From 916b2321adb0ac0ef3cca7953fbe6743cc622295 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 25 Jul 2000 04:47:59 +0000
Subject: [PATCH] Clean up and document btree code for ordering keys. Neat
stuff, actually, but who could understand it with no comments? Fix bug while
at it: _bt_orderkeys would try to invoke comparisons on NULL inputs, given
the right sort of redundant quals.
---
src/backend/access/nbtree/nbtsearch.c | 103 ++++----
src/backend/access/nbtree/nbtutils.c | 345 ++++++++++++++++----------
src/include/access/nbtree.h | 27 +-
3 files changed, 284 insertions(+), 191 deletions(-)
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index 49aec3b23d9..8b0804d28eb 100644
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.61 2000/07/21 06:42:32 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.62 2000/07/25 04:47:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -374,7 +374,7 @@ _bt_next(IndexScanDesc scan, ScanDirection dir)
BTItem btitem;
IndexTuple itup;
BTScanOpaque so;
- Size keysok;
+ bool continuescan;
rel = scan->relation;
so = (BTScanOpaque) scan->opaque;
@@ -396,16 +396,14 @@ _bt_next(IndexScanDesc scan, ScanDirection dir)
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
itup = &btitem->bti_itup;
- if (_bt_checkkeys(scan, itup, &keysok))
+ if (_bt_checkkeys(scan, itup, dir, &continuescan))
{
/* tuple passes all scan key conditions, so return it */
- Assert(keysok == so->numberOfKeys);
return FormRetrieveIndexResult(current, &(itup->t_tid));
}
/* This tuple doesn't pass, but there might be more that do */
- } while (keysok >= so->numberOfFirstKeys ||
- (keysok == ((Size) -1) && ScanDirectionIsBackward(dir)));
+ } while (continuescan);
/* No more items, so close down the current-item info */
ItemPointerSetInvalid(current);
@@ -442,11 +440,10 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
RegProcedure proc;
int32 result;
BTScanOpaque so;
- Size keysok;
- bool strategyCheck;
- ScanKey scankeys = 0;
+ bool continuescan;
+ ScanKey scankeys = NULL;
int keysCount = 0;
- int *nKeyIs = 0;
+ int *nKeyIs = NULL;
int i,
j;
StrategyNumber strat_total;
@@ -455,71 +452,74 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
so = (BTScanOpaque) scan->opaque;
/*
- * Order the keys in the qualification and be sure that the scan
- * exploits the tree order.
+ * Order the scan keys in our canonical fashion and eliminate any
+ * redundant keys.
*/
- so->numberOfFirstKeys = 0; /* may be changed by _bt_orderkeys */
- so->qual_ok = 1; /* may be changed by _bt_orderkeys */
- scan->scanFromEnd = false;
- strategyCheck = false;
- if (so->numberOfKeys > 0)
- {
- _bt_orderkeys(rel, so);
+ _bt_orderkeys(rel, so);
- if (so->qual_ok)
- strategyCheck = true;
- }
+ /*
+ * Quit now if _bt_orderkeys() discovered that the scan keys can
+ * never be satisfied (eg, x == 1 AND x > 2).
+ */
+ if (! so->qual_ok)
+ return (RetrieveIndexResult) NULL;
+
+ /*
+ * Examine the scan keys to discover where we need to start the scan.
+ */
+ scan->scanFromEnd = false;
strat_total = BTEqualStrategyNumber;
- if (strategyCheck)
+ if (so->numberOfKeys > 0)
{
- AttrNumber attno;
-
nKeyIs = (int *) palloc(so->numberOfKeys * sizeof(int));
for (i = 0; i < so->numberOfKeys; i++)
{
- attno = so->keyData[i].sk_attno;
- if (attno == keysCount)
+ AttrNumber attno = so->keyData[i].sk_attno;
+
+ /* ignore keys for already-determined attrs */
+ if (attno <= keysCount)
continue;
+ /* if we didn't find a boundary for the preceding attr, quit */
if (attno > keysCount + 1)
break;
strat = _bt_getstrat(rel, attno,
so->keyData[i].sk_procedure);
+ /*
+ * Can we use this key as a starting boundary for this attr?
+ *
+ * We can use multiple keys if they look like, say, = >= =
+ * but we have to stop after accepting a > or < boundary.
+ */
if (strat == strat_total ||
strat == BTEqualStrategyNumber)
{
nKeyIs[keysCount++] = i;
- continue;
}
- if (ScanDirectionIsBackward(dir) &&
- (strat == BTLessStrategyNumber ||
- strat == BTLessEqualStrategyNumber))
+ else if (ScanDirectionIsBackward(dir) &&
+ (strat == BTLessStrategyNumber ||
+ strat == BTLessEqualStrategyNumber))
{
nKeyIs[keysCount++] = i;
strat_total = strat;
if (strat == BTLessStrategyNumber)
break;
- continue;
}
- if (ScanDirectionIsForward(dir) &&
- (strat == BTGreaterStrategyNumber ||
- strat == BTGreaterEqualStrategyNumber))
+ else if (ScanDirectionIsForward(dir) &&
+ (strat == BTGreaterStrategyNumber ||
+ strat == BTGreaterEqualStrategyNumber))
{
nKeyIs[keysCount++] = i;
strat_total = strat;
if (strat == BTGreaterStrategyNumber)
break;
- continue;
}
}
- if (!keysCount)
+ if (keysCount == 0)
scan->scanFromEnd = true;
}
else
scan->scanFromEnd = true;
- if (so->qual_ok == 0)
- return (RetrieveIndexResult) NULL;
-
/* if we just need to walk down one edge of the tree, do that */
if (scan->scanFromEnd)
{
@@ -529,16 +529,14 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
}
/*
- * Okay, we want something more complicated. What we'll do is use the
- * first item in the scan key passed in (which has been correctly
- * ordered to take advantage of index ordering) to position ourselves
- * at the right place in the scan.
+ * We want to start the scan somewhere within the index. Set up a
+ * scankey we can use to search for the correct starting point.
*/
scankeys = (ScanKey) palloc(keysCount * sizeof(ScanKeyData));
for (i = 0; i < keysCount; i++)
{
j = nKeyIs[i];
- /* _bt_orderkeys disallows it, but it's place to add some code latter */
+ /* _bt_orderkeys disallows it, but it's place to add some code later */
if (so->keyData[j].sk_flags & SK_ISNULL)
{
pfree(nKeyIs);
@@ -578,6 +576,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
blkno = BufferGetBlockNumber(buf);
page = BufferGetPage(buf);
+ /* position to the precise item on the page */
offnum = _bt_binsrch(rel, buf, keysCount, scankeys);
ItemPointerSet(current, blkno, offnum);
@@ -595,7 +594,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
* call _bt_endpoint() to set up a scan starting at that index endpoint,
* as appropriate for the desired scan type.
*
- * it's yet other place to add some code latter for is(not)null ...
+ * it's yet other place to add some code later for is(not)null ...
*----------
*/
@@ -737,13 +736,12 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
itup = &btitem->bti_itup;
/* is the first item actually acceptable? */
- if (_bt_checkkeys(scan, itup, &keysok))
+ if (_bt_checkkeys(scan, itup, dir, &continuescan))
{
/* yes, return it */
res = FormRetrieveIndexResult(current, &(itup->t_tid));
}
- else if (keysok >= so->numberOfFirstKeys ||
- (keysok == ((Size) -1) && ScanDirectionIsBackward(dir)))
+ else if (continuescan)
{
/* no, but there might be another one that is */
res = _bt_next(scan, dir);
@@ -906,7 +904,7 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
IndexTuple itup;
BTScanOpaque so;
RetrieveIndexResult res;
- Size keysok;
+ bool continuescan;
rel = scan->relation;
current = &(scan->currentItemData);
@@ -1012,13 +1010,12 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
itup = &(btitem->bti_itup);
/* see if we picked a winner */
- if (_bt_checkkeys(scan, itup, &keysok))
+ if (_bt_checkkeys(scan, itup, dir, &continuescan))
{
/* yes, return it */
res = FormRetrieveIndexResult(current, &(itup->t_tid));
}
- else if (keysok >= so->numberOfFirstKeys ||
- (keysok == ((Size) -1) && ScanDirectionIsBackward(dir)))
+ else if (continuescan)
{
/* no, but there might be another one that is */
res = _bt_next(scan, dir);
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index eb77bfd8dae..7bf527dd44f 100644
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtutils.c,v 1.39 2000/07/21 19:21:00 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtutils.c,v 1.40 2000/07/25 04:47:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -145,88 +145,148 @@ _bt_formitem(IndexTuple itup)
return btitem;
}
-/*
+/*----------
* _bt_orderkeys() -- Put keys in a sensible order for conjunctive quals.
*
- * The order of the keys in the qual match the ordering imposed by
- * the index. This routine only needs to be called if there is
- * more than one qual clause using this index.
+ * After this routine runs, the scan keys are ordered by index attribute
+ * (all quals for attr 1, then all for attr 2, etc) and within each attr
+ * the keys are ordered by constraint type: ">", ">=", "=", "<=", "<".
+ * Furthermore, redundant keys are eliminated: we keep only the tightest
+ * >/>= bound and the tightest </<= bound, and if there's an = key then
+ * that's the only one returned. (So, we return either a single = key,
+ * or one or two boundary-condition keys for each attr.)
+ *
+ * As a byproduct of this work, we can detect contradictory quals such
+ * as "x = 1 AND x > 2". If we see that, we return so->quals_ok = FALSE,
+ * indicating the scan need not be run at all since no tuples can match.
+ *
+ * Another byproduct is to determine how many quals must be satisfied to
+ * continue the scan. _bt_checkkeys uses this. For example, if the quals
+ * are "x = 1 AND y < 4 AND z < 5", then _bt_checkkeys will reject a tuple
+ * (1,2,7), but we must continue the scan in case there are tuples (1,3,z).
+ * But once we reach tuples like (1,4,z) we can stop scanning because no
+ * later tuples could match. This is reflected by setting
+ * so->numberOfRequiredKeys to the number of leading keys that must be
+ * matched to continue the scan. numberOfRequiredKeys is equal to the
+ * number of leading "=" keys plus the key(s) for the first non "="
+ * attribute, which can be seen to be correct by considering the above
+ * example.
+ *
+ * The initial ordering of the keys is expected to be by attribute already
+ * (see group_clauses_by_indexkey() in indxpath.c). The task here is to
+ * standardize the appearance of multiple keys for the same attribute.
+ *
+ * XXX this routine is one of many places that fail to handle SK_COMMUTE
+ * scankeys properly. Currently, the planner is careful never to generate
+ * any indexquals that would require SK_COMMUTE to be set. Someday we ought
+ * to try to fix this, though it's not real critical as long as indexable
+ * operators all have commutators...
+ *
+ * Note: this routine invokes comparison operators via OidFunctionCallN,
+ * ie, without caching function lookups. No point in trying to be smarter,
+ * since these comparisons are executed only when the user expresses a
+ * hokey qualification, and happen only once per scan anyway.
+ *----------
*/
void
_bt_orderkeys(Relation relation, BTScanOpaque so)
{
- ScanKey xform;
- ScanKeyData *cur;
+ ScanKeyData xform[BTMaxStrategyNumber];
+ bool init[BTMaxStrategyNumber];
+ uint16 numberOfKeys = so->numberOfKeys;
+ ScanKey key;
+ ScanKey cur;
StrategyMap map;
- int nbytes;
Datum test;
int i,
j;
- int init[BTMaxStrategyNumber + 1];
- ScanKey key;
- uint16 numberOfKeys = so->numberOfKeys;
- uint16 new_numberOfKeys = 0;
- AttrNumber attno = 1;
- bool equalStrategyEnd,
- underEqualStrategy;
+ AttrNumber attno;
+ uint16 new_numberOfKeys;
+ bool allEqualSoFar;
+
+ so->qual_ok = true;
+ so->numberOfRequiredKeys = 0;
if (numberOfKeys < 1)
- return;
+ return; /* done if qual-less scan */
key = so->keyData;
-
cur = &key[0];
+ /* check input keys are correctly ordered */
if (cur->sk_attno != 1)
elog(ERROR, "_bt_orderkeys: key(s) for attribute 1 missed");
+ /* We can short-circuit most of the work if there's just one key */
if (numberOfKeys == 1)
{
/*
* We don't use indices for 'A is null' and 'A is not null'
- * currently and 'A < = > <> NULL' is non-sense' - so qual is not
- * Ok. - vadim 03/21/97
+ * currently and 'A < = > <> NULL' will always fail - so qual is
+ * not Ok if comparison value is NULL. - vadim 03/21/97
*/
if (cur->sk_flags & SK_ISNULL)
- so->qual_ok = 0;
- so->numberOfFirstKeys = 1;
+ so->qual_ok = false;
+ so->numberOfRequiredKeys = 1;
return;
}
- /* get space for the modified array of keys */
- nbytes = BTMaxStrategyNumber * sizeof(ScanKeyData);
- xform = (ScanKey) palloc(nbytes);
-
- MemSet(xform, 0, nbytes);
+ /*
+ * Otherwise, do the full set of pushups.
+ */
+ new_numberOfKeys = 0;
+ allEqualSoFar = true;
+
+ /*
+ * Initialize for processing of keys for attr 1.
+ *
+ * xform[i] holds a copy of the current scan key of strategy type i+1,
+ * if any; init[i] is TRUE if we have found such a key for this attr.
+ */
+ attno = 1;
map = IndexStrategyGetStrategyMap(RelationGetIndexStrategy(relation),
BTMaxStrategyNumber,
attno);
- for (j = 0; j <= BTMaxStrategyNumber; j++)
- init[j] = 0;
-
- equalStrategyEnd = false;
- underEqualStrategy = true;
- /* check each key passed in */
- for (i = 0;;)
+ MemSet(xform, 0, sizeof(xform)); /* not really necessary */
+ MemSet(init, 0, sizeof(init));
+
+ /*
+ * Loop iterates from 0 to numberOfKeys inclusive; we use the last
+ * pass to handle after-last-key processing. Actual exit from the
+ * loop is at the "break" statement below.
+ */
+ for (i = 0; ; cur++, i++)
{
if (i < numberOfKeys)
- cur = &key[i];
-
- if (cur->sk_flags & SK_ISNULL) /* see comments above */
- so->qual_ok = 0;
+ {
+ /* See comments above: any NULL implies cannot match qual */
+ if (cur->sk_flags & SK_ISNULL)
+ {
+ so->qual_ok = false;
+ /* Quit processing so we don't try to invoke comparison
+ * routines on NULLs.
+ */
+ return;
+ }
+ }
+ /*
+ * If we are at the end of the keys for a particular attr,
+ * finish up processing and emit the cleaned-up keys.
+ */
if (i == numberOfKeys || cur->sk_attno != attno)
{
- if (cur->sk_attno != attno + 1 && i < numberOfKeys)
+ bool priorAllEqualSoFar = allEqualSoFar;
+
+ /* check input keys are correctly ordered */
+ if (i < numberOfKeys && cur->sk_attno != attno + 1)
elog(ERROR, "_bt_orderkeys: key(s) for attribute %d missed",
attno + 1);
- underEqualStrategy = (!equalStrategyEnd);
-
/*
* If = has been specified, no other key will be used. In case
- * of key < 2 && key == 1 and so on we have to set qual_ok to
- * 0
+ * of key > 2 && key == 1 and so on we have to set qual_ok to
+ * false before discarding the other keys.
*/
if (init[BTEqualStrategyNumber - 1])
{
@@ -236,187 +296,222 @@ _bt_orderkeys(Relation relation, BTScanOpaque so)
eq = &xform[BTEqualStrategyNumber - 1];
for (j = BTMaxStrategyNumber; --j >= 0;)
{
- if (j == (BTEqualStrategyNumber - 1) || init[j] == 0)
+ if (! init[j] ||
+ j == (BTEqualStrategyNumber - 1))
continue;
chk = &xform[j];
test = OidFunctionCall2(chk->sk_procedure,
- eq->sk_argument, chk->sk_argument);
+ eq->sk_argument,
+ chk->sk_argument);
if (!DatumGetBool(test))
- so->qual_ok = 0;
+ so->qual_ok = false;
}
- init[BTLessStrategyNumber - 1] = 0;
- init[BTLessEqualStrategyNumber - 1] = 0;
- init[BTGreaterEqualStrategyNumber - 1] = 0;
- init[BTGreaterStrategyNumber - 1] = 0;
+ init[BTLessStrategyNumber - 1] = false;
+ init[BTLessEqualStrategyNumber - 1] = false;
+ init[BTGreaterEqualStrategyNumber - 1] = false;
+ init[BTGreaterStrategyNumber - 1] = false;
}
else
- equalStrategyEnd = true;
+ {
+ /*
+ * No "=" for this key, so we're done with required keys
+ */
+ allEqualSoFar = false;
+ }
- /* only one of <, <= */
+ /* keep only one of <, <= */
if (init[BTLessStrategyNumber - 1]
&& init[BTLessEqualStrategyNumber - 1])
{
- ScanKeyData *lt,
- *le;
+ ScanKeyData *lt = &xform[BTLessStrategyNumber - 1];
+ ScanKeyData *le = &xform[BTLessEqualStrategyNumber - 1];
- lt = &xform[BTLessStrategyNumber - 1];
- le = &xform[BTLessEqualStrategyNumber - 1];
-
- /*
- * DO NOT use the cached function stuff here -- this is
- * key ordering, happens only when the user expresses a
- * hokey qualification, and gets executed only once,
- * anyway. The transform maps are hard-coded, and can't
- * be initialized in the correct way.
- */
test = OidFunctionCall2(le->sk_procedure,
- lt->sk_argument, le->sk_argument);
+ lt->sk_argument,
+ le->sk_argument);
if (DatumGetBool(test))
- init[BTLessEqualStrategyNumber - 1] = 0;
+ init[BTLessEqualStrategyNumber - 1] = false;
else
- init[BTLessStrategyNumber - 1] = 0;
+ init[BTLessStrategyNumber - 1] = false;
}
- /* only one of >, >= */
+ /* keep only one of >, >= */
if (init[BTGreaterStrategyNumber - 1]
&& init[BTGreaterEqualStrategyNumber - 1])
{
- ScanKeyData *gt,
- *ge;
-
- gt = &xform[BTGreaterStrategyNumber - 1];
- ge = &xform[BTGreaterEqualStrategyNumber - 1];
+ ScanKeyData *gt = &xform[BTGreaterStrategyNumber - 1];
+ ScanKeyData *ge = &xform[BTGreaterEqualStrategyNumber - 1];
- /* see note above on function cache */
test = OidFunctionCall2(ge->sk_procedure,
- gt->sk_argument, ge->sk_argument);
+ gt->sk_argument,
+ ge->sk_argument);
if (DatumGetBool(test))
- init[BTGreaterEqualStrategyNumber - 1] = 0;
+ init[BTGreaterEqualStrategyNumber - 1] = false;
else
- init[BTGreaterStrategyNumber - 1] = 0;
+ init[BTGreaterStrategyNumber - 1] = false;
}
- /* okay, reorder and count */
+ /*
+ * Emit the cleaned-up keys back into the key[] array in the
+ * correct order. Note we are overwriting our input here!
+ * It's OK because (a) xform[] is a physical copy of the keys
+ * we want, (b) we cannot emit more keys than we input, so
+ * we won't overwrite as-yet-unprocessed keys.
+ */
for (j = BTMaxStrategyNumber; --j >= 0;)
+ {
if (init[j])
- key[new_numberOfKeys++] = xform[j];
+ memcpy(&key[new_numberOfKeys++], &xform[j],
+ sizeof(ScanKeyData));
+ }
- if (underEqualStrategy)
- so->numberOfFirstKeys = new_numberOfKeys;
+ /*
+ * If all attrs before this one had "=", include these keys
+ * into the required-keys count.
+ */
+ if (priorAllEqualSoFar)
+ so->numberOfRequiredKeys = new_numberOfKeys;
+ /*
+ * Exit loop here if done.
+ */
if (i == numberOfKeys)
break;
- /* initialization for new attno */
+ /* Re-initialize for new attno */
attno = cur->sk_attno;
- MemSet(xform, 0, nbytes);
map = IndexStrategyGetStrategyMap(RelationGetIndexStrategy(relation),
BTMaxStrategyNumber,
attno);
- /* haven't looked at any strategies yet */
- for (j = 0; j <= BTMaxStrategyNumber; j++)
- init[j] = 0;
+ MemSet(xform, 0, sizeof(xform)); /* not really necessary */
+ MemSet(init, 0, sizeof(init));
}
+ /*
+ * OK, figure out which strategy this key corresponds to
+ */
for (j = BTMaxStrategyNumber; --j >= 0;)
{
if (cur->sk_procedure == map->entry[j].sk_procedure)
break;
}
+ if (j < 0)
+ elog(ERROR, "_bt_orderkeys: unable to identify operator %u",
+ cur->sk_procedure);
/* have we seen one of these before? */
if (init[j])
{
- /* yup, use the appropriate value */
+ /* yup, keep the more restrictive value */
test = FunctionCall2(&cur->sk_func,
- cur->sk_argument, xform[j].sk_argument);
+ cur->sk_argument,
+ xform[j].sk_argument);
if (DatumGetBool(test))
xform[j].sk_argument = cur->sk_argument;
else if (j == (BTEqualStrategyNumber - 1))
- so->qual_ok = 0;/* key == a && key == b, but a != b */
+ so->qual_ok = false; /* key == a && key == b, but a != b */
}
else
{
- /* nope, use this value */
- memmove(&xform[j], cur, sizeof(*cur));
- init[j] = 1;
+ /* nope, so remember this scankey */
+ memcpy(&xform[j], cur, sizeof(ScanKeyData));
+ init[j] = true;
}
-
- i++;
}
so->numberOfKeys = new_numberOfKeys;
-
- pfree(xform);
}
/*
- * Test whether an indextuple satisfies all the scankey conditions
- *
- * If not ("false" return), the number of conditions satisfied is
- * returned in *keysok. Given proper ordering of the scankey conditions,
- * we can use this to determine whether it's worth continuing the scan.
- * See _bt_orderkeys().
+ * Test whether an indextuple satisfies all the scankey conditions.
*
- * HACK: *keysok == (Size) -1 means we stopped evaluating because we found
- * a NULL value in the index tuple. It's not quite clear to me why this
- * case has to be treated specially --- tgl 7/00.
+ * If the tuple fails to pass the qual, we also determine whether there's
+ * any need to continue the scan beyond this tuple, and set *continuescan
+ * accordingly. See comments for _bt_orderkeys(), above, about how this is
+ * done.
*/
bool
-_bt_checkkeys(IndexScanDesc scan, IndexTuple tuple, Size *keysok)
+_bt_checkkeys(IndexScanDesc scan, IndexTuple tuple,
+ ScanDirection dir, bool *continuescan)
{
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Size keysz = so->numberOfKeys;
TupleDesc tupdesc;
ScanKey key;
- Datum datum;
- bool isNull;
- Datum test;
+ Size keysok;
+
+ *continuescan = true;
- *keysok = 0;
+ /* If no keys, always scan the whole index */
if (keysz == 0)
return true;
- key = so->keyData;
tupdesc = RelationGetDescr(scan->relation);
+ key = so->keyData;
+ keysok = 0;
IncrIndexProcessed();
while (keysz > 0)
{
+ Datum datum;
+ bool isNull;
+ Datum test;
+
datum = index_getattr(tuple,
- key[0].sk_attno,
+ key->sk_attno,
tupdesc,
&isNull);
/* btree doesn't support 'A is null' clauses, yet */
- if (key[0].sk_flags & SK_ISNULL)
- return false;
- if (isNull)
+ if (key->sk_flags & SK_ISNULL)
{
- if (*keysok < so->numberOfFirstKeys)
- *keysok = -1;
+ /* we shouldn't get here, really; see _bt_orderkeys() */
+ *continuescan = false;
return false;
}
- if (key[0].sk_flags & SK_COMMUTE)
+ if (isNull)
{
- test = FunctionCall2(&key[0].sk_func,
- key[0].sk_argument, datum);
+ /*
+ * Since NULLs are sorted after non-NULLs, we know we have
+ * reached the upper limit of the range of values for this
+ * index attr. On a forward scan, we can stop if this qual
+ * is one of the "must match" subset. On a backward scan,
+ * however, we should keep going.
+ */
+ if (keysok < so->numberOfRequiredKeys &&
+ ScanDirectionIsForward(dir))
+ *continuescan = false;
+ /*
+ * In any case, this indextuple doesn't match the qual.
+ */
+ return false;
}
+
+ if (key->sk_flags & SK_COMMUTE)
+ test = FunctionCall2(&key->sk_func,
+ key->sk_argument, datum);
else
- {
- test = FunctionCall2(&key[0].sk_func,
- datum, key[0].sk_argument);
- }
+ test = FunctionCall2(&key->sk_func,
+ datum, key->sk_argument);
- if (DatumGetBool(test) == !!(key[0].sk_flags & SK_NEGATE))
+ if (DatumGetBool(test) == !!(key->sk_flags & SK_NEGATE))
+ {
+ /*
+ * Tuple fails this qual. If it's a required qual, then
+ * we can conclude no further tuples will pass, either.
+ */
+ if (keysok < so->numberOfRequiredKeys)
+ *continuescan = false;
return false;
+ }
- (*keysok)++;
+ keysok++;
key++;
keysz--;
}
+ /* If we get here, the tuple passes all quals. */
return true;
}
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 3f8eebc3b36..d84cfa5ded9 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: nbtree.h,v 1.39 2000/07/21 06:42:35 tgl Exp $
+ * $Id: nbtree.h,v 1.40 2000/07/25 04:47:57 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -47,13 +47,12 @@ typedef struct BTPageOpaqueData
typedef BTPageOpaqueData *BTPageOpaque;
/*
- * ScanOpaqueData is used to remember which buffers we're currently
- * examining in the scan. We keep these buffers locked and pinned
- * and recorded in the opaque entry of the scan in order to avoid
- * doing a ReadBuffer() for every tuple in the index. This avoids
- * semop() calls, which are expensive.
+ * BTScanOpaqueData is used to remember which buffers we're currently
+ * examining in the scan. We keep these buffers pinned (but not locked,
+ * see nbtree.c) and recorded in the opaque entry of the scan to avoid
+ * doing a ReadBuffer() for every tuple in the index.
*
- * And it's used to remember actual scankey info (we need in it
+ * And it's used to remember actual scankey info (we need it
* if some scankeys evaled at runtime).
*
* curHeapIptr & mrkHeapIptr are heap iptr-s from current/marked
@@ -69,11 +68,12 @@ typedef struct BTScanOpaqueData
Buffer btso_mrkbuf;
ItemPointerData curHeapIptr;
ItemPointerData mrkHeapIptr;
- uint16 qual_ok; /* 0 for quals like key == 1 && key > 2 */
- uint16 numberOfKeys; /* number of keys */
- uint16 numberOfFirstKeys; /* number of keys for 1st
- * attribute */
- ScanKey keyData; /* key descriptor */
+ /* these fields are set by _bt_orderkeys(), which see for more info: */
+ bool qual_ok; /* false if qual can never be satisfied */
+ uint16 numberOfKeys; /* number of scan keys */
+ uint16 numberOfRequiredKeys; /* number of keys that must be matched
+ * to continue the scan */
+ ScanKey keyData; /* array of scan keys */
} BTScanOpaqueData;
typedef BTScanOpaqueData *BTScanOpaque;
@@ -276,7 +276,8 @@ extern ScanKey _bt_mkscankey_nodata(Relation rel);
extern void _bt_freeskey(ScanKey skey);
extern void _bt_freestack(BTStack stack);
extern void _bt_orderkeys(Relation relation, BTScanOpaque so);
-extern bool _bt_checkkeys(IndexScanDesc scan, IndexTuple tuple, Size *keysok);
+extern bool _bt_checkkeys(IndexScanDesc scan, IndexTuple tuple,
+ ScanDirection dir, bool *continuescan);
extern BTItem _bt_formitem(IndexTuple itup);
/*
--
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