From fb819a5b23a6441df420fcc74c1d5885ac3003c3 Mon Sep 17 00:00:00 2001
From: Ibrar Ahmed <ibrar.ahmad@gmail.com>
Date: Tue, 2 Feb 2021 17:52:41 +0000
Subject: [PATCH] PG-173: Added new WAL usage statistics.

---
 docs/USER_GUIDE.md | 15 +++++++++++++++
 pg_stat_monitor.c  | 38 +++++++++++++++++++++++++-------------
 2 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/docs/USER_GUIDE.md b/docs/USER_GUIDE.md
index 3245805..855ca5b 100644
--- a/docs/USER_GUIDE.md
+++ b/docs/USER_GUIDE.md
@@ -283,6 +283,21 @@ SELECT resp_calls, query FROM pg_stat_monitor;
 {1," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"} | select client_ip, query from pg_stat_monitor
 {3," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 1"} | select * from pg_stat_monitor_reset()
 {3," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 1"} | SELECT * FROM foo
+
+SELECT * FROM histogram(4, '4B64EE85C83D9AAC') AS a(range TEXT, freq INT, bar TEXT);
+   range   | freq |              bar
+-----------+------+--------------------------------
+ (0 - 1)}  |  692 | ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
+ (1 - 1)}  |    0 |
+ (1 - 1)}  |    0 |
+ (1 - 2)}  |  572 | ■■■■■■■■■■■■■■■■■■■■■■■■■
+ (2 - 3)}  |   74 | ■■■
+ (3 - 3)}  |    0 |
+ (3 - 5)}  |    9 |
+ (5 - 6)}  |    1 |
+ (6 - 7)}  |    1 |
+ (7 - 10)} |    1 |
+(10 rows)
 ```
 
 There are 10 timebase buckets of the time **`pg_stat_monitor.pgsm_respose_time_step`** in the field ``resp_calls``. The value in the field shows how many queries run in that period of time.
diff --git a/pg_stat_monitor.c b/pg_stat_monitor.c
index de47020..0e2e2ce 100644
--- a/pg_stat_monitor.c
+++ b/pg_stat_monitor.c
@@ -555,14 +555,16 @@ static void pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
 		exec_nested_level++;
 #endif
 
-		bufusage_start = pgBufferUsage;
-		INSTR_TIME_SET_CURRENT(start);
-
-		PG_TRY();
-		{
-			if (prev_ProcessUtility)
-				prev_ProcessUtility(pstmt, queryString,
-									context, params, queryEnv,
+	bufusage_start = pgBufferUsage;
+#if PG_VERSION_NUM >= 130000
+	walusage_start = pgWalUsage;
+#endif
+	INSTR_TIME_SET_CURRENT(start);
+	PG_TRY();
+	{
+		if (prev_ProcessUtility)
+			prev_ProcessUtility(pstmt, queryString,
+								context, params, queryEnv,
 									dest
 #if PG_VERSION_NUM >= 130000
 									,qc
@@ -804,6 +806,7 @@ static void pgss_store(uint64 queryId,
 	/* Safety check... */
 	if (!IsSystemInitialized() || !pgss_qbuf[pgss->current_wbucket])
 		return;
+	
 
 	/*
 	 * Confine our attention to the relevant part of the string, if the query
@@ -1001,9 +1004,18 @@ static void pgss_store(uint64 queryId,
 		if (sqlcode[0] != 0)
 			memset(&entry->counters.blocks, 0, sizeof(entry->counters.blocks));
 #if PG_VERSION_NUM >= 130000
-		e->counters.walusage.wal_records += walusage->wal_records;
-		e->counters.walusage.wal_fpi += walusage->wal_fpi;
-		e->counters.walusage.wal_bytes += walusage->wal_bytes;
+		if (sqlcode[0] == 0)
+		{
+			e->counters.walusage.wal_records += walusage->wal_records;
+			e->counters.walusage.wal_fpi += walusage->wal_fpi;
+			e->counters.walusage.wal_bytes += walusage->wal_bytes;
+		}
+		else
+		{
+			e->counters.walusage.wal_records = 0;
+			e->counters.walusage.wal_fpi = 0;
+			e->counters.walusage.wal_bytes  = 0;
+		}
 #endif
 		SpinLockRelease(&e->mutex);
 		}
@@ -2707,8 +2719,8 @@ get_histogram_bucket(double q_time)
 
 	for(index = 1; index <= b_count; index++)
 	{
-		double b_start = (index == 1)? 0 : exp(bucket_size * (index - 1));
-		double b_end = exp(bucket_size * index);
+		int64 b_start = (index == 1)? 0 : exp(bucket_size * (index - 1));
+		int64 b_end = exp(bucket_size * index);
 		if( (index == 1 && q_time < b_start)
 			|| (q_time >= b_start && q_time <= b_end)
 			|| (index == b_count && q_time > b_end) )