Fix tuple counting in SP-GiST index build.

Count the number of tuples in the index honestly, instead of assuming
that it's the same as the number of tuples in the heap.  (It might be
different if the index is partial.)

Back-patch to all supported versions.

Tomas Vondra

Discussion: https://postgr.es/m/3b3d8eac-c709-0d25-088e-b98339a1b28a@2ndquadrant.com

diff --git a/src/backend/access/spgist/spginsert.c b/src/backend/access/spgist/spginsert.c
index ea54ec5bec40d65451da0acbb7efa167bb422d35..959c0b4517e5d6a33ab0e8f9e161bdc516e874fb 100644 (file)
--- a/src/backend/access/spgist/spginsert.c
+++ b/src/backend/access/spgist/spginsert.c
@@ -31,6 +31,7 @@
 typedef struct
 {
    SpGistState spgstate;       /* SPGiST's working state */
+   int64       indtuples;      /* total number of tuples indexed */
    MemoryContext tmpCtx;       /* per-tuple temporary context */
 } SpGistBuildState;
 
@@ -58,6 +59,9 @@ spgistBuildCallback(Relation index, HeapTuple htup, Datum *values,
        MemoryContextReset(buildstate->tmpCtx);
    }
 
+   /* Update total tuple count */
+   buildstate->indtuples += 1;
+
    MemoryContextSwitchTo(oldCtx);
    MemoryContextReset(buildstate->tmpCtx);
 }
@@ -134,6 +138,7 @@ spgbuild(PG_FUNCTION_ARGS)
     */
    initSpGistState(&buildstate.spgstate, index);
    buildstate.spgstate.isBuild = true;
+   buildstate.indtuples = 0;
 
    buildstate.tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
                                           "SP-GiST build temporary context",
@@ -149,7 +154,8 @@ spgbuild(PG_FUNCTION_ARGS)
    SpGistUpdateMetaPage(index);
 
    result = (IndexBuildResult *) palloc0(sizeof(IndexBuildResult));
-   result->heap_tuples = result->index_tuples = reltuples;
+   result->heap_tuples = reltuples;
+   result->index_tuples = buildstate.indtuples;
 
    PG_RETURN_POINTER(result);
 }