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 86d9e3c..35a4d08 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);
@@ -2255,6 +2257,39 @@ errdetail_abort(void)
 }
 
 /*
+ * 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
  *
  * Process a "Describe" message for a prepared statement
@@ -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()));
                }
 
                /*