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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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22
src/backend/storage/smgr/smgr.c
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@@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.48 2001/03/22 03:59:47 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.49 2001/05/10 20:38:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -30,17 +30,18 @@ typedef struct f_smgr
int (*smgr_shutdown) (void); /* may be NULL */
int (*smgr_create) (Relation reln);
int (*smgr_unlink) (RelFileNode rnode);
int (*smgr_extend) (Relation reln, char *buffer);
int (*smgr_extend) (Relation reln, BlockNumber blocknum,
char *buffer);
int (*smgr_open) (Relation reln);
int (*smgr_close) (Relation reln);
int (*smgr_read) (Relation reln, BlockNumber blocknum,
char *buffer);
char *buffer);
int (*smgr_write) (Relation reln, BlockNumber blocknum,
char *buffer);
char *buffer);
int (*smgr_flush) (Relation reln, BlockNumber blocknum,
char *buffer);
char *buffer);
int (*smgr_blindwrt) (RelFileNode rnode, BlockNumber blkno,
char *buffer, bool dofsync);
char *buffer, bool dofsync);
int (*smgr_markdirty) (Relation reln, BlockNumber blkno);
int (*smgr_blindmarkdirty) (RelFileNode, BlockNumber blkno);
int (*smgr_nblocks) (Relation reln);
@@ -227,15 +228,20 @@ smgrunlink(int16 which, Relation reln)
/*
* smgrextend() -- Add a new block to a file.
*
* The semantics are basically the same as smgrwrite(): write at the
* specified position. However, we are expecting to extend the
* relation (ie, blocknum is the current EOF), and so in case of
* failure we clean up by truncating.
*
* Returns SM_SUCCESS on success; aborts the current transaction on
* failure.
*/
int
smgrextend(int16 which, Relation reln, char *buffer)
smgrextend(int16 which, Relation reln, BlockNumber blocknum, char *buffer)
{
int status;
status = (*(smgrsw[which].smgr_extend)) (reln, buffer);
status = (*(smgrsw[which].smgr_extend)) (reln, blocknum, buffer);
if (status == SM_FAIL)
elog(ERROR, "cannot extend %s: %m.\n\tCheck free disk space.",