Patch from Andreas: when CREATE TABLE is followed by CREATE INDEX

before any tuples are loaded, preserve the default '1000 tuples' table
size estimate.

diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 89e45fb2bfc86add13b0c9a2d4f1bb3e9e903b41..1898f8f30878c8b0d043355129f5ad35b966a48a 100644 (file)
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.85 1999/05/25 16:08:03 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.86 1999/05/26 22:57:39 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -674,11 +674,10 @@ AddNewRelationTuple(Relation pg_class_desc,
     * enough to discourage the optimizer from using nested-loop plans.
     * With this hack, nested-loop plans will be preferred only after
     * the table has been proven to be small by VACUUM or CREATE INDEX.
-    * (NOTE: if user does CREATE TABLE, then CREATE INDEX, then loads
-    * the table, he still loses until he vacuums, because CREATE INDEX
-    * will set reltuples to zero.  Can't win 'em all.  Maintaining the
-    * stats on-the-fly would solve the problem, but the overhead of that
-    * would likely cost more than it'd save.)
+    * Maintaining the stats on-the-fly would solve the problem more cleanly,
+    * but the overhead of that would likely cost more than it'd save.
+    * (NOTE: CREATE INDEX inserts the same bogus estimates if it finds the
+    * relation has 0 rows and pages. See index.c.)
     * ----------------
     */
    new_rel_reltup->relpages = 10;      /* bogus estimates */

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 93f34ce0749d25bebcf2b951b930c25dde97d78d..0c8e9d77b789d299642dc81cee46a084f40b3653 100644 (file)
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.75 1999/05/25 16:08:06 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.76 1999/05/26 22:57:39 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1291,7 +1291,6 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
    if (!RelationIsValid(pg_class))
        elog(ERROR, "UpdateStats: could not open RELATION relation");
 
-
    if (!IsBootstrapProcessingMode())
    {
        tuple = SearchSysCacheTupleCopy(RELOID,
@@ -1320,34 +1319,48 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
    }
 
    /* ----------------
-    *  update statistics
+    * Figure values to insert.
+    *
+    * If we found zero tuples in the scan, do NOT believe it; instead put
+    * a bogus estimate into the statistics fields.  Otherwise, the common
+    * pattern "CREATE TABLE; CREATE INDEX; insert data" leaves the table
+    * with zero size statistics until a VACUUM is done.  The optimizer will
+    * generate very bad plans if the stats claim the table is empty when
+    * it is actually sizable.  See also CREATE TABLE in heap.c.
     * ----------------
     */
    relpages = RelationGetNumberOfBlocks(whichRel);
 
+   if (reltuples == 0)
+   {
+       if (relpages == 0)
+       {
+           /* Bogus defaults for a virgin table, same as heap.c */
+           reltuples = 1000;
+           relpages = 10;
+       }
+       else if (whichRel->rd_rel->relkind == RELKIND_INDEX && relpages <= 2)
+       {
+           /* Empty index, leave bogus defaults in place */
+           reltuples = 1000;
+       }
+       else
+           reltuples = relpages * NTUPLES_PER_PAGE(whichRel->rd_rel->relnatts);
+   }
+
    /*
     * We shouldn't have to do this, but we do...  Modify the reldesc in
     * place with the new values so that the cache contains the latest
     * copy.
     */
-
    whichRel->rd_rel->relhasindex = hasindex;
    whichRel->rd_rel->relpages = relpages;
    whichRel->rd_rel->reltuples = reltuples;
 
-   for (i = 0; i < Natts_pg_class; i++)
-   {
-       nulls[i] = heap_attisnull(tuple, i + 1) ? 'n' : ' ';
-       replace[i] = ' ';
-       values[i] = (Datum) NULL;
-   }
-
-   /*
-    * If reltuples wasn't supplied take an educated guess.
+   /* ----------------
+    *  Update statistics in pg_class.
+    * ----------------
     */
-   if (reltuples == 0)
-       reltuples = relpages * NTUPLES_PER_PAGE(whichRel->rd_rel->relnatts);
-
    if (IsBootstrapProcessingMode())
    {
 
@@ -1363,7 +1376,15 @@ UpdateStats(Oid relid, long reltuples, bool hasindex)
    }
    else
    {
-       /* during normal processing, work harder */
+       /* During normal processing, must work harder. */
+
+       for (i = 0; i < Natts_pg_class; i++)
+       {
+           nulls[i] = heap_attisnull(tuple, i + 1) ? 'n' : ' ';
+           replace[i] = ' ';
+           values[i] = (Datum) NULL;
+       }
+
        replace[Anum_pg_class_relpages - 1] = 'r';
        values[Anum_pg_class_relpages - 1] = (Datum) relpages;
        replace[Anum_pg_class_reltuples - 1] = 'r';
@@ -1438,12 +1459,10 @@ DefaultBuild(Relation heapRelation,
    char       *nullv;
    long        reltuples,
                indtuples;
-
 #ifndef OMIT_PARTIAL_INDEX
    ExprContext *econtext;
    TupleTable  tupleTable;
    TupleTableSlot *slot;
-
 #endif
    Node       *predicate;
    Node       *oldPred;
@@ -1524,13 +1543,13 @@ DefaultBuild(Relation heapRelation,
    {
        reltuples++;
 
+#ifndef OMIT_PARTIAL_INDEX
        /*
         * If oldPred != NULL, this is an EXTEND INDEX command, so skip
         * this tuple if it was already in the existing partial index
         */
        if (oldPred != NULL)
        {
-#ifndef OMIT_PARTIAL_INDEX
            /* SetSlotContents(slot, heapTuple); */
            slot->val = heapTuple;
            if (ExecQual((List *) oldPred, econtext) == true)
@@ -1538,7 +1557,6 @@ DefaultBuild(Relation heapRelation,
                indtuples++;
                continue;
            }
-#endif  /* OMIT_PARTIAL_INDEX */
        }
 
        /*
@@ -1547,13 +1565,12 @@ DefaultBuild(Relation heapRelation,
         */
        if (predicate != NULL)
        {
-#ifndef OMIT_PARTIAL_INDEX
            /* SetSlotContents(slot, heapTuple); */
            slot->val = heapTuple;
            if (ExecQual((List *) predicate, econtext) == false)
                continue;
-#endif  /* OMIT_PARTIAL_INDEX */
        }
+#endif  /* OMIT_PARTIAL_INDEX */
 
        indtuples++;
 
@@ -1586,12 +1603,12 @@ DefaultBuild(Relation heapRelation,
 
    heap_endscan(scan);
 
+#ifndef OMIT_PARTIAL_INDEX
    if (predicate != NULL || oldPred != NULL)
    {
-#ifndef OMIT_PARTIAL_INDEX
        ExecDestroyTupleTable(tupleTable, false);
-#endif  /* OMIT_PARTIAL_INDEX */
    }
+#endif  /* OMIT_PARTIAL_INDEX */
 
    pfree(nullv);
    pfree(datum);