Index: openacs-4/packages/acs-tcl/tcl/00-database-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/00-database-procs.tcl,v
diff -u -N -r1.69 -r1.70
--- openacs-4/packages/acs-tcl/tcl/00-database-procs.tcl	16 Jul 2007 00:54:16 -0000	1.69
+++ openacs-4/packages/acs-tcl/tcl/00-database-procs.tcl	17 Sep 2007 09:43:55 -0000	1.70
@@ -360,23 +360,56 @@
     switch $driverkey {
 
         postgresql {
-            # the following query will return a nextval if the sequnce
-            # is of relkind = 'S' (a sequnce).  if it is not of relkind = 'S'
-            # we will try querying it as a view:
+#             # the following query will return a nextval if the sequnce
+#             # is of relkind = 'S' (a sequnce).  if it is not of relkind = 'S'
+#             # we will try querying it as a view:
 
-            if { [db_0or1row -dbn $dbn nextval_sequence "
-                select nextval('${sequence}') as nextval
-                where (select relkind 
-                       from pg_class 
-                       where relname = '${sequence}') = 'S'
-            "]} {
-                return $nextval
-            } else {
-                ns_log debug "db_nextval: sequence($sequence) is not a real sequence.  perhaps it uses the view hack."
-                db_0or1row -dbn $dbn nextval_view "select nextval from ${sequence}"
-                return $nextval
+#             if { [db_0or1row -dbn $dbn nextval_sequence "
+#                 select nextval('${sequence}') as nextval
+#                 where (select relkind 
+#                        from pg_class 
+#                        where relname = '${sequence}') = 'S'
+#             "]} {
+#                 return $nextval
+#             } else {
+#                 ns_log debug "db_nextval: sequence($sequence) is not a real sequence.  perhaps it uses the view hack."
+#                 db_0or1row -dbn $dbn nextval_view "select nextval from ${sequence}"
+#                 return $nextval
+#             }
+          #
+          # The code above is just for documentation, how it worked
+          # before the change below. We keep now a per-thread table of
+          # the "known" sequences to avoid at runtime the query,
+          # whether the specified sequence is a real sequence or a
+          # view. This change makes this function more than a factor
+          # of 2 faster than before. 
+          #
+          # Disadvantage: If a new sequence is created, it is not immediately
+          # picked up (restart the server, or terminate thread).
+          #
+          # The best solution would certainly be to fix all views on sequences
+          # and to call db_nextval only with real sequence names.
+          #
+          # - gustaf neumann (17.9.2007)
+          #
+          if {![info exists ::db::sequences]} {
+            ns_log notice "-- creating per thread sequence table"
+            namespace eval ::db {}
+            foreach s [db_list -dbn $dbn relnames "select relname, relkind  from pg_class where relkind = 'S'"] {
+              set ::db::sequences($s) 1
             }
-
+          }
+          if {[info exists ::db::sequences(t_$sequence)]} {
+            #ns_log notice "-- found t_$sequence"
+            set nextval [db_string -dbn $dbn "nextval" "select nextval('t_$sequence')"]
+          } elseif {[info exists ::db::sequences($sequence)]} {
+            #ns_log notice "-- found $sequence"
+            set nextval [db_string -dbn $dbn "nextval" "select nextval('$sequence')"]
+          } else {
+            #ns_log notice "-- use view"
+            set nextval [db_string -dbn $dbn "nextval" "select nextval from $sequence"]
+          }
+          return $nextval
         }
 
         oracle -