如何给MySQL添加自定义语法的方法示例(2)-木庄网络博客

sql/parse_tree_nodes.cc sql/parse_tree_nodes.h sql/parse_tree_partitions.cc sql/parse_tree_partitions.h

四个文件里，理论上可以放在任何地方。可根据自身需求添加对应数据结构：

文件：sql/parse_tree_partitions.h sql/parse_tree_partitions.cc

/**
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;
}

文件：sql/parse_tree_nodes.cc sql/parse_tree_nodes.h

接下来修改create table对应的数据结构，将新增的PT_global_partition添加到create table里面

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<PT_table_element *> *opt_table_element_list,
    const Mem_root_array<PT_create_table_option *> *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;
    }
}

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