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Commita194574

Browse files
committed
> 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
1 parent434adee commita194574

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1 file changed

+26
-5
lines changed
  • src/backend/storage/file

1 file changed

+26
-5
lines changed

‎src/backend/storage/file/fd.c

Lines changed: 26 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.59 2000/06/02 15:57:24 momjian Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/storage/file/fd.c,v 1.60 2000/06/14 03:19:24 momjian Exp $
1111
*
1212
* NOTES:
1313
*
@@ -95,6 +95,8 @@
9595

9696
#defineFileIsNotOpen(file) (VfdCache[file].fd == VFD_CLOSED)
9797

98+
#defineFileUnknownPos (-1)
99+
98100
typedefstructvfd
99101
{
100102
signed shortfd;/* current FD, or VFD_CLOSED if none */
@@ -790,6 +792,8 @@ FileRead(File file, char *buffer, int amount)
790792
returnCode=read(VfdCache[file].fd,buffer,amount);
791793
if (returnCode>0)
792794
VfdCache[file].seekPos+=returnCode;
795+
else
796+
VfdCache[file].seekPos=FileUnknownPos;
793797

794798
returnreturnCode;
795799
}
@@ -806,11 +810,12 @@ FileWrite(File file, char *buffer, int amount)
806810

807811
FileAccess(file);
808812
returnCode=write(VfdCache[file].fd,buffer,amount);
809-
if (returnCode>0)
813+
if (returnCode>0) {
810814
VfdCache[file].seekPos+=returnCode;
811-
812815
/* mark the file as needing fsync */
813816
VfdCache[file].fdstate |=FD_DIRTY;
817+
}else
818+
VfdCache[file].seekPos=FileUnknownPos;
814819

815820
returnreturnCode;
816821
}
@@ -840,10 +845,26 @@ FileSeek(File file, long offset, int whence)
840845
default:
841846
elog(ERROR,"FileSeek: invalid whence: %d",whence);
842847
break;
843-
}
844848
}
845-
else
849+
}else
850+
switch (whence) {
851+
caseSEEK_SET:
852+
if (offset<0)
853+
elog(ERROR,"FileSeek: invalid offset: %ld",offset);
854+
if (VfdCache[file].seekPos!=offset)
855+
VfdCache[file].seekPos=lseek(VfdCache[file].fd,offset,whence);
856+
break;
857+
caseSEEK_CUR:
858+
if ((offset!=0)|| (VfdCache[file].seekPos==FileUnknownPos));
846859
VfdCache[file].seekPos=lseek(VfdCache[file].fd,offset,whence);
860+
break;
861+
caseSEEK_END:
862+
VfdCache[file].seekPos=lseek(VfdCache[file].fd,offset,whence);
863+
break;
864+
default:
865+
elog(ERROR,"FileSeek: invalid whence: %d",whence);
866+
break;
867+
}
847868
returnVfdCache[file].seekPos;
848869
}
849870

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