From fc9e63049740042f9a8473f3caf22caeb9c08aed Mon Sep 17 00:00:00 2001
From: Diego Fronza <diego.fronza@percona.com>
Date: Wed, 6 Oct 2021 14:44:57 -0300
Subject: [PATCH] PG-254: Postpone variable initialization.

There were many variables being initialized in pgss_store() before
checking if the module was actually active, this would waste cpu
processor if the module is disabled.

To fix that, declare variables and initialize them only after check
that pg_stat_monitor is active.
---
 pg_stat_monitor.c | 46 ++++++++++++++++++++++++++--------------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/pg_stat_monitor.c b/pg_stat_monitor.c
index d6b6ddc..f739ff3 100644
--- a/pg_stat_monitor.c
+++ b/pg_stat_monitor.c
@@ -1486,37 +1486,44 @@ pgss_store(uint64 queryid,
 			JumbleState *jstate,
 			pgssStoreKind kind)
 {
-	pgssEntry		*entry;
+	pgssEntry       *entry;
 	pgssSharedState *pgss = pgsm_get_ss();
-	char			application_name[APPLICATIONNAME_LEN];
-	int    			application_name_len = pg_get_application_name(application_name);
-	bool 			reset = false;
-	uint64 			bucketid;
-	uint64 			prev_bucket_id;
+	char            application_name[APPLICATIONNAME_LEN];
+	int             application_name_len;
+	bool            reset = false;
+	uint64          bucketid;
+	uint64          prev_bucket_id;
     uint64          userid;
     int             con;
-	uint64 			dbid = MyDatabaseId;
-	uint64 			ip = pg_get_client_addr();
-	uint64			planid = plan_info ? plan_info->planid: 0;
-	uint64			appid = djb2_hash((unsigned char *)application_name, application_name_len);
+	uint64          dbid;
+	uint64          ip;
+	uint64          planid;
+	uint64          appid;
 	char            comments[512] = "";
-	bool		out_of_memory = false;
+	bool            out_of_memory = false;
+
 	/*  Monitoring is disabled */
 	if (!PGSM_ENABLED)
 		return;
 
-	Assert(query != NULL);
-	if (kind == PGSS_ERROR)
-        GetUserIdAndSecContext((unsigned int *)&userid, &con);
-    else
-     userid =  GetUserId();
-
-    extract_query_comments(query, comments, sizeof(comments));
-
 	/* Safety check... */
 	if (!IsSystemInitialized() || !pgss_qbuf[pg_atomic_read_u64(&pgss->current_wbucket)])
 		return;
 
+	Assert(query != NULL);
+	if (kind == PGSS_ERROR)
+		GetUserIdAndSecContext((unsigned int *)&userid, &con);
+	else
+		userid =  GetUserId();
+
+	dbid = MyDatabaseId;
+	application_name_len = pg_get_application_name(application_name);
+	ip = pg_get_client_addr();
+	planid = plan_info ? plan_info->planid: 0;
+	appid = djb2_hash((unsigned char *)application_name, application_name_len);
+
+	extract_query_comments(query, comments, sizeof(comments));
+
 	prev_bucket_id = pg_atomic_read_u64(&pgss->current_wbucket);
 	bucketid = get_next_wbucket(pgss);
 
@@ -1717,7 +1724,6 @@ pg_stat_monitor_internal(FunctionCallInfo fcinfo,
 		if (query_entry == NULL)
 			continue;
 
-
 		if (read_query(buf, bucketid, queryid, query_txt) == 0)
 		{
 			int len;