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Instead of using a numberOfRequiredKeys count to distinguish required

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and non-required keys in a btree index scan, mark the required scankeys
with private flag bits SK_BT_REQFWD and/or SK_BT_REQBKWD.  This seems
at least marginally clearer to me, and it eliminates a wired-into-the-
data-structure assumption that required keys are consecutive.  Even though
that assumption will remain true for the foreseeable future, having it
in there makes the code seem more complex than necessary.
This commit is contained in:
Tom Lane
2006-01-23 22:31:41 +00:00
parent f6f43e7ee3
commit 7ccaf13a06
3 changed files with 92 additions and 74 deletions
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22
src/include/access/nbtree.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.89 2005/12/07 19:37:53 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.90 2006/01/23 22:31:41 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -368,16 +368,15 @@ typedef BTStackData *BTStack;
/*
* 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
* examining in an indexscan. Between calls to btgettuple or btgetmulti,
* we keep these buffers pinned (but not locked, see nbtree.c) to avoid
* doing a ReadBuffer() for every tuple in the index.
*
* And it's used to remember actual scankey info (we need it
* if some scankeys evaled at runtime).
* We also store preprocessed versions of the scan keys in this structure.
* See _bt_preprocess_keys() for details of the preprocessing.
*
* curHeapIptr & mrkHeapIptr are heap iptr-s from current/marked
* index tuples: we don't adjust scans on insertions (and, if LLL
* is ON, don't hold locks on index pages between passes) - we
* index tuples: we don't adjust scans on insertions - instead we
* use these pointers to restore index scan positions...
* - vadim 07/29/98
*/
@ -391,13 +390,18 @@ typedef struct BTScanOpaqueData
/* these fields are set by _bt_preprocess_keys(): */
bool qual_ok; /* false if qual can never be satisfied */
int numberOfKeys; /* number of preprocessed scan keys */
int numberOfRequiredKeys; /* number of keys that must be matched
* to continue the scan */
ScanKey keyData; /* array of preprocessed scan keys */
} BTScanOpaqueData;
typedef BTScanOpaqueData *BTScanOpaque;
/*
* We use these private sk_flags bits in preprocessed scan keys
*/
#define SK_BT_REQFWD 0x00010000 /* required to continue forward scan */
#define SK_BT_REQBKWD 0x00020000 /* required to continue backward scan */
/*
* prototypes for functions in nbtree.c (external entry points for btree)
*/