Add lossy indicator to TBMIterateResult

TBMIterateResult->ntuples is -1 when the page in the bitmap is lossy.
Add an explicit lossy indicator so that we can move ntuples out of the
TBMIterateResult in a future commit.

Discussion: https://postgr.es/m/CA%2BhUKGLHbKP3jwJ6_%2BhnGi37Pw3BD5j2amjV3oSk7j-KyCnY7Q%40mail.gmail.com

diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c
index 63dd1f3679f0bae2dcd608d1cfd0f647d9b35814..54aecc1d1f1dbbaa4b8ad863d358c88ace64bcbc 100644 (file)
--- a/src/backend/access/gin/ginget.c
+++ b/src/backend/access/gin/ginget.c
@@ -827,7 +827,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
                         * in the bitmap.
                         */
                        while (entry->matchResult == NULL ||
-                                  (entry->matchResult->ntuples >= 0 &&
+                                  (!entry->matchResult->lossy &&
                                        entry->offset >= entry->matchResult->ntuples) ||
                                   entry->matchResult->blockno < advancePastBlk ||
                                   (ItemPointerIsLossyPage(&advancePast) &&
@@ -860,7 +860,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
                         * We're now on the first page after advancePast which has any
                         * items on it. If it's a lossy result, return that.
                         */
-                       if (entry->matchResult->ntuples < 0)
+                       if (entry->matchResult->lossy)
                        {
                                ItemPointerSetLossyPage(&entry->curItem,
                                                                                entry->matchResult->blockno);
@@ -879,6 +879,8 @@ entryGetItem(GinState *ginstate, GinScanEntry entry,
                         */
                        if (entry->matchResult->blockno == advancePastBlk)
                        {
+                               Assert(entry->matchResult->ntuples > 0);
+
                                /*
                                 * First, do a quick check against the last offset on the
                                 * page. If that's > advancePast, so are all the other

diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index c0bec0141540877ddf162a5f529ce0fe3d1479f8..269d581c2ec5013c9b525732e262202b1aa72776 100644 (file)
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2170,7 +2170,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
                VM_ALL_VISIBLE(scan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer))
        {
                /* can't be lossy in the skip_fetch case */
-               Assert(tbmres->ntuples >= 0);
+               Assert(!tbmres->lossy);
                Assert(bscan->rs_empty_tuples_pending >= 0);
 
                bscan->rs_empty_tuples_pending += tbmres->ntuples;
@@ -2207,7 +2207,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
        /*
         * We need two separate strategies for lossy and non-lossy cases.
         */
-       if (tbmres->ntuples >= 0)
+       if (!tbmres->lossy)
        {
                /*
                 * Bitmap is non-lossy, so we just look through the offsets listed in
@@ -2268,10 +2268,10 @@ heapam_scan_bitmap_next_block(TableScanDesc scan,
        Assert(ntup <= MaxHeapTuplesPerPage);
        hscan->rs_ntuples = ntup;
 
-       if (tbmres->ntuples >= 0)
-               (*exact_pages)++;
-       else
+       if (tbmres->lossy)
                (*lossy_pages)++;
+       else
+               (*exact_pages)++;
 
        /*
         * Return true to indicate that a valid block was found and the bitmap is

diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 66b3c387d530ef942a65b41117922972cca5cdb8..3e0bca651f56f3b72e51e1c0c091af77d5712b82 100644 (file)
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -961,12 +961,13 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
  *
  * Returns a TBMIterateResult representing one page, or NULL if there are
  * no more pages to scan.  Pages are guaranteed to be delivered in numerical
- * order.  If result->ntuples < 0, then the bitmap is "lossy" and failed to
+ * order.  If lossy is true, then the bitmap is "lossy" and failed to
  * remember the exact tuples to look at on this page --- the caller must
  * examine all tuples on the page and check if they meet the intended
- * condition.  If result->recheck is true, only the indicated tuples need
+ * condition.  result->ntuples is set to -1 when the bitmap is lossy.
+ * If result->recheck is true, only the indicated tuples need
  * be examined, but the condition must be rechecked anyway.  (For ease of
- * testing, recheck is always set true when ntuples < 0.)
+ * testing, recheck is always set true when lossy is true.)
  */
 TBMIterateResult *
 tbm_private_iterate(TBMPrivateIterator *iterator)
@@ -1012,6 +1013,7 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
                        /* Return a lossy page indicator from the chunk */
                        output->blockno = chunk_blockno;
                        output->ntuples = -1;
+                       output->lossy = true;
                        output->recheck = true;
                        iterator->schunkbit++;
                        return output;
@@ -1033,6 +1035,7 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
                ntuples = tbm_extract_page_tuple(page, output);
                output->blockno = page->blockno;
                output->ntuples = ntuples;
+               output->lossy = false;
                output->recheck = page->recheck;
                iterator->spageptr++;
                return output;
@@ -1105,6 +1108,7 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
                        /* Return a lossy page indicator from the chunk */
                        output->blockno = chunk_blockno;
                        output->ntuples = -1;
+                       output->lossy = true;
                        output->recheck = true;
                        istate->schunkbit++;
 
@@ -1122,6 +1126,7 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
                ntuples = tbm_extract_page_tuple(page, output);
                output->blockno = page->blockno;
                output->ntuples = ntuples;
+               output->lossy = false;
                output->recheck = page->recheck;
                istate->spageptr++;
 

diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index a6ffeac90be9a0469cc82ddef80b920051651a6f..8cd93d90a868ecb5e2717b7f28ba9d8b8828b06f 100644 (file)
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -54,9 +54,10 @@ typedef struct TBMIterator
 typedef struct TBMIterateResult
 {
        BlockNumber blockno;            /* page number containing tuples */
-       int                     ntuples;                /* -1 indicates lossy result */
+       int                     ntuples;                /* -1 when lossy */
+       bool            lossy;
        bool            recheck;                /* should the tuples be rechecked? */
-       /* Note: recheck is always true if ntuples < 0 */
+       /* Note: recheck is always true if lossy */
        OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
 } TBMIterateResult;