如何给MySQL添加自定义语法的方法示例_Mysql_

create table t1 ( id int primary key, name varchar(100) ) global_partition by hash(id) partitions 10; //global_partition by为新增语法，global_partition为新增token 

sql/lex.h //token sql/parse_tree_nodes.cc sql/parse_tree_nodes.h sql/parse_tree_partitions.cc sql/parse_tree_partitions.h sql/parser_yystype.h sql/sql_yacc.yy 

static const SYMBOL symbols[] = { /* Insert new SQL keywords after that commentary (by alphabetical order): */ //省略部分代码 {SYM("GLOBAL_PARTITION", GLOBAL_PARTITION_SYM)}, //注意按照字典序进行添加。 //省略部分代码 }; 

%token GLOBAL_PARTITION_SYM 1309 /* seancheer */ //### 声明上一步添加的token，声明了才可以使用，编号1309选择一个未使用的就行 %type  global_partition_clause //### 声明新增加的数据结构，后面会介绍 create_table_stmt: CREATE opt_temporary TABLE_SYM opt_if_not_exists table_ident '(' table_element_list ')' opt_create_table_options_etc //最后一个标记在YYSTYPE中对应的是create_table_tail， 后面会介绍 { $$= NEW_PTN PT_create_table_stmt(YYMEM_ROOT, $1, $2, $4, $5, $7, $9.opt_create_table_options, $9.opt_partitioning, $9.opt_global_partitioning, //### 赋值给对应参数，该构造函数需要新增，后面会介绍 $9.on_duplicate, $9.opt_query_expression); } | CREATE opt_temporary TABLE_SYM opt_if_not_exists table_ident opt_create_table_options_etc { $$= NEW_PTN PT_create_table_stmt(YYMEM_ROOT, $1, $2, $4, $5, NULL, $6.opt_create_table_options, $6.opt_partitioning, $6.opt_global_partitioning, //### 赋值给对应参数，该构造函数需要新增，后面会介绍 $6.on_duplicate, $6.opt_query_expression); //partition相关的语法 opt_create_partitioning_etc: partition_clause opt_duplicate_as_qe //这里是原生的partition表语法 { $$= $2; $$.opt_partitioning= $1; } | global_partition_clause opt_duplicate_as_qe //### 此处是新增的global_partition语法， { $$= $2; $$.opt_global_partitioning= $1; } | opt_duplicate_as_qe ; //### 下面为重点，新增的global_partition语法，可以看到，用到了新增的token global_partition_clause: GLOBAL_PARTITION_SYM BY part_type_def opt_num_parts { $$= NEW_PTN PT_global_partition($3, @4, $4); } ; 

union YYSTYPE { PT_sub_partition *opt_sub_part; PT_part_type_def *part_type_def; PT_partition *partition_clause; PT_global_partition *global_partition_clause; //新加数据结构 struct { Mem_root_array *opt_create_table_options; PT_partition *opt_partitioning; PT_global_partition *opt_global_partitioning; //同时注意添加到create_table_tail里面，因为create table语法会有该操作 On_duplicate on_duplicate; PT_query_primary *opt_query_expression; } create_table_tail; }; static_assert(sizeof(YYSTYPE) <= 40, "YYSTYPE is too big"); //因为struct里面添加了一个成员变量，所以该union需要的空间也会变大，因此注意修改这一行 

/** 新增数据结构 */ class PT_global_partition : public Parse_tree_node { typedef Parse_tree_node super; PT_part_type_def *const part_type_def; const POS part_defs_pos; uint num_parts; public: partition_info part_info; public: PT_global_partition(PT_part_type_def *part_type_def, const POS &part_defs_pos, uint opt_num_parts) : part_type_def(part_type_def), part_defs_pos(part_defs_pos), num_parts(opt_num_parts) {} bool contextualize(Parse_context *pc) override; }; //模仿其原生的实现方式即可 bool PT_global_partition::contextualize(Parse_context *pc) { if (super::contextualize(pc)) return true; Partition_parse_context part_pc(pc->thd, &part_info, false); if (part_type_def->contextualize(&part_pc)) return true; if (part_info.part_type != partition_type::HASH) { //only support hash partition for shard key my_error(ER_PARTITIONS_MUST_BE_DEFINED_ERROR, MYF(0), "NOT HASH"); return true; } uint count_curr_parts = part_info.partitions.elements; if (part_info.num_parts != 0) { if (part_info.num_parts != count_curr_parts) { error(&part_pc, part_defs_pos, ER_THD(pc->thd, ER_PARTITION_WRONG_NO_PART_ERROR)); return true; } } else if (count_curr_parts > 0) part_info.num_parts = count_curr_parts; return false; } 

class PT_create_table_stmt final : public PT_table_ddl_stmt_base { PT_partition *opt_partitioning; PT_global_partition *opt_global_partitioning; //添加成员变量 PT_create_table_stmt( MEM_ROOT *mem_root, PT_hint_list *opt_hints, bool is_temporary, bool only_if_not_exists, Table_ident *table_name, const Mem_root_array *opt_table_element_list, const Mem_root_array *opt_create_table_options, PT_partition *opt_partitioning, PT_global_partition *opt_global_partitioning, On_duplicate on_duplicate, PT_query_primary *opt_query_expression) : PT_table_ddl_stmt_base(mem_root), m_opt_hints(opt_hints), is_temporary(is_temporary), only_if_not_exists(only_if_not_exists), table_name(table_name), opt_table_element_list(opt_table_element_list), opt_create_table_options(opt_create_table_options), opt_partitioning(opt_partitioning), opt_global_partitioning(opt_global_partitioning), //添加构造函数，主要是为了增加对PT_global_partition的赋值操作 on_duplicate(on_duplicate), opt_query_expression(opt_query_expression), opt_like_clause(nullptr) {} //在其对应的函数中增加相关逻辑，调用对应的初始化函数contextualize Sql_cmd *PT_create_table_stmt::make_cmd(THD *thd) { if (opt_global_partitioning){ if (opt_global_partitioning->contextualize(&pc)) return nullptr; lex->part_info = &opt_global_partitioning->part_info; } }