PostgreSQL的prepare 和 execute 动作背后

我给PostgreSQL的源代码加入了调试信息以后，会有如下表现：

我执行Prepare：

postgres=# prepare s(int) as select * from tst01 t where id < $;

PREPARE

postgres=# 

背后的反应：

** In PostgresMain

In exec_simple_query loop for parsetree_list++++++++++++++++++++++++++Before pg_plan_queries

***************In pg_plan_queries -------start

................In pg_plan_queries...query->commandType == CMD_UTILITY

***************In pg_plan_queries -------end

In exec_simple_query loop for parsetree_list++++++++++++++++++++++++++After pg_plan_queries

...In exec_simple_query....Before PortalRun

.....In PortalRun ------------start

.......In PortalRunUtility ---------------start

.........In ProcessUtility----Start

.........In ProcessUtility----End

.......In PortalRunUtility ---------------end

.....In PortalRun ------------end

...In exec_simple_query....After PortalRun

接着执行 Execute:

postgres=# execute s();

 id

----

( row)

postgres=# 

背后的反应：

In exec_simple_query loop for parsetree_list++++++++++++++++++++++++++Before pg_plan_queries

***************In pg_plan_queries -------start

................In pg_plan_queries...query->commandType == CMD_UTILITY

***************In pg_plan_queries -------end

In exec_simple_query loop for parsetree_list++++++++++++++++++++++++++After pg_plan_queries

...In exec_simple_query....Before PortalRun

.....In PortalRun ------------start

xxxxxxIn FillPortalStore ...........start

.......In PortalRunUtility ---------------start

.........In ProcessUtility----Start

..........In standard_ProcessUtility ... Before ExecuteQuery

xxxxxxxxxxxIn ExecuteQuery--------start

++++++++++++In GetCachedPlan ........start

.............In BuildCachedPlan, Before pg_plan_queries

***************In pg_plan_queries -------start

................In pg_plan_queries...query->commandType != CMD_UTILITY

..................In pg_plan_query........start

*******************In planner ........start

___________________In standard_planner........start

********************In subquery_planner........start

++++++++++++++++++++++In grouping_planner......start

************************In query_planner......start

........................In make_one_rel......start

...........................In set_base_rel_pathlists......start

-----------------------------In set_rel_pathlist......start

******************************In set_plain_rel_pathlist......start

-------------------------------Before add_path of seqscan

-------------------------------After add_path of seqscan

-------------------------------Before create_index_paths

-------------------------------After create_index_path

-------------------------------Before create_tidscan_paths

-------------------------------After create_tidscan_paths

-------------------------------Before set_cheapest

-------------------------------After set_cheapest

******************************In set_plain_rel_pathlist......end

-----------------------------In set_rel_pathlist......end

...........................In set_base_rel_pathlists......end

........................In make_one_rel......end

************************In query_planner......end

++++++++++++++++++++++In grouping_planner......end

********************In subquery_planner........end

___________________In standard_planner........end

*******************In planner ........end

..................In pg_plan_query........end

***************In pg_plan_queries -------end

.............In BuildCachedPlan, After pg_plan_queries

++++++++++++In GetCachedPlan ........end

.....In PortalRun ------------start

.....In PortalRun ------------end

xxxxxxxxxxxIn ExecuteQuery--------end

..........In standard_ProcessUtility ... After ExecuteQuery

.........In ProcessUtility----End

.......In PortalRunUtility ---------------end

xxxxxxIn FillPortalStore ...........end

.....In PortalRun ------------end

...In exec_simple_query....After PortalRun

按照对过去版本的认识，应当是PortalRun的时候单纯执行计划。

但是preapre....execute 方式，把它破坏了。

可以看到，prepare时候，不进行path的生成。

execute 的时候，在PortalRun的阶段，通过 ExecuteQuery->GetCachedPlan->BuildCachedPlan，

来生成path和确定plan。

不过要注意到一点是，我所执行的上述的例子中，并没有导致 param_info 非空。

可以说，这种针对单一表的preapre execute，是把执行计划的生成推后了，但是并不等于它就是 Parameterized Path。