postgresql SQL 的相关内容

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之四十七

再次上溯： /*-------------------- * subquery_planner * Invokes the planner on a subquery. We recurse to here for each * sub-SELECT found in the query tree. * * glob is the global state f...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之四十九

接前面，继续对 subquery_planner来分析：下面这一段都是对表达式进行处理的，对我的简单查询，可以忽略。 /* * Do expression preprocessing on targetlist and quals, as well as other * random expressions in the querytree. Note th...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十一

继续分析 query_planner： /* * query_planner * Generate a path (that is, a simplified plan) for a basic query, * which may involve joins but not any fancier features. * * Since query_plann...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十四

接前面，从 cheapeast_path 的角度，关注 query_planner 函数，对其进行简化： void query_planner(PlannerInfo *root, List *tlist, double tuple_fraction, double limit_tuples, Path **cheapest_path,...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十五

接前面。从 cheapest_total_path 来看： query_planner 会先调用 build_simple_rel，这里完成了 cheapest_total_path 的初始化。 (query_planner --> add_base_rels_to_query --> query_planner) 然后，query_planner 再在后面调...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十六

接前面，继续分析 : cheapest_startup_path = cheapest_total_path = NULL; have_parameterized_paths = false; foreach(p, parent_rel->pathlist) { Path *path = (Path *) lfirst(p)...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十七

接着追踪 ->pathlist：初始化可能是在这里完成的？ /* * add_path * Consider a potential implementation path for the specified parent rel, * and add it to the rel's pathlist if it is worthy of considera...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十九

由于用单纯的SQL语句来探查代码，看得还是不够清楚。所以我再采用如下的方法： postgres=# explain select dept.no_emps,emp.age from dept,emp where emp.name = dept.mgr and dept.dept_name = 'shoe'; QUERY PLAN ...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之六十一

对Join的成本计算的调用路径： make_one_rel ->make_rel_from_joinlist ->standard_join_search -> join_search_one_level ...

文章 2022-02-16 来自：开发者社区

PostgreSQL在何处处理 sql查询之六十二

对 RelOptInfo * make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) 函数进行研究：看看 inner join 时候发生的事情： RelOptInfo * make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) ...

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