本节介绍ProcessQuery函数。

相关数据结构

//src/include/executor/execdesc.h

typedef struct QueryDesc
{
	
	CmdType		operation;		
	PlannedStmt *plannedstmt;	
	const char *sourceText;		
	Snapshot	snapshot;		
	Snapshot	crosscheck_snapshot;	
	DestReceiver *dest;			
	ParamListInfo params;		
	QueryEnvironment *queryEnv; 
	int			instrument_options; 

	
	TupleDesc	tupDesc;		
	EState	   *estate;			
	PlanState  *planstate;		

	
	bool		already_executed;	

	
	struct Instrumentation *totaltime;	
} 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


queryDesc = CreateQueryDesc(plan, sourceText,
				GetActiveSnapshot(), InvalidSnapshot,
				dest, params, queryEnv, 0);


ExecutorStart(queryDesc, 0);


ExecutorRun(queryDesc, ForwardScanDirection, 0L, true);


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 = 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;
	}
}


ExecutorFinish(queryDesc);
ExecutorEnd(queryDesc);

FreeQueryDesc(queryDesc);