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Fix handling of NULL distances in KNN-GiST 

In order to implement NULL LAST semantic GiST previously assumed distance to
the NULL value to be Inf.  However, our distance functions can return Inf and
NaN for non-null values.  In such cases, NULL LAST semantic appears to be
broken.  This commit fixes that by introducing separate array of null flags for
distances.

Backpatch to all supported versions.

Discussion: https://postgr.es/m/CAPpHfdsNvNdA0DBS%2BwMpFrgwT6C3-q50sFVGLSiuWnV3FqOJuQ%40mail.gmail.com
Author: Alexander Korotkov
Backpatch-through: 9.4
This commit is contained in:
Alexander Korotkov 2019-09-08 21:13:40 +03:00
parent 986319d467
commit 3c155bafa5
3 changed files with 95 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

77
src/backend/access/gist/gistget.c
View File

@ -38,8 +38,9 @@
* Similarly, *recheck_distances_p is set to indicate whether the distances
* need to be rechecked, and it is also ignored for non-leaf entries.
*
* If we are doing an ordered scan, so->distances[] is filled with distance
* data from the distance() functions before returning success.
* If we are doing an ordered scan, so->distancesValues[] and
* so->distancesNulls[] is filled with distance data from the distance()
* functions before returning success.
*
* We must decompress the key in the IndexTuple before passing it to the
* sk_funcs (which actually are the opclass Consistent or Distance methods).
@ -60,7 +61,8 @@ gistindex_keytest(IndexScanDesc scan,
GISTSTATE *giststate = so->giststate;
ScanKey key = scan->keyData;
int keySize = scan->numberOfKeys;
double *distance_p;
double *distance_value_p;
bool *distance_null_p;
Relation r = scan->indexRelation;
*recheck_p = false;
@ -78,7 +80,10 @@ gistindex_keytest(IndexScanDesc scan,
if (GistPageIsLeaf(page)) /* shouldn't happen */
elog(ERROR, "invalid GiST tuple found on leaf page");
for (i = 0; i < scan->numberOfOrderBys; i++)
so->distances[i] = -get_float8_infinity();
{
so->distanceValues[i] = -get_float8_infinity();
so->distanceNulls[i] = false;
}
return true;
}
@ -161,7 +166,8 @@ gistindex_keytest(IndexScanDesc scan,
/* OK, it passes --- now let's compute the distances */
key = scan->orderByData;
distance_p = so->distances;
distance_value_p = so->distanceValues;
distance_null_p = so->distanceNulls;
keySize = scan->numberOfOrderBys;
while (keySize > 0)
{
@ -175,8 +181,9 @@ gistindex_keytest(IndexScanDesc scan,
if ((key->sk_flags & SK_ISNULL) || isNull)
{
/* Assume distance computes as null and sorts to the end */
*distance_p = get_float8_infinity();
/* Assume distance computes as null */
*distance_value_p = 0.0;
*distance_null_p = true;
}
else
{
@ -213,11 +220,13 @@ gistindex_keytest(IndexScanDesc scan,
ObjectIdGetDatum(key->sk_subtype),
PointerGetDatum(&recheck));
*recheck_distances_p |= recheck;
*distance_p = DatumGetFloat8(dist);
*distance_value_p = DatumGetFloat8(dist);
*distance_null_p = false;
}
key++;
distance_p++;
distance_value_p++;
distance_null_p++;
keySize--;
}
@ -230,7 +239,8 @@ gistindex_keytest(IndexScanDesc scan,
*
* scan: index scan we are executing
* pageItem: search queue item identifying an index page to scan
* myDistances: distances array associated with pageItem, or NULL at the root
* myDistanceValues: distances array associated with pageItem, or NULL at the root
* myDistanceNulls: null flags for myDistanceValues array, or NULL at the root
* tbm: if not NULL, gistgetbitmap's output bitmap
* ntids: if not NULL, gistgetbitmap's output tuple counter
*
@ -247,7 +257,8 @@ gistindex_keytest(IndexScanDesc scan,
* sibling will be processed next.
*/
static void
gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem,
double *myDistanceValues, bool *myDistanceNulls,
TIDBitmap *tbm, int64 *ntids)
{
GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
@ -283,7 +294,7 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
GISTSearchItem *item;
/* This can't happen when starting at the root */
Assert(myDistances != NULL);
Assert(myDistanceValues != NULL && myDistanceNulls != NULL);
oldcxt = MemoryContextSwitchTo(so->queueCxt);
@ -293,8 +304,10 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
item->data.parentlsn = pageItem->data.parentlsn;
/* Insert it into the queue using same distances as for this page */
memcpy(item->distances, myDistances,
sizeof(double) * scan->numberOfOrderBys);
memcpy(GISTSearchItemDistanceValues(item, scan->numberOfOrderBys),
myDistanceValues, sizeof(double) * scan->numberOfOrderBys);
memcpy(GISTSearchItemDistanceNulls(item, scan->numberOfOrderBys),
myDistanceNulls, sizeof(bool) * scan->numberOfOrderBys);
pairingheap_add(so->queue, &item->phNode);
@ -370,6 +383,7 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
* search.
*/
GISTSearchItem *item;
int nOrderBys = scan->numberOfOrderBys;
oldcxt = MemoryContextSwitchTo(so->queueCxt);
@ -404,8 +418,10 @@ gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem, double *myDistances,
}
/* Insert it into the queue using new distance data */
memcpy(item->distances, so->distances,
sizeof(double) * scan->numberOfOrderBys);
memcpy(GISTSearchItemDistanceValues(item, nOrderBys),
so->distanceValues, sizeof(double) * nOrderBys);
memcpy(GISTSearchItemDistanceNulls(item, nOrderBys),
so->distanceNulls, sizeof(bool) * nOrderBys);
pairingheap_add(so->queue, &item->phNode);
@ -460,6 +476,8 @@ getNextNearest(IndexScanDesc scan)
do
{
GISTSearchItem *item = getNextGISTSearchItem(so);
float8 *distanceValues = GISTSearchItemDistanceValues(item, scan->numberOfOrderBys);
bool *distanceNulls = GISTSearchItemDistanceNulls(item, scan->numberOfOrderBys);
if (!item)
break;
@ -479,8 +497,8 @@ getNextNearest(IndexScanDesc scan)
if (!scan->xs_orderbynulls[i])
pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
#endif
scan->xs_orderbyvals[i] = Float8GetDatum(item->distances[i]);
scan->xs_orderbynulls[i] = false;
scan->xs_orderbyvals[i] = Float8GetDatum(distanceValues[i]);
scan->xs_orderbynulls[i] = distanceNulls[i];
}
else if (so->orderByTypes[i] == FLOAT4OID)
{
@ -490,8 +508,8 @@ getNextNearest(IndexScanDesc scan)
if (!scan->xs_orderbynulls[i])
pfree(DatumGetPointer(scan->xs_orderbyvals[i]));
#endif
scan->xs_orderbyvals[i] = Float4GetDatum((float4) item->distances[i]);
scan->xs_orderbynulls[i] = false;
scan->xs_orderbyvals[i] = Float4GetDatum(distanceValues[i]);
scan->xs_orderbynulls[i] = distanceNulls[i];
}
else
{
@ -519,7 +537,10 @@ getNextNearest(IndexScanDesc scan)
/* visit an index page, extract its items into queue */
CHECK_FOR_INTERRUPTS();
gistScanPage(scan, item, item->distances, NULL, NULL);
gistScanPage(scan, item,
GISTSearchItemDistanceValues(item, scan->numberOfOrderBys),
GISTSearchItemDistanceNulls(item, scan->numberOfOrderBys),
NULL, NULL);
}
pfree(item);
@ -559,7 +580,7 @@ gistgettuple(PG_FUNCTION_ARGS)
fakeItem.blkno = GIST_ROOT_BLKNO;
memset(&fakeItem.data.parentlsn, 0, sizeof(GistNSN));
gistScanPage(scan, &fakeItem, NULL, NULL, NULL);
gistScanPage(scan, &fakeItem, NULL, NULL, NULL, NULL);
}
if (scan->numberOfOrderBys > 0)
@ -604,7 +625,10 @@ gistgettuple(PG_FUNCTION_ARGS)
* this page, we fall out of the inner "do" and loop around to
* return them.
*/
gistScanPage(scan, item, item->distances, NULL, NULL);
gistScanPage(scan, item,
GISTSearchItemDistanceValues(item, scan->numberOfOrderBys),
GISTSearchItemDistanceNulls(item, scan->numberOfOrderBys),
NULL, NULL);
pfree(item);
} while (so->nPageData == 0);
@ -637,7 +661,7 @@ gistgetbitmap(PG_FUNCTION_ARGS)
fakeItem.blkno = GIST_ROOT_BLKNO;
memset(&fakeItem.data.parentlsn, 0, sizeof(GistNSN));
gistScanPage(scan, &fakeItem, NULL, tbm, &ntids);
gistScanPage(scan, &fakeItem, NULL, NULL, tbm, &ntids);
/*
* While scanning a leaf page, ItemPointers of matching heap tuples will
@ -652,7 +676,10 @@ gistgetbitmap(PG_FUNCTION_ARGS)
CHECK_FOR_INTERRUPTS();
gistScanPage(scan, item, item->distances, tbm, &ntids);
gistScanPage(scan, item,
GISTSearchItemDistanceValues(item, scan->numberOfOrderBys),
GISTSearchItemDistanceNulls(item, scan->numberOfOrderBys),
tbm, &ntids);
pfree(item);
}

25
src/backend/access/gist/gistscan.c
View File

@ -33,14 +33,30 @@ pairingheap_GISTSearchItem_cmp(const pairingheap_node *a, const pairingheap_node
const GISTSearchItem *sb = (const GISTSearchItem *) b;
IndexScanDesc scan = (IndexScanDesc) arg;
int i;
double *da = GISTSearchItemDistanceValues(sa, scan->numberOfOrderBys),
*db = GISTSearchItemDistanceValues(sb, scan->numberOfOrderBys);
bool *na = GISTSearchItemDistanceNulls(sa, scan->numberOfOrderBys),
*nb = GISTSearchItemDistanceNulls(sb, scan->numberOfOrderBys);
/* Order according to distance comparison */
for (i = 0; i < scan->numberOfOrderBys; i++)
{
int cmp = -float8_cmp_internal(sa->distances[i], sb->distances[i]);
if (na[i])
{
if (!nb[i])
return -1;
}
else if (nb[i])
{
return 1;
}
else
{
int cmp = -float8_cmp_internal(da[i], db[i]);
if (cmp != 0)
return cmp;
if (cmp != 0)
return cmp;
}
}
/* Heap items go before inner pages, to ensure a depth-first search */
@ -87,7 +103,8 @@ gistbeginscan(PG_FUNCTION_ARGS)
so->queueCxt = giststate->scanCxt; /* see gistrescan */
/* workspaces with size dependent on numberOfOrderBys: */
so->distances = palloc(sizeof(double) * scan->numberOfOrderBys);
so->distanceValues = palloc(sizeof(double) * scan->numberOfOrderBys);
so->distanceNulls = palloc(sizeof(bool) * scan->numberOfOrderBys);
so->qual_ok = true; /* in case there are zero keys */
if (scan->numberOfOrderBys > 0)
{

26
src/include/access/gist_private.h
View File

@ -133,13 +133,30 @@ typedef struct GISTSearchItem
/* we must store parentlsn to detect whether a split occurred */
GISTSearchHeapItem heap; /* heap info, if heap tuple */
} data;
double distances[FLEXIBLE_ARRAY_MEMBER]; /* numberOfOrderBys
* entries */
/*
* This data structure is followed by arrays of distance values and
* distance null flags. Size of both arrays is
* IndexScanDesc->numberOfOrderBys. See macros below for accessing those
* arrays.
*/
} GISTSearchItem;
#define GISTSearchItemIsHeap(item) ((item).blkno == InvalidBlockNumber)
#define SizeOfGISTSearchItem(n_distances) (offsetof(GISTSearchItem, distances) + sizeof(double) * (n_distances))
#define SizeOfGISTSearchItem(n_distances) (DOUBLEALIGN(sizeof(GISTSearchItem)) + \
(sizeof(double) + sizeof(bool)) * (n_distances))
/*
* We actually don't need n_distances compute pointer to distance values.
* Nevertheless take n_distances as argument to have same arguments list for
* GISTSearchItemDistanceValues() and GISTSearchItemDistanceNulls().
*/
#define GISTSearchItemDistanceValues(item, n_distances) \
((double *) ((Pointer) (item) + DOUBLEALIGN(sizeof(GISTSearchItem))))
#define GISTSearchItemDistanceNulls(item, n_distances) \
((bool *) ((Pointer) (item) + DOUBLEALIGN(sizeof(GISTSearchItem)) + sizeof(double) * (n_distances)))
/*
* GISTScanOpaqueData: private state for a scan of a GiST index
@ -155,7 +172,8 @@ typedef struct GISTScanOpaqueData
bool firstCall; /* true until first gistgettuple call */
/* pre-allocated workspace arrays */
double *distances; /* output area for gistindex_keytest */
double *distanceValues; /* output area for gistindex_keytest */
bool *distanceNulls;
/* In a non-ordered search, returnable heap items are stored here: */
GISTSearchHeapItem pageData[BLCKSZ / sizeof(IndexTupleData)];