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Fixed recall for HNSW after vacuuming

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This commit is contained in:
Andrew Kane
2023-08-13 15:37:47 -07:00
parent dc8d467ba5
commit 23cb79c1dc
2 changed files with 31 additions and 9 deletions
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35
src/hnswutils.c
View File

@@ -606,10 +606,6 @@ HnswSearchLayer(Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *pro
if (e->element->deleted)
continue;
/* Skip for inserts if deleting */
if (inserting && list_length(e->element->heaptids) == 0)
continue;
/* Skip self for vacuuming update */
if (skipElement != NULL && e->element->neighborPage == skipElement->neighborPage && e->element->neighborOffno == skipElement->neighborOffno)
continue;
@@ -628,6 +624,8 @@ HnswSearchLayer(Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *pro
pairingheap_add(C, &(CreatePairingHeapNode(ec)->ph_node));
pairingheap_add(W, &(CreatePairingHeapNode(ec)->ph_node));
/* TODO Possibly don't count elements being deleted in wlen */
wlen++;
/* No need to decrement wlen */
@@ -889,6 +887,26 @@ HnswUpdateConnection(HnswElement element, HnswCandidate * hc, int m, int lc, int
}
}
/*
* Remove elements being deleted
*/
static List *
RemoveElementsBeingDeleted(List *w)
{
ListCell *lc2;
List *w2;
foreach(lc2, w)
{
HnswCandidate *hc = (HnswCandidate *) lfirst(lc2);
if (list_length(hc->element->heaptids) != 0)
w2 = lappend(w2, hc);
}
return w2;
}
/*
* Algorithm 1 from paper
*/
@@ -901,7 +919,6 @@ HnswInsertElement(HnswElement element, HnswElement entryPoint, Relation index, F
int entryLevel;
Datum q = PointerGetDatum(element->vec);
HnswElement skipElement = existing ? element : NULL;
bool removeEntryPoint;
HnswCandidate *entryCandidate;
/* No neighbors if no entry point */
@@ -912,7 +929,6 @@ HnswInsertElement(HnswElement element, HnswElement entryPoint, Relation index, F
entryCandidate = HnswEntryCandidate(entryPoint, q, index, procinfo, collation, true);
ep = lappend(ep, entryCandidate);
entryLevel = entryPoint->level;
removeEntryPoint = existing && list_length(entryPoint->heaptids) == 0;
/* 1st phase: greedy search to insert level */
for (int lc = entryLevel; lc >= level + 1; lc--)
@@ -932,9 +948,10 @@ HnswInsertElement(HnswElement element, HnswElement entryPoint, Relation index, F
w = HnswSearchLayer(q, ep, efConstruction, lc, index, procinfo, collation, true, skipElement);
/* Remove entry point if it's being deleted */
if (removeEntryPoint)
w = list_delete_ptr(w, entryCandidate);
/* Elements being deleted can help with search */
/* but should be removed before selecting neighbors */
if (index != NULL)
w = RemoveElementsBeingDeleted(w);
neighbors = SelectNeighbors(w, lm, lc, procinfo, collation, NULL);

5
src/hnswvacuum.c
View File

@@ -174,6 +174,11 @@ NeedsUpdated(HnswVacuumState * vacuumstate, HnswElement element)
}
}
/* Also update if layer 0 is not full */
/* This could indicate too many candidates being deleted during insert */
if (!needsUpdated)
needsUpdated = !ItemPointerIsValid(&ntup->indextids[ntup->count - 1]);
UnlockReleaseBuffer(buf);
return needsUpdated;