At 06:44 PM 25/05/2008, you wrote:

>Hi,
>
>I have INDEX performance problem with FB superserver V2.1 on WinXP.
>
>I'm using the IBObjects ordering-change mechenism.
>The foward INDEX ordering is fast, but backward INDEX ordering is slow.

The optional backward index ordering requires a corresponding DESC index.

>This problem suddenly happened between 160 and 170 VARCHAR size of UTF8
>Charcter set.
>I get the following result in backward INDEX ordering test case.
>
>Size: min - max
>VARCHAR(100): 0.51 - 0.60(s)
>VARCHAR(150): 0.78 - 0.84(s)
>VARCHAR(160): 0.79 - 0.86(s)
>VARCHAR(170): 3.51 - 3.59(s)
>VARCHAR(200): 4.30 - 5.51(s)
>VARCHAR(250): 6.25 - 6.44(s)
>
>Is this a performance limit of V2.1?
>Please any suggestion.
>
>
>Firebird.conf settings:
>
>- DefaultDbCachePages = 16384
>- TempBlockSize = 3200000 (or 6400000)
>
>Test sequences:
>
>1. Creation table and index
>
>CREATE TABLE Test (
>I INTEGER NOT NULL
>, V VARCHAR(nnn) CHARACTER SET UTF8
>, CONSTRAINT TS1PK PRIMARY KEY (I));
>
>CREATE INDEX IDX01 ON Test(I);

also
CREATE DESC INDEX IDX02 ON Test(I);

There has been no change, by the way. Firebird never could use an ASC index to perform a DESC sort - and it still can't. Likewise, in IBO, providing both ascending and descending sort orders to your ordering items is pointless if only the ASC index exists.

./heLen