GUC assign hooks that look at external state in deciding whether a

setting is valid must ignore that state and permit the assignment anyway
when source is PGC_S_OVERRIDE.  Otherwise they may disallow a rollback
at transaction abort, which is The Wrong Thing.  Per example from
Michael Fuhr 12-Sep-04.

diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index e0ccd668e591a4e3ac3a1a3507179ec0b46ffc81..26816463b579bd5d7954b814301964d667662821 100644 (file)
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.103 2004/08/31 19:28:51 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.104 2004/09/24 19:42:58 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -481,7 +481,8 @@ assign_XactIsoLevel(const char *value, bool doit, GucSource source)
                        ereport(ERROR,
                                        (errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
                                         errmsg("SET TRANSACTION ISOLATION LEVEL must be called before any query")));
-               else
+               /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
+               else if (source != PGC_S_OVERRIDE)
                        return NULL;
        }
        if (IsSubTransaction())
@@ -490,7 +491,8 @@ assign_XactIsoLevel(const char *value, bool doit, GucSource source)
                        ereport(ERROR,
                                        (errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
                                         errmsg("SET TRANSACTION ISOLATION LEVEL must not be called in a subtransaction")));
-               else
+               /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
+               else if (source != PGC_S_OVERRIDE)
                        return NULL;
        }
 

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 436c57b750f4b192302c2ba01e5b0b9e1480c1bd..4fb2fad4a6b485a68b095b86db3190b1d512d928 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.238 2004/08/31 22:43:58 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.239 2004/09/24 19:43:03 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -5532,7 +5532,8 @@ assign_stage_log_stats(bool newval, bool doit, GucSource source)
                        ereport(ERROR,
                                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                         errmsg("cannot enable parameter when \"log_statement_stats\" is true")));
-               else
+               /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
+               else if (source != PGC_S_OVERRIDE)
                        return false;
        }
        return true;
@@ -5550,7 +5551,8 @@ assign_log_stats(bool newval, bool doit, GucSource source)
                                         errmsg("cannot enable \"log_statement_stats\" when "
                                                        "\"log_parser_stats\", \"log_planner_stats\", "
                                                        "or \"log_executor_stats\" is true")));
-               else
+               /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
+               else if (source != PGC_S_OVERRIDE)
                        return false;
        }
        return true;
@@ -5566,7 +5568,9 @@ assign_transaction_read_only(bool newval, bool doit, GucSource source)
                        ereport(ERROR,
                                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                         errmsg("cannot set transaction read-write mode inside a read-only transaction")));
-               return false;
+               /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
+               else if (source != PGC_S_OVERRIDE)
+                       return false;
        }
        return true;
 }