| Re: Dataminer: faster way to get all records in a IDLdbRecordset table? [message #36459 is a reply to message #36446] |
Wed, 17 September 2003 09:03   |
Dick Jackson
Messages: 347
Registered: August 1998
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Senior Member |
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Hi Tim,
"Tim Williams" <timothy.williams@nvl.army.mil> wrote in message
news:faf44c99.0309170738.ae75526@posting.google.com...
> I want to put the records in a database table into an IDL table
> widget. For fairly large tables, (> ~1500 rows), it's fairly slow and
> I get "Not responding" in the Task Manager for awhile while I'm
> getting each record. Here's what I'm doing now:
>
> ors=obj_new('IDLdbRecordset', table=tablename)
> status=ors->moveCursor(/first)
> if status eq 1 then begin
> rec=ors->getRecord()
> status=ors->moveCursor(/next)
> while (status eq 1) do begin
> rec=[rec, ors->getRecord()]
> status=ors->moveCursor(/next)
> end while
> endif
>
> Is there a faster way to get all of the records?
With that number of records, I think a lot of time may be in the
innocent-looking array concatenation:
rec=[rec, ors->getRecord()]
At the end, you're taking an array of 1498 records, creating a *new*
array with 1499 records and throwing out the old one. Lots of extra
memory copying here. My faster way is below (this would go within your
'if status eq 1' block, and you'll have to rework the variable names, of
course):
=====
;; Count how many records
nRecords = 0L
WHILE status NE 0 DO BEGIN
nRecords = nRecords+1
status = objRS -> MoveCursor(/Next)
ENDWHILE
;; Get structure from first record, replicate it
status = objRS -> MoveCursor(/First)
aRecord = objRS -> GetRecord()
result = Replicate(aRecord, nRecords)
FOR recordI=1, nRecords-1 DO IF status NE 0 THEN BEGIN
status = objRS -> MoveCursor(/Next)
IF status EQ 0 THEN $ ; Fewer records than when
counted above
result = result[0:recordI-1] $
ELSE result[recordI] = objRS -> GetRecord()
ENDIF
=====
Hope this helps!
Cheers,
--
-Dick
Dick Jackson / dick@d-jackson.com
D-Jackson Software Consulting / http://www.d-jackson.com
Calgary, Alberta, Canada / +1-403-242-7398 / Fax: 241-7392
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