postgresql SQL 的相关内容

文章 2017-12-27 来自：开发者社区

PostgreSQL在何处处理 sql查询之六十五

看hash join 里的概念： numbuckets与numbatches： numbuckets是在内存中，hash表里面，"桶"的个数。 numbatches是如果hash表过大，在内存中放不下，则要分多次进行。 void final_cost_hashjoin(PlannerInfo *root, HashPath *path, JoinC...

文章 2017-12-27 来自：开发者社区

PostgreSQL在何处处理 sql查询之二

在exec_simple_query中，代码如下： 1 /* 2 * exec_simple_query 3 * 4 * Execute a "simple Query" protocol message. 5 */ 6 static void 7 exec_simple_query(const char *query_string) 8 { 9 ...

文章 2017-12-26 来自：开发者社区

PostgreSQL在何处处理 sql查询之二十三

再次回到 estimate_rel_size 我发现，在入口参数 rel中， rel->rd_rel->reltuples 的值已经完全准备好了： /* * estimate_rel_size - estimate # pages and # tuples in a table or index * * We also estimate the fraction...

文章 2017-12-21 来自：开发者社区

PostgreSQL在何处处理 sql查询之五十

接前面： Query *parse = root->parse; List *tlist = parse->targetList; int64 offset_est = 0; int64 count_est = 0; double limit_tuples = -1.0; ...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之六十三

此处，分析 add_paths_to_joinrel： /* * add_paths_to_joinrel * Given a join relation and two component rels from which it can be made, * consider all possible paths that use the two component...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之九

调用关系：PortalRun -> PortalRunSelect -> ExecutorRun ExecutorRun，实际上会去运行 standard_ExecutorRun ->ExecutePlan： /* ---------------------------------------------------------------- * Execu...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之二十八

simple_exec_query函数中，有如下一句： plantree_list = pg_plan_queries(querytree_list, 0, NULL); 那么，plantree_list 里面，到底有什么，让我来给它大卸八块： plantree_list 是List *类型(指向List 的指针)： typedef struct List { NodeTag ...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之三十

接前面，继续分析： PortalStrategy ChoosePortalStrategy(List *stmts) { int nSetTag; ListCell *lc; /* * PORTAL_ONE_SELECT and PORTAL_UTIL_SELECT need only consider the * si...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之三十七

看： TupleTableSlot * ExecProcNode(PlanState *node) { TupleTableSlot *result; CHECK_FOR_INTERRUPTS(); if (node->chgParam != NULL) /* something changed */ ExecReScan(node); ...

文章 2017-12-20 来自：开发者社区

PostgreSQL在何处处理 sql查询之四十五

现在，将要进入最为重要的部分：分析如何制作执行计划的。先把它简化，看看NodeTag 在 PortalStart 之前，是如何得到的。先找到第一个相关程序：每一种执行计划（结点单位），都有一个对应的path。 /***************************************************************************** * ...

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