PG-286: Small performance improvements.

pgss_ExecutorEnd: Avoid unnecessary memset(plan_info, 0, ...).
We only use this object if the condition below is true, in which case we
already initialize all the fields in the object, also we now store the
plan string length (plan_info.plan_len) to avoid calling strlen on it
again later:
if (queryDesc->operation == CMD_SELECT && PGSM_QUERY_PLAN) {
... here we initialize plan_info

If the condition is false, then we pass a NULL PlanInfo* to the
pgss_store to avoid more unnecessary processing.

pgss_planner_hook: Similar, avoid memset(plan_info, 0, ...) this object
is not used here, so we pass NULL to pgss_store.

pg_get_application_name: Remove call to strlen, snprintf already give us
the calculated string length, so we just return it.

pg_get_client_addr: Cache localhost, avoid calling
ntohl(inet_addr("127.0.0.1")) all the time.

pgss_update_entry: Make use of PlanInfo->plan_len, avoiding a call to
strlen again.

intarray_get_datum: Init the string by setting the first byte to '\0'.

pg_stat_monitor.c

@@ -656,14 +656,15 @@ pgss_ExecutorEnd(QueryDesc *queryDesc)
 	uint64             queryId       = queryDesc->plannedstmt->queryId;
     SysInfo            sys_info;
 	PlanInfo           plan_info;
+	PlanInfo		   *plan_ptr = NULL;
 
-	/* Extract the plan information in case of SELECT statment */
+	/* Extract the plan information in case of SELECT statement */	
-	memset(&plan_info, 0, sizeof(PlanInfo));
 	if (queryDesc->operation == CMD_SELECT && PGSM_QUERY_PLAN)
 	{		
 		MemoryContext mct = MemoryContextSwitchTo(TopMemoryContext);
-		snprintf(plan_info.plan_text, PLAN_TEXT_LEN, "%s", pgss_explain(queryDesc));
+		plan_info.plan_len = snprintf(plan_info.plan_text, PLAN_TEXT_LEN, "%s", pgss_explain(queryDesc));
-		plan_info.planid = DatumGetUInt64(hash_any_extended((const unsigned char*)plan_info.plan_text, strlen(plan_info.plan_text), 0));
+		plan_info.planid = DatumGetUInt64(hash_any_extended((const unsigned char*)plan_info.plan_text, plan_info.plan_len, 0));
+		plan_ptr = &plan_info;
 		MemoryContextSwitchTo(mct);
 	}
 
@@ -682,7 +683,7 @@ pgss_ExecutorEnd(QueryDesc *queryDesc)
 
 		pgss_store(queryId,                                 /* query id */
 					queryDesc->sourceText,					/* query text */
-					&plan_info,								/* PlanInfo */
+					plan_ptr,								/* PlanInfo */
 					queryDesc->operation,					/* CmdType */
 					&sys_info,								/* SysInfo */
 					NULL,									/* ErrorInfo */
@@ -784,7 +785,6 @@ pgss_planner_hook(Query *parse, const char *query_string, int cursorOptions, Par
 
 	if (PGSM_TRACK_PLANNING && query_string && parse->queryId != UINT64CONST(0) && !IsParallelWorker())
 	{
-		PlanInfo	plan_info;
 		instr_time	start;
 		instr_time	duration;
 		BufferUsage bufusage_start;
@@ -792,7 +792,6 @@ pgss_planner_hook(Query *parse, const char *query_string, int cursorOptions, Par
 		WalUsage	walusage_start;
 		WalUsage    walusage;
 
-		memset(&plan_info, 0, sizeof(PlanInfo));
 		/* We need to track buffer usage as the planner can access them. */
 		bufusage_start = pgBufferUsage;
 
@@ -836,7 +835,7 @@ pgss_planner_hook(Query *parse, const char *query_string, int cursorOptions, Par
 		WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
 		pgss_store(parse->queryId,          		/* query id */
 				query_string,						/* query */
-				&plan_info,							/* PlanInfo */
+				NULL,								/* PlanInfo */
 				parse->commandType,					/* CmdType */
 				NULL,								/* SysInfo */
 				NULL,								/* ErrorInfo */
@@ -1142,41 +1141,41 @@ pg_get_application_name(char *application_name)
 	if (!beentry)
 		return snprintf(application_name, APPLICATIONNAME_LEN, "%s", "postmaster");
 
-	snprintf(application_name, APPLICATIONNAME_LEN, "%s", beentry->st_appname);
+	return snprintf(application_name, APPLICATIONNAME_LEN, "%s", beentry->st_appname);	
-	return strlen(application_name);
 }
 
-/*
- * Store some statistics for a statement.
- *
- * If queryId is 0 then this is a utility statement and we should compute
- * a suitable queryId internally.
- *
- * If jstate is not NULL then we're trying to create an entry for which
- * we have no statistics as yet; we just want to record the normalized
- */
-
 static uint
 pg_get_client_addr(void)
 {
 	PgBackendStatus *beentry = pg_get_backend_status();
 	char	remote_host[NI_MAXHOST];
 	int		ret;
+	static uint localhost = 0;
+
+	remote_host[0] = '\0';
 
 	if (!beentry)
 		return ntohl(inet_addr("127.0.0.1"));
 	
-	memset(remote_host, 0x0, NI_MAXHOST);
 	ret = pg_getnameinfo_all(&beentry->st_clientaddr.addr,
 							 beentry->st_clientaddr.salen,
 							 remote_host, sizeof(remote_host),
 							 NULL, 0,
 							 NI_NUMERICHOST | NI_NUMERICSERV);
 	if (ret != 0)
-		return ntohl(inet_addr("127.0.0.1"));
+	{
+		if (localhost == 0)
+			localhost = ntohl(inet_addr("127.0.0.1"));
+		return localhost;
+	}
 
 	if (strcmp(remote_host, "[local]") == 0)
-		return ntohl(inet_addr("127.0.0.1"));
+	{
+		if (localhost == 0)
+			localhost = ntohl(inet_addr("127.0.0.1"));
+		return localhost;
+	}
+
 	return ntohl(inet_addr(remote_host));
 }
 
@@ -1204,7 +1203,7 @@ pgss_update_entry(pgssEntry *entry,
 	int             	message_len = error_info ? strlen (error_info->message) : 0;
 	int             	comments_len = comments ? strlen (comments) : 0;
 	int             	sqlcode_len = error_info ? strlen (error_info->sqlcode) : 0;
-	int             	plan_text_len = plan_info ? strlen (plan_info->plan_text) : 0;
+	int             	plan_text_len = plan_info ? plan_info->plan_len : 0;
 
 
 	/* volatile block */
@@ -3018,18 +3017,16 @@ intarray_get_datum(int32 arr[], int len)
 	int     j;
 	char    str[1024];
 	char    tmp[10];
-	bool    first = true;
 
-	memset(str, 0, sizeof(str));
+	str[0] = '\0';
 
 	/* Need to calculate the actual size, and avoid unnessary memory usage */
 	for (j = 0; j < len; j++)
 	{
-		if (first)
+		if (!str[0])
 		{
 			snprintf(tmp, 10, "%d", arr[j]);
 			strcat(str,tmp);
-			first = false;
 			continue;
 		}
 		snprintf(tmp, 10, ",%d", arr[j]);

pg_stat_monitor.h

@@ -189,6 +189,7 @@ typedef struct PlanInfo
 {
 	uint64		planid;						/* plan identifier */
 	char 		plan_text[PLAN_TEXT_LEN];	/* plan text */
+	size_t		plan_len;                   /* strlen(plan_text) */
 } PlanInfo;
 
 typedef struct pgssHashKey