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 3ce07c4a37fea3332c4924eb1ace218179156a80..f8f7fa92fe58efe975f7a90ea822b59ac9f733cf 100644 (file)
--- a/src/backend/access/spgist/spginsert.c
+++ b/src/backend/access/spgist/spginsert.c
@@ -30,6 +30,7 @@
 typedef struct
 {
        SpGistState spgstate;           /* SPGiST's working state */
+       int64           indtuples;              /* total number of tuples indexed */
        MemoryContext tmpCtx;           /* per-tuple temporary context */
 } SpGistBuildState;
 
@@ -57,6 +58,9 @@ spgistBuildCallback(Relation index, HeapTuple htup, Datum *values,
                MemoryContextReset(buildstate->tmpCtx);
        }
 
+       /* Update total tuple count */
+       buildstate->indtuples += 1;
+
        MemoryContextSwitchTo(oldCtx);
        MemoryContextReset(buildstate->tmpCtx);
 }
@@ -130,6 +134,7 @@ spgbuild(PG_FUNCTION_ARGS)
         */
        initSpGistState(&buildstate.spgstate, index);
        buildstate.spgstate.isBuild = true;
+       buildstate.indtuples = 0;
 
        buildstate.tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
                                                                                   "SP-GiST build temporary context",
@@ -145,7 +150,8 @@ 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);
 }