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.

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);

2. Insert 100,000 records

INSERT INTO Test(I,V) VALUES(:I,:V);

3. Change ordering :SQL as bellow.

- Forward

SELECT * FROM Test
ORDER BY V ASC
PLAN (Test ORDER IDX01)

- Backward

SELECT * FROM Test
ORDER BY V DESC
PLAN SORT ((Test NATURAL))

　
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Regards,
Minoru