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Avoid unnecessary lseek() calls by cleanups in md.c. mdfd_lstbcnt was

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not being consulted anywhere, so remove it and remove the _mdnblocks()
calls that were used to set it.  Change smgrextend interface to pass in
the target block number (ie, current file length) --- the caller always
knows this already, having already done smgrnblocks(), so it's silly to
do it over again inside mdextend.  Net result: extension of a file now
takes one lseek(SEEK_END) and a write(), not three lseeks and a write.
This commit is contained in:
Tom Lane
2001-05-10 20:38:49 +00:00
parent a26ad8a643
commit 642107d5ba
6 changed files with 129 additions and 106 deletions
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9
src/include/storage/smgr.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: smgr.h,v 1.28 2001/03/22 04:01:09 momjian Exp $
* $Id: smgr.h,v 1.29 2001/05/10 20:38:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -28,7 +28,8 @@
extern int smgrinit(void);
extern int smgrcreate(int16 which, Relation reln);
extern int smgrunlink(int16 which, Relation reln);
extern int smgrextend(int16 which, Relation reln, char *buffer);
extern int smgrextend(int16 which, Relation reln, BlockNumber blocknum,
char *buffer);
extern int smgropen(int16 which, Relation reln, bool failOK);
extern int smgrclose(int16 which, Relation reln);
extern int smgrread(int16 which, Relation reln, BlockNumber blocknum,
@@ -60,7 +61,7 @@ extern void smgr_desc(char *buf, uint8 xl_info, char *rec);
extern int mdinit(void);
extern int mdcreate(Relation reln);
extern int mdunlink(RelFileNode rnode);
extern int mdextend(Relation reln, char *buffer);
extern int mdextend(Relation reln, BlockNumber blocknum, char *buffer);
extern int mdopen(Relation reln);
extern int mdclose(Relation reln);
extern int mdread(Relation reln, BlockNumber blocknum, char *buffer);
@@ -82,7 +83,7 @@ extern SPINLOCK MMCacheLock;
extern int mminit(void);
extern int mmcreate(Relation reln);
extern int mmunlink(RelFileNode rnode);
extern int mmextend(Relation reln, char *buffer);
extern int mmextend(Relation reln, BlockNumber blocknum, char *buffer);
extern int mmopen(Relation reln);
extern int mmclose(Relation reln);
extern int mmread(Relation reln, BlockNumber blocknum, char *buffer);