PostgreSQL源码学习调度器#12

  • Z时代
  • 2024-01-10
  • 分类：综合

database

本节介绍ProcessQuery函数。

相关数据结构

//src/include/executor/execdesc.h
typedef struct QueryDesc
{
	/* These fields are provided by CreateQueryDesc */
	CmdType		operation;		/* CMD_SELECT, CMD_UPDATE, etc. */
	PlannedStmt *plannedstmt;	/* planner"s output (could be utility, too) */
	const char *sourceText;		/* source text of the query */
	Snapshot	snapshot;		/* snapshot to use for query */
	Snapshot	crosscheck_snapshot;	/* crosscheck for RI update/delete */
	DestReceiver *dest;			/* the destination for tuple output */
	ParamListInfo params;		/* param values being passed in */
	QueryEnvironment *queryEnv; /* query environment passed in */
	int			instrument_options; /* OR of InstrumentOption flags */
	/* These fields are set by ExecutorStart */
	TupleDesc	tupDesc;		/* descriptor for result tuples */
	EState	   *estate;			/* executor"s query-wide state */
	PlanState  *planstate;		/* tree of per-plan-node state */
	/* This field is set by ExecutorRun */
	bool		already_executed;	/* true if previously executed */
	/* This is always set NULL by the core system, but plugins can change it */
	struct Instrumentation *totaltime;	/* total time spent in ExecutorRun */
} QueryDesc;

ProcessQuery函数

static void
ProcessQuery(PlannedStmt *plan,
			 const char *sourceText,
			 ParamListInfo params,
			 QueryEnvironment *queryEnv,
			 DestReceiver *dest,
			 char *completionTag);

//src/backend/tcop/pquery.c
/* 创建queryDesc */
queryDesc = CreateQueryDesc(plan, sourceText,
				GetActiveSnapshot(), InvalidSnapshot,
				dest, params, queryEnv, 0);
/* 做一些准备工作 */
ExecutorStart(queryDesc, 0);
/* 完成plan */
ExecutorRun(queryDesc, ForwardScanDirection, 0L, true);
/* 有需要的话，构建命令完成状态的字符串 */
if (completionTag)
{
	switch (queryDesc->operation)
	{
		case CMD_SELECT:
			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
					 "SELECT " UINT64_FORMAT,
					 queryDesc->estate->es_processed);
			break;
		case CMD_INSERT:
			/* lastoid doesn"t exist anymore */
			lastOid = InvalidOid;
			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
					 "INSERT %u " UINT64_FORMAT,
					 lastOid, queryDesc->estate->es_processed);
			break;
		case CMD_UPDATE:
			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
					 "UPDATE " UINT64_FORMAT,
					 queryDesc->estate->es_processed);
			break;
		case CMD_DELETE:
			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
					 "DELETE " UINT64_FORMAT,
					 queryDesc->estate->es_processed);
			break;
		default:
			strcpy(completionTag, "???");
			break;
	}
}
/* 做一些收尾工作，然后结束，释放资源 */
ExecutorFinish(queryDesc);
ExecutorEnd(queryDesc);
FreeQueryDesc(queryDesc);

以上是 PostgreSQL源码学习调度器#12 的全部内容， 来源链接： utcz.com/z/534190.html

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