Add explanatory detail to Hot Standby cancelation error messages

with errdetail(). Add errhint() to suggest retry in certain cases.

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 86d9e3c9847741d91839bf66bc6cc8d60e46e9b4..35a4d087ce768c1f9dcf39575f5142b48b396ebf 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.586 2010/01/23 16:37:12 sriggs Exp $
+ *   $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.587 2010/01/23 17:04:05 sriggs Exp $
  *
  * NOTES
  *   this is the "main" module of the postgres backend and
@@ -172,8 +172,9 @@ static int  UseNewLine = 1;     /* Use newlines query delimiters (the default) */
 static int UseNewLine = 0;     /* Use EOF as query delimiters */
 #endif   /* TCOP_DONTUSENEWLINE */
 
-/* whether we were cancelled during recovery by conflict processing or not */
+/* whether or not, and why, we were cancelled by conflict with recovery */
 static bool RecoveryConflictPending = false;
+static ProcSignalReason    RecoveryConflictReason;
 
 /* ----------------------------------------------------------------
  *     decls for routines only used in this file
@@ -188,6 +189,7 @@ static bool check_log_statement(List *stmt_list);
 static int errdetail_execute(List *raw_parsetree_list);
 static int errdetail_params(ParamListInfo params);
 static int  errdetail_abort(void);
+static int  errdetail_recovery_conflict(void);
 static void start_xact_command(void);
 static void finish_xact_command(void);
 static bool IsTransactionExitStmt(Node *parsetree);
@@ -2254,6 +2256,39 @@ errdetail_abort(void)
    return 0;
 }
 
+/*
+ * errdetail_recovery_conflict
+ *
+ * Add an errdetail() line showing conflict source.
+ */
+static int
+errdetail_recovery_conflict(void)
+{
+   switch (RecoveryConflictReason)
+   {
+       case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:
+               errdetail("User was holding shared buffer pin for too long.");
+               break;
+       case PROCSIG_RECOVERY_CONFLICT_LOCK:
+               errdetail("User was holding a relation lock for too long.");
+               break;
+       case PROCSIG_RECOVERY_CONFLICT_TABLESPACE:
+               errdetail("User was or may have been using tablespace that must be dropped.");
+               break;
+       case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
+               errdetail("User query might have needed to see row versions that must be removed.");
+               break;
+       case PROCSIG_RECOVERY_CONFLICT_DATABASE:
+               errdetail("User was connected to a database that must be dropped.");
+               break;
+       default:
+               break;
+               /* no errdetail */
+   }
+
+   return 0;
+}
+
 /*
  * exec_describe_statement_message
  *
@@ -2716,6 +2751,7 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
    */
    if (!proc_exit_inprogress)
    {
+       RecoveryConflictReason = reason;
        switch (reason)
        {
            case PROCSIG_RECOVERY_CONFLICT_BUFFERPIN:
@@ -2835,7 +2871,8 @@ ProcessInterrupts(void)
        else if (RecoveryConflictPending)
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
-                    errmsg("terminating connection due to conflict with recovery")));
+                    errmsg("terminating connection due to conflict with recovery"),
+                    errdetail_recovery_conflict()));
        else
            ereport(FATAL,
                    (errcode(ERRCODE_ADMIN_SHUTDOWN),
@@ -2883,11 +2920,15 @@ ProcessInterrupts(void)
            if (DoingCommandRead)
                ereport(FATAL,
                        (errcode(ERRCODE_ADMIN_SHUTDOWN),
-                        errmsg("terminating connection due to conflict with recovery")));
+                        errmsg("terminating connection due to conflict with recovery"),
+                        errdetail_recovery_conflict(),
+                        errhint("In a moment you should be able to reconnect to the"
+                                " database and repeat your command.")));
            else
                ereport(ERROR,
                        (errcode(ERRCODE_QUERY_CANCELED),
-                        errmsg("canceling statement due to conflict with recovery")));
+                        errmsg("canceling statement due to conflict with recovery"),
+                        errdetail_recovery_conflict()));
        }
 
        /*