add plantuner.fix_empty_table GUC variable

diff --git a/README.plantuner b/README.plantuner
index 2d01f8e..49141c0 100644 (file)
--- a/README.plantuner
+++ b/README.plantuner
@@ -23,6 +23,12 @@ Motivation
    specific index(es), without dropping them, or to instruct planner to
    use specific index.
 
+   Next, for some workload PostgreSQL could be too pessimistic for
+   newly created tables and assumps much more rows in table than
+   it actually has. If plantuner.fix_empty_table GUC variable is set
+   to true then module will set to zero number of pages/tuples of
+   table which hasn't blocks in file.
+
 Installation
 
      * Get latest source of plantuner from CVS Repository

diff --git a/plantuner.c b/plantuner.c
index 13ab9b9..96d679a 100644 (file)
--- a/plantuner.c
+++ b/plantuner.c
@@ -30,19 +30,23 @@
 #include <postgres.h>
 
 #include <fmgr.h>
+#include <access/heapam.h>
 #include <catalog/namespace.h>
 #include <catalog/pg_class.h>
 #include <nodes/pg_list.h>
 #include <optimizer/plancat.h>
+#include <storage/bufmgr.h>
 #include <utils/builtins.h>
 #include <utils/guc.h>
 #include <utils/lsyscache.h>
+#include <utils/rel.h>
 
 PG_MODULE_MAGIC;
 
 static int     nIndexesOut = 0;
 static Oid     *indexesOut = NULL;
 get_relation_info_hook_type    prevHook = NULL;
+static bool    fix_empty_table = false;
 
 static char *indexesOutStr = "";
 
@@ -160,6 +164,35 @@ indexFilter(PlannerInfo *root, Oid relationObjectId, bool inhparent, RelOptInfo
                }
        }
 
+       if (fix_empty_table && rel)
+       {
+               
+
+       }
+
+}
+
+static void
+execPlantuner(PlannerInfo *root, Oid relationObjectId, bool inhparent, RelOptInfo *rel) {
+       Relation        relation;
+
+       relation = heap_open(relationObjectId, NoLock);
+       if (relation->rd_rel->relkind == RELKIND_RELATION)
+       {
+               if (fix_empty_table && RelationGetNumberOfBlocks(relation) == 0)
+               {
+                       /*
+                        * estimate_rel_size() could be too pessimistic for particular
+                        * workload
+                        */
+                       rel->pages = 0.0;
+                       rel->tuples = 0.0;
+               }
+
+               indexFilter(root, relationObjectId, inhparent, rel);
+       }
+       heap_close(relation, NoLock);
+
        /*
         * Call next hook if it exists 
         */
@@ -217,9 +250,28 @@ _PG_init(void)
                IndexFilterShow
        );
 
-       if (get_relation_info_hook != indexFilter )
+    DefineCustomBoolVariable(
+               "plantuner.fix_empty_table",
+               "Sets to zero estimations for empty tables",
+               "Sets to zero estimations for empty or newly created tables",
+               &fix_empty_table,
+#if PG_VERSION_NUM >= 80400
+               fix_empty_table,
+#endif
+               PGC_USERSET,
+#if PG_VERSION_NUM >= 80400
+               GUC_NOT_IN_SAMPLE,
+#if PG_VERSION_NUM >= 90100
+               NULL,
+#endif
+#endif
+               NULL,
+               NULL
+       );
+
+       if (get_relation_info_hook != execPlantuner )
        {
                prevHook = get_relation_info_hook;
-               get_relation_info_hook = indexFilter;
+               get_relation_info_hook = execPlantuner;
        }
 }