PostgreSQL源码学习执行器#10，11

  • Z时代
  • 2024-01-10
  • 分类：综合

database

本节介绍standard_ExecutorRun和ExecutorRun函数。

standard_ExecutorRun函数

//src/include/execurot/executor.h
extern void standard_ExecutorRun(QueryDesc *queryDesc,
			 ScanDirection direction, uint64 count, bool execute_once);

//src/backend/executor/execMain.c
Assert(queryDesc != NULL);
estate = queryDesc->estate;
Assert(estate != NULL);
Assert(!(estate->es_top_eflags & EXEC_FLAG_EXPLAIN_ONLY));
/* 切换为每个查询对应的内存上下文 */
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
/* 视情况开始执行器运行时间统计 */
if (queryDesc->totaltime)
	InstrStartNode(queryDesc->totaltime);
operation = queryDesc->operation;
dest = queryDesc->dest;
/* 若要发送元组，启动元组接收器 */
estate->es_processed = 0;
sendTuples = (operation == CMD_SELECT ||
		  queryDesc->plannedstmt->hasReturning);
if (sendTuples)
	dest->rStartup(dest, operation, queryDesc->tupDesc);
/* 执行plan */
if (!ScanDirectionIsNoMovement(direction))
{
	if (execute_once && queryDesc->already_executed)
		elog(ERROR, "can"t re-execute query flagged for single execution");
	queryDesc->already_executed = true;
	ExecutePlan(estate,
		queryDesc->planstate,
		queryDesc->plannedstmt->parallelModeNeeded,
		operation,
		sendTuples,
		count,
		direction,
		dest,
		execute_once);
}
/* 关闭元组接收器 */
if (sendTuples)
	dest->rShutdown(dest);
/* 结束执行器计时 */
if (queryDesc->totaltime)
	InstrStopNode(queryDesc->totaltime, estate->es_processed);
/* 切回内存上下文 */
MemoryContextSwitchTo(oldcontext);

ExecutorRun函数

void
ExecutorRun(QueryDesc *queryDesc,
			ScanDirection direction, uint64 count,
			bool execute_once)
{
	if (ExecutorRun_hook)
		(*ExecutorRun_hook) (queryDesc, direction, count, execute_once);
	else
		standard_ExecutorRun(queryDesc, direction, count, execute_once);
}

以上是 PostgreSQL源码学习执行器#10，11 的全部内容， 来源链接： utcz.com/z/534156.html

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