bob/work/percona-server/sql/item_create.cc:1203)
3  PTI_function_call_generic_ident_sys::itemize(PTI_function_call_generic_ident_sys * const this, Parse_context * pc, Item ** res) (/home/bob/work/percona-server/sql/parse_tree_items.cc:259)
4  PTI_expr_with_alias::itemize(PTI_expr_with_alias * const this, Parse_context * pc, Item ** res) (/home/bob/work/percona-server/sql/parse_tree_items.cc:337)
5  PT_item_list::contextualize(PT_item_list * const this, Parse_context * pc) (/home/bob/work/percona-server/sql/parse_tree_helpers.h:112)
6  PT_select_item_list::contextualize(PT_select_item_list * const this, Parse_context * pc) (/home/bob/work/percona-server/sql/parse_tree_nodes.cc:3813)
7  PT_query_specification::contextualize(PT_query_specification * const this, Parse_context * pc) (/home/bob/work/percona-server/sql/parse_tree_nodes.cc:1551)
8  PT_query_expression::contextualize(PT_query_expression * const this, Parse_context * pc) (/home/bob/work/percona-server/sql/parse_tree_nodes.cc:4178)
9  PT_select_stmt::make_cmd(PT_select_stmt * const this, THD * thd) (/home/bob/work/percona-server/sql/parse_tree_nodes.cc:648)
10 LEX::make_sql_cmd(LEX * const this, Parse_tree_root * parse_tree) (/home/bob/work/percona-server/sql/sql_lex.cc:5237)
11 THD::sql_parser(THD * const this) (/home/bob/work/percona-server/sql/sql_class.cc:2978)
12 parse_sql(THD * thd, Parser_state * parser_state, Object_creation_ctx * creation_ctx) (/home/bob/work/percona-server/sql/sql_parse.cc:7333)
13 dispatch_sql_command(THD * thd, Parser_state * parser_state, bool update_userstat) (/home/bob/work/percona-server/sql/sql_parse.cc:5237)
14 dispatch_command(THD * thd, const COM_DATA * com_data, enum_server_command command) (/home/bob/work/percona-server/sql/sql_parse.cc:1978)
15 do_command(THD * thd) (/home/bob/work/percona-server/sql/sql_parse.cc:1426)
16 handle_connection(void * arg) (/home/bob/work/percona-server/sql/conn_handler/connection_handler_per_thread.cc:307)
17 pfs_spawn_thread(void * arg) (/home/bob/work/percona-server/storage/perfschema/pfs.cc:2899)
18 libpthread.so.0!start_thread(void * arg) (/build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477)
19 libc.so.6!clone() (/build/glibc-eX1tMB/glibc-2.31/sysdeps/unix/sysv/linux/x86_64/clone.S:95)

SQL_RESOLVER堆棧：

1  Item_func_to_char::resolve_type(Item_func_to_char * const this, THD * thd) (/home/bob/work/percona-server/sql/item_timefunc.cc:3821)
2  Item_func::fix_fields(Item_func * const this, THD * thd) (/home/bob/work/percona-server/sql/item_func.cc:309)
3  Item_str_func::fix_fields(Item_str_func * const this, THD * thd, Item ** ref) (/home/bob/work/percona-server/sql/item_strfunc.cc:161)
4  setup_fields(THD * thd, ulong want_privilege, bool allow_sum_func, bool split_sum_funcs, bool column_update, const mem_root_deque * typed_items, mem_root_deque * fields, Ref_item_array ref_item_array) (/home/bob/work/percona-server/sql/sql_base.cc:9216)
5  Query_block::prepare(Query_block * const this, THD * thd, mem_root_deque * insert_field_list) (/home/bo6 b/work/percona-server/sql/sql_resolver.cc:275)
7  Sql_cmd_select::prepare_inner(Sql_cmd_select * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_select.cc:467)
8  Sql_cmd_dml::prepare(Sql_cmd_dml * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_select.cc:389)
9  Sql_cmd_dml::execute(Sql_cmd_dml * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_select.cc:522)
10 mysql_execute_command(THD * thd, bool first_level) (/home/bob/work/percona-server/sql/sql_parse.cc:4740)
11 dispatch_sql_command(THD * thd, Parser_state * parser_state, bool update_userstat) (/home/bob/work/percona-server/sql/sql_parse.cc:5337)
12 dispatch_command(THD * thd, const COM_DATA * com_data, enum_server_command command) (/home/bob/work/percona-server/sql/sql_parse.cc:1978)
13 do_command(THD * thd) (/home/bob/work/percona-server/sql/sql_parse.cc:1426)
14 handle_connection(void * arg) (/home/bob/work/percona-server/sql/conn_handler/connection_handler_per_thread.cc:307)
15 pfs_spawn_thread(void * arg) (/home/bob/work/percona-server/storage/perfschema/pfs.cc:2899)
16 libpthread.so.0!start_thread(void * arg) (/build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477)
17 libc.so.6!clone() (/build/glibc-eX1tMB/glibc-2.31/sysdeps/unix/sysv/linux/x86_64/clone.S:95)

SQL_EXCUTOR 堆棧：

1  Item_func_to_char::val_str(Item_func_to_char * const this, String * str) (/home/bob/work/percona-server/sql/item_timefunc.cc:3915)
2  Item::send(Item * const this, Protocol * protocol, String * buffer) (/home/bob/work/percona-server/sql/item.cc:7025)
3  THD::send_result_set_row(THD * const this, const mem_root_deque & row_items) (/home/bob/work/percona-server/sql/sql_class.cc:2793)
4  Query_result_send::send_data(Query_result_send * const this, THD * thd, const mem_root_deque & items) (/home/bob/work/percona-server/sql/query_result.cc:100)
5  Query_expression::ExecuteIteratorQuery(Query_expression * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_union.cc:1249)
6  Query_expression::execute(Query_expression * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_union.cc:1287)
7  Sql_cmd_dml::execute_inner(Sql_cmd_dml * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_select.cc:791)
8  Sql_cmd_dml::execute(Sql_cmd_dml * const this, THD * thd) (/home/bob/work/percona-server/sql/sql_select.cc:575)
9  mysql_execute_command(THD * thd, bool first_level) (/home/bob/work/percona-server/sql/sql_parse.cc:4740)
10 dispatch_sql_command(THD * thd, Parser_state * parser_state, bool update_userstat) (/home/bob/work/percona-server/sql/sql_parse.cc:5337)
11 dispatch_command(THD * thd, const COM_DATA * com_data, enum_server_command command) (/home/bob/work/percona-server/sql/sql_parse.cc:1978)
12 do_command(THD * thd) (/home/bob/work/percona-server/sql/sql_parse.cc:1426)
13 handle_connection(void * arg) (/home/bob/work/percona-server/sql/conn_handler/connection_handler_per_thread.cc:307)
14 pfs_spawn_thread(void * arg) (/home/bob/work/percona-server/storage/perfschema/pfs.cc:2899)
15 libpthread.so.0!start_thread(void * arg) (/build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477)
16 libc.so.6!clone() (/build/glibc-eX1tMB/glibc-2.31/sysdeps/unix/sysv/linux/x86_64/clone.S:95)

SQL_PARSE： SQL解析生成AST語法的語法樹，to_char函數(shù)，實(shí)際中已解析為Item_func_to_char的語法樹節(jié)點(diǎn)。

SQL_RESOLVER：準(zhǔn)備階段prepare，初始化賦值，如Item_func_to_char::resolve_type設(shè)定函數(shù)轉(zhuǎn)換后的數(shù)據(jù)類型。

SQL_EXCUTOR：執(zhí)行階段，執(zhí)行to_char函數(shù)功能，通過Item_func_to_char::val_str，實(shí)際功能處理過程。

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1.MySQL中執(zhí)行一條SQL的總體流程

2.SQL函數(shù)執(zhí)行過程

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