From a194574ddee4dd1876835516aed2f4fbd7a4a4c7 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Wed, 14 Jun 2000 03:19:24 +0000
Subject: [PATCH] > If read or write fails. Position will left the same. This >
situation is already tracked in File routines, but a little bit >
incorrectly.
> After small survey in Linux kernel code, I am not sure about
> it. New patch set pos to unknown in the case of read/write
> fails. And do lseek again.
> Here is the full patch for this. This patch reduce amount of
> lseek call ten ti mes for update statement and twenty times for
> select statement. I tested joined up date and count(*) select
> for table with rows > 170000 and 10 indices. I think this is
> worse of trying. Before lseek calls account for more than 5% o
> f time. Now they are 0.89 and 0.15 respectevly.
>
> Due to only one file modification patch should be applied in
> src/backedn/stora ge/file/ dir.
-- Sincerely Yours,
Denis Perchine
---
src/backend/storage/file/fd.c | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index fdb2fc57a59..b8ad36d0162 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.59 2000/06/02 15:57:24 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.60 2000/06/14 03:19:24 momjian Exp $
*
* NOTES:
*
@@ -95,6 +95,8 @@
#define FileIsNotOpen(file) (VfdCache[file].fd == VFD_CLOSED)
+#define FileUnknownPos (-1)
+
typedef struct vfd
{
signed short fd; /* current FD, or VFD_CLOSED if none */
@@ -790,6 +792,8 @@ FileRead(File file, char *buffer, int amount)
returnCode = read(VfdCache[file].fd, buffer, amount);
if (returnCode > 0)
VfdCache[file].seekPos += returnCode;
+ else
+ VfdCache[file].seekPos = FileUnknownPos;
return returnCode;
}
@@ -806,11 +810,12 @@ FileWrite(File file, char *buffer, int amount)
FileAccess(file);
returnCode = write(VfdCache[file].fd, buffer, amount);
- if (returnCode > 0)
+ if (returnCode > 0) {
VfdCache[file].seekPos += returnCode;
-
/* mark the file as needing fsync */
VfdCache[file].fdstate |= FD_DIRTY;
+ } else
+ VfdCache[file].seekPos = FileUnknownPos;
return returnCode;
}
@@ -840,10 +845,26 @@ FileSeek(File file, long offset, int whence)
default:
elog(ERROR, "FileSeek: invalid whence: %d", whence);
break;
- }
}
- else
+ } else
+ switch (whence) {
+ case SEEK_SET:
+ if (offset < 0)
+ elog(ERROR, "FileSeek: invalid offset: %ld", offset);
+ if (VfdCache[file].seekPos != offset)
+ VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
+ break;
+ case SEEK_CUR:
+ if ((offset != 0) || (VfdCache[file].seekPos == FileUnknownPos));
VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
+ break;
+ case SEEK_END:
+ VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
+ break;
+ default:
+ elog(ERROR, "FileSeek: invalid whence: %d", whence);
+ break;
+ }
return VfdCache[file].seekPos;
}
--
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