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Postgres FD Implementation
Commit 916b2321 authored by Tom Lane's avatar Tom Lane
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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.
parent da1ad323
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Showing with 284 additions and 191 deletions
src/backend/access/nbtree/nbtsearch.c
View file @ 916b2321
......@@ -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;
......@@ -455,42 +452,50 @@ _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);
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) &&
else if (ScanDirectionIsBackward(dir) &&
(strat == BTLessStrategyNumber ||
strat == BTLessEqualStrategyNumber))
{
......@@ -498,9 +503,8 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
strat_total = strat;
if (strat == BTLessStrategyNumber)
break;
continue;
}
if (ScanDirectionIsForward(dir) &&
else if (ScanDirectionIsForward(dir) &&
(strat == BTGreaterStrategyNumber ||
strat == BTGreaterEqualStrategyNumber))
{
......@@ -508,18 +512,14 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
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);
......
src/backend/access/nbtree/nbtutils.c
View file @ 916b2321
This diff is collapsed.
src/include/access/nbtree.h
View file @ 916b2321
......@@ -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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