Actually there's a better way to do this, which is to count tuples

during the vacuumcleanup scan that we're going to do anyway.  Should
save a few cycles (one calculation per page, not per tuple) as well
as not having to depend on assumptions about heap and index being
in step.
I think this could probably be made to work for GIST too, but that
code looks messy enough that I'm disinclined to try right now.

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index e28faef141d83b966f3ba34d7dad669e7ffbdb16..dd6f1df6d2e871ca410e55417bcb513d4499a1ba 100644 (file)
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.139 2006/02/11 23:31:33 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.140 2006/02/12 00:18:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -539,16 +539,12 @@ btbulkdelete(PG_FUNCTION_ARGS)
    IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(1);
    void       *callback_state = (void *) PG_GETARG_POINTER(2);
    IndexBulkDeleteResult *result;
-   double      tuples_removed;
-   double      num_index_tuples;
+   double      tuples_removed = 0;
    OffsetNumber deletable[MaxOffsetNumber];
    int         ndeletable;
    Buffer      buf;
    BlockNumber num_pages;
 
-   tuples_removed = 0;
-   num_index_tuples = 0;
-
    /*
     * The outer loop iterates over index leaf pages, the inner over items on
     * a leaf page.  We issue just one _bt_delitems() call per page, so as to
@@ -566,19 +562,12 @@ btbulkdelete(PG_FUNCTION_ARGS)
     * could be stopped on those.
     *
     * We can skip the scan entirely if there's nothing to delete (indicated
-    * by callback_state == NULL) and the index isn't partial.  For a partial
-    * index we must scan in order to derive a trustworthy tuple count.
+    * by callback_state == NULL).
     */
-   if (callback_state || vac_is_partial_index(rel))
-   {
+   if (callback_state)
        buf = _bt_get_endpoint(rel, 0, false);
-   }
    else
-   {
-       /* skip scan and set flag for btvacuumcleanup */
        buf = InvalidBuffer;
-       num_index_tuples = -1;
-   }
 
    if (BufferIsValid(buf))     /* check for empty index */
    {
@@ -634,8 +623,6 @@ btbulkdelete(PG_FUNCTION_ARGS)
                        deletable[ndeletable++] = offnum;
                        tuples_removed += 1;
                    }
-                   else
-                       num_index_tuples += 1;
                }
            }
 
@@ -663,7 +650,7 @@ btbulkdelete(PG_FUNCTION_ARGS)
 
    result = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
    result->num_pages = num_pages;
-   result->num_index_tuples = num_index_tuples;
+   /* btvacuumcleanup will fill in num_index_tuples */
    result->tuples_removed = tuples_removed;
 
    PG_RETURN_POINTER(result);
@@ -687,6 +674,7 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
    BlockNumber *freePages;
    int         nFreePages,
                maxFreePages;
+   double      num_index_tuples = 0;
    BlockNumber pages_deleted = 0;
    MemoryContext mycontext;
    MemoryContext oldcontext;
@@ -801,6 +789,12 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
            MemoryContextSwitchTo(oldcontext);
            continue;           /* pagedel released buffer */
        }
+       else if (P_ISLEAF(opaque))
+       {
+           /* Count the index entries of live leaf pages */
+           num_index_tuples += PageGetMaxOffsetNumber(page) + 1 -
+               P_FIRSTDATAKEY(opaque);
+       }
        _bt_relbuf(rel, buf);
    }
 
@@ -847,16 +841,10 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
 
    /* update statistics */
    stats->num_pages = num_pages;
+   stats->num_index_tuples = num_index_tuples;
    stats->pages_deleted = pages_deleted;
    stats->pages_free = nFreePages;
 
-   /* if btbulkdelete skipped the scan, use heap's tuple count */
-   if (stats->num_index_tuples < 0)
-   {
-       Assert(info->num_heap_tuples >= 0);
-       stats->num_index_tuples = info->num_heap_tuples;
-   }
-
    PG_RETURN_POINTER(stats);
 }