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Filter optimization |
Wed, Feb 15 2006 2:03 PM | Permanent Link |
Kai Peters | Hi ~ just tried everything I could think of and could not get it to work: Is there no way to set a fully optimized filter in the scenario below? Field: Last_Name (String) contains last names in proper case, upper case & lower case, i.e. SMITH Smith SMitH I'd like to set a filter like 'LAST_NAME =3D '''SMITH''' and have all three records found with OptimizeLevel =3D foFull I thought that setting the index on last_name to be case-insensitive would achieve that - but apparently not - it always yields foNone Setting a filter to 'Upper(last_name) =3D 'SMITH' also loses all optimization so is there anything I can do? TIA, Kai |
Wed, Feb 15 2006 2:27 PM | Permanent Link |
"Ralf Mimoun" | Kai Peters wrote:
.... > I'd like to set a filter like 'LAST_NAME = '''SMITH''' and have all > three records found with OptimizeLevel = foFull 1) Define a case insensitve index for LAST_NAME 2) try UPPER(LAST_NAME)=UPPER('SMITH') as filter Without that UPPER(), DBISAM will do a case sensitive filtering, no matter what index exists. And that's a very good thing, because the structure of some herlp constructs like indexes should never change the result of a SELECT statement or a filter (except the order in a SELECT statement if no ORDER BY is used - in that case, order is undefined and you can't rely on getting exactly what you want). Ralf |
Wed, Feb 15 2006 2:27 PM | Permanent Link |
Roy Lambert NLH Associates Team Elevate | Kai
Everyone seems to fall into this trap. Use 'Upper(last_name) =Upper( 'SMITH') You need both so DBISAM understands - its a bit thick Roy Lambert - ducking the blow from Tim |
Thu, Feb 16 2006 4:49 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Roy,
<< You need both so DBISAM understands - its a bit thick Roy Lambert - ducking the blow from Tim >> I agree that it's thick, compared to us. If I could transfer even a small percentage of the "smarts" in humans to DBISAM (or any product, for that matter), I'd be a rich man. -- Tim Young Elevate Software www.elevatesoft.com |
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