Improve readability of the output of psql's \timing command.

In addition to the existing decimal-milliseconds output value,
display the same value in mm:ss.fff format if it exceeds one second.
Tack on hours and even days fields if the interval is large enough.
This avoids needing mental arithmetic to convert the values into
customary time units.

Corey Huinker, reviewed by Gerdan Santos; bikeshedding by many

Discussion: <CADkLM=dbC4R8sbbuFXQVBFWoJGQkTEW8RWnC0PbW9nZsovZpJQ@mail.gmail.com>

doc/src/sgml/ref/psql-ref.sgml

@@ -2789,8 +2789,11 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
        <term><literal>\timing [ <replaceable class="parameter">on</replaceable> | <replaceable class="parameter">off</replaceable> ]</literal></term>
         <listitem>
         <para>
-         Without parameter, toggles a display of how long each SQL statement
-         takes, in milliseconds.  With parameter, sets same.
+         With a parameter, turns displaying of how long each SQL statement
+         takes on or off.  Without a parameter, toggles the display between
+         on and off.  The display is in milliseconds; intervals longer than
+         1 second are also shown in minutes:seconds format, with hours and
+         days fields added if needed.
         </para>
        </listitem>
       </varlistentry>

src/bin/psql/common.c

@@ -10,6 +10,7 @@
 
 #include <ctype.h>
 #include <limits.h>
+#include <math.h>
 #include <signal.h>
 #ifndef WIN32
 #include <unistd.h>				/* for write() */
@@ -531,6 +532,57 @@ ClearOrSaveResult(PGresult *result)
 }
 
 
+/*
+ * Print microtiming output.  Always print raw milliseconds; if the interval
+ * is >= 1 second, also break it down into days/hours/minutes/seconds.
+ */
+static void
+PrintTiming(double elapsed_msec)
+{
+	double		seconds;
+	double		minutes;
+	double		hours;
+	double		days;
+
+	if (elapsed_msec < 1000.0)
+	{
+		/* This is the traditional (pre-v10) output format */
+		printf(_("Time: %.3f ms\n"), elapsed_msec);
+		return;
+	}
+
+	/*
+	 * Note: we could print just seconds, in a format like %06.3f, when the
+	 * total is less than 1min.  But that's hard to interpret unless we tack
+	 * on "s" or otherwise annotate it.  Forcing the display to include
+	 * minutes seems like a better solution.
+	 */
+	seconds = elapsed_msec / 1000.0;
+	minutes = floor(seconds / 60.0);
+	seconds -= 60.0 * minutes;
+	if (minutes < 60.0)
+	{
+		printf(_("Time: %.3f ms (%02d:%06.3f)\n"),
+			   elapsed_msec, (int) minutes, seconds);
+		return;
+	}
+
+	hours = floor(minutes / 60.0);
+	minutes -= 60.0 * hours;
+	if (hours < 24.0)
+	{
+		printf(_("Time: %.3f ms (%02d:%02d:%06.3f)\n"),
+			   elapsed_msec, (int) hours, (int) minutes, seconds);
+		return;
+	}
+
+	days = floor(hours / 24.0);
+	hours -= 24.0 * days;
+	printf(_("Time: %.3f ms (%.0f d %02d:%02d:%06.3f)\n"),
+		   elapsed_msec, days, (int) hours, (int) minutes, seconds);
+}
+
+
 /*
  * PSQLexec
  *
@@ -679,7 +731,7 @@ PSQLexecWatch(const char *query, const printQueryOpt *opt)
 
 	/* Possible microtiming output */
 	if (pset.timing)
-		printf(_("Time: %.3f ms\n"), elapsed_msec);
+		PrintTiming(elapsed_msec);
 
 	return 1;
 }
@@ -1332,7 +1384,7 @@ SendQuery(const char *query)
 
 	/* Possible microtiming output */
 	if (pset.timing)
-		printf(_("Time: %.3f ms\n"), elapsed_msec);
+		PrintTiming(elapsed_msec);
 
 	/* check for events that may occur during query execution */