Blocked by

[Magnus Hagander <magnus(at)hagander(dot)net>]

Hi!

Attached patch implements a column in the server status view that shows if
a transaction is blocked, and what process it's blocked by. 

Since we're very close to RC, I'm sending it past here before doing
anything more. What do ppl think, are we ok with something like this for
this version or should I sit on it until the next one?

/Magnus

Index: frm/frmStatus.cpp
===================================================================
--- frm/frmStatus.cpp	(revision 6586)
+++ frm/frmStatus.cpp	(working copy)
@@ -120,6 +120,7 @@
     if (connection->BackendMinimumVersion(8, 3))
         statusList->AddColumn(_("TX start"), 50);
 
+	statusList->AddColumn(_("Blocked by"), 35);
     statusList->AddColumn(_("Query"), 500);
 
     lockList->AddColumn(wxT("PID"), 50);
@@ -326,7 +327,7 @@
     {
         // Status
 		long row=0;
-		pgSet *dataSet1=connection->ExecuteSet(wxT("SELECT * FROM pg_stat_activity ORDER BY procpid"));
+		pgSet *dataSet1=connection->ExecuteSet(wxT("SELECT *,(SELECT min(pid) FROM pg_locks l1 WHERE GRANTED AND relation IN (SELECT relation FROM pg_locks l2 WHERE l2.pid=procpid AND NOT granted)) AS blockedby FROM pg_stat_activity ORDER BY procpid"));
 		if (dataSet1)
 		{
             statusList->Freeze();
@@ -378,6 +379,7 @@
                     if (connection->BackendMinimumVersion(8, 3))
 					    statusList->SetItem(row, colpos++, dataSet1->GetVal(wxT("txn_start")));
 
+					statusList->SetItem(row, colpos++, dataSet1->GetVal(wxT("blockedby")));
     				statusList->SetItem(row, colpos, qry.Left(250));
 					row++;
 				}