Hi,
And most importantly thanks for this contribution, I think
it's a very nice one and can easily replace any temp tables
created on disk. I'll now go and convert my app to use it.
the primary idea was more a toy I/O driver than the really useful
addition to harbour. Linux users can reach a similar effect by storing
files at /dev/shm. Disk buffers also makes a disk to be a little similar
(by speed) to memory. I still wanted to test disk overhead on local
drives, so, I've wrote this I/O driver. Test (source code is presented
below) execution times are:
Mem I/O:
DBAPPEND 13203
INDEX 8375
DBEVAL 6890
File I/O:
DBAPPEND 24563
INDEX 9266
DBEVAL 11484
But now I'm thinking about including this I/O driver into one of the
projects. We have about a 1 million records in database and report
generation is too slow in network environment (in local environment
speed is acceptable). I'm thinking about copying the whole remote file
(well, about 100MB...) to memory file system, and generating report from
memory.
Regards,
Mindaugas
REQUEST HB_IODMEM
#define COUNT 2000000
PROC main()
LOCAL nI, nJ, nT
FIELD F1, F2
? "Mem I/O:"
DBCREATE("mem:test", {{"F1", "C", 64, 0}, {"F2", "N", 9, 0}},, .T.,
"memtest")
nT := HB_MILLISECONDS()
FOR nI := 1 TO COUNT
DBAPPEND()
F2 := HB_RANDOM() * 1000000
F1 := "Blah, blah, blah..." + STR(RECNO()) + " " + STR(F2)
NEXT
? " DBAPPEND ", HB_MILLISECONDS() - nT
nT := HB_MILLISECONDS()
INDEX ON F2 TAG F2
? " INDEX ", HB_MILLISECONDS() - nT
nT := HB_MILLISECONDS()
nJ := 0
DBEVAL({|| nJ += F2})
? " DBEVAL ", HB_MILLISECONDS() - nT
DBCLOSEALL()
DBDROP("mem:test")
? "File I/O:"
DBCREATE("test", {{"F1", "C", 64, 0}, {"F2", "N", 9, 0}},, .T.,
"memtest")
nT := HB_MILLISECONDS()
FOR nI := 1 TO COUNT
DBAPPEND()
F2 := HB_RANDOM() * 1000000
F1 := "Blah, blah, blah..." + STR(RECNO()) + " " + STR(F2)
NEXT
? " DBAPPEND ", HB_MILLISECONDS() - nT
nT := HB_MILLISECONDS()
INDEX ON F2 TAG F2
? " INDEX ", HB_MILLISECONDS() - nT
nT := HB_MILLISECONDS()
nJ := 0
DBEVAL({|| nJ += F2})
? " DBEVAL ", HB_MILLISECONDS() - nT
DBCLOSEALL()
DBDROP("test")
RETURN
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