Re: Request - repeat value of \pset title during \watch interations

["David G. Johnston" <david.g.johnston@xxxxxxxxx>]

Adding -hackers for consideration in the Commitfest.

Thanks!

David J.

>>>Original request by me

http://www.postgresql.org/message-id/CAKFQuwZqjz-je3Z=8JDOdYm3JM-N2UL4cuqy5VH8N75E5v1VVQ@xxxxxxxxxxxxxx

When executing a query using \watch in psql the first execution of the query includes "Title is [...]" when \pset title is in use.  Subsequent executions do not.  Once that first display goes off-screen the information in the title is no longer readily accessible.  If using \watch for a long-running monitoring query it can be helpful to incorporate some context information into the title.

---------- Forwarded message ----------
From: Michael Paquier <michael.paquier@xxxxxxxxx>
Date: Thu, Jan 28, 2016 at 6:01 AM
Subject: Re: Request - repeat value of \pset title during \watch interations
To: "David G. Johnston" <david.g.johnston@xxxxxxxxx>
Cc: Tom Lane <tgl@xxxxxxxxxxxxx>, "pgsql-general@xxxxxxxxxxxxxx" <pgsql-general@xxxxxxxxxxxxxx>


On Thu, Jan 28, 2016 at 1:54 PM, David G. Johnston
<david.g.johnston@xxxxxxxxx> wrote:
> On Wed, Jan 27, 2016 at 9:13 PM, Michael Paquier <michael.paquier@xxxxxxxxx>
> wrote:
>>
>> On Thu, Jan 28, 2016 at 9:34 AM, David G. Johnston
>> <david.g.johnston@xxxxxxxxx> wrote:
>> > So how about:
>> >
>> > + snprintf(title, strlen(myopt.title) + 50,
>> > + _("Watch every %lds\t%s\t%s"),
>> > +  sleep, head_title, asctime(localtime(&timer)));
>>
>> I would just keep the timestamp and the title separated so what do you
>> think about that instead?
>> Watch every Xs   $timestamp
>> $head_title
>
>
> That works.  I like having the title immediately above the table.
>
> The other option that came to mind would be to place the time information
> after the table display while leaving the title before it.  On an output
> that requires more vertical space than is available in the terminal one
> would no longer have to scroll up to confirm last execution time.  If doing
> this I'd probably get rid of any logic that attempts to center the time
> information on the table and simply leave it left-aligned.

​And the example:

​

OK, attached is an updated patch. How does that look?

                               Watch every 5s    Fri Jan 29 13:06:31 2016

This is a medium length title
                                                repeat                                               
------------------------------------------------------------------------------------------------------
 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

(1 row)

​

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 9750a5b..3241d27 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -3020,7 +3020,8 @@ static bool
 do_watch(PQExpBuffer query_buf, long sleep)
 {
 	printQueryOpt myopt = pset.popt;
-	char		title[50];
+	char		 *title;
+	bool		 *head_title = NULL;
 
 	if (!query_buf || query_buf->len <= 0)
 	{
@@ -3034,6 +3035,18 @@ do_watch(PQExpBuffer query_buf, long sleep)
 	 */
 	myopt.topt.pager = 0;
 
+	/*
+	 * Take into account any title present in the user setup as a part of
+	 * what is printed for each iteration by using it as a header.
+	 */
+	if (myopt.title)
+	{
+		title = pg_malloc(strlen(myopt.title) + 50);
+		head_title = pg_strdup(myopt.title);
+	}
+	else
+		title = pg_malloc(50);
+
 	for (;;)
 	{
 		int			res;
@@ -3045,8 +3058,13 @@ do_watch(PQExpBuffer query_buf, long sleep)
 		 * of completion of the command?
 		 */
 		timer = time(NULL);
-		snprintf(title, sizeof(title), _("Watch every %lds\t%s"),
-				 sleep, asctime(localtime(&timer)));
+		if (head_title)
+			snprintf(title, strlen(myopt.title) + 50,
+					 _("Watch every %lds\t%s\n%s"),
+					 sleep, asctime(localtime(&timer)), head_title);
+		else
+			snprintf(title, 50, _("Watch every %lds\t%s"),
+					 sleep, asctime(localtime(&timer)));
 		myopt.title = title;
 
 		/* Run the query and print out the results */
@@ -3059,7 +3077,11 @@ do_watch(PQExpBuffer query_buf, long sleep)
 		if (res == 0)
 			break;
 		if (res == -1)
+		{
+			pg_free(title);
+			pg_free(head_title);
 			return false;
+		}
 
 		/*
 		 * Set up cancellation of 'watch' via SIGINT.  We redo this each time
@@ -3084,6 +3106,8 @@ do_watch(PQExpBuffer query_buf, long sleep)
 		sigint_interrupt_enabled = false;
 	}
 
+	pg_free(title);
+	pg_free(head_title);
 	return true;
 }
 

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