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Minor tweaking of index special-space definitions so that the various

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index types can be reliably distinguished by examining the special space
on an index page.  Per my earlier proposal, plus the realization that
there's no need for btree's vacuum cycle ID to cycle through every possible
16-bit value.  Restricting its range a little costs nearly nothing and
eliminates the possibility of collisions.
Memo to self: remember to make bitmap indexes play along with this scheme,
assuming that patch ever gets accepted.
This commit is contained in:
Tom Lane
2007-04-09 22:04:08 +00:00
parent 485d9ca96f
commit 56218fbc48
9 changed files with 78 additions and 64 deletions
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20
src/include/access/hash.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.77 2007/04/02 03:49:40 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.78 2007/04/09 22:04:05 tgl Exp $
*
* NOTES
* modeled after Margo Seltzer's hash implementation for unix.
@@ -56,20 +56,18 @@ typedef struct HashPageOpaqueData
BlockNumber hasho_nextblkno; /* next ovfl blkno */
Bucket hasho_bucket; /* bucket number this pg belongs to */
uint16 hasho_flag; /* page type code, see above */
uint16 hasho_filler; /* available for future use */
/*
* We presently set hasho_filler to HASHO_FILL (0x1234); this is for the
* convenience of pg_filedump, which otherwise would have a hard time
* telling HashPageOpaqueData from BTPageOpaqueData. If we ever need that
* space for some other purpose, pg_filedump will have to find another
* way.
*/
uint16 hasho_page_id; /* for identification of hash indexes */
} HashPageOpaqueData;
typedef HashPageOpaqueData *HashPageOpaque;
#define HASHO_FILL 0x1234
/*
* The page ID is for the convenience of pg_filedump and similar utilities,
* which otherwise would have a hard time telling pages of different index
* types apart. It should be the last 2 bytes on the page. This is more or
* less "free" due to alignment considerations.
*/
#define HASHO_PAGE_ID 0xFF80
/*
* HashScanOpaqueData is private state for a hash index scan.