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Clean up and document btree code for ordering keys. Neat stuff,

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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.
This commit is contained in:
Tom Lane
2000-07-25 04:47:59 +00:00
parent da1ad323b7
commit 916b2321ad
3 changed files with 282 additions and 189 deletions
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27
src/include/access/nbtree.h
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@@ -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);
/*