Goo'day Mark,
At 23:50 20/10/05 -0400, you wrote:
I'm wondering if a UD or UV system behaves similarly to a D3 problem I see.
File contains 6,000,000 records. First field is DATE and 2nd field is CUST.
Both are INDEXed.
SELECT FILE WITH DATE = "10.18"
quickly returns 11,000 items
CLEARSELECT
SELECT FILE WITH CUST = "12345"
quickly returns 180,000 items
CLEARSELECT
SELECT FILE WITH DATE = "10.18" AND CUST = "12345"
takes forever as if the indexes aren't there.
AFAIK, all MV variants only use the first iindex.
If you try to use 2 indices, none are used..... Must be documented.....
somewhere....
The old story applies: Use successive SELECTs to get the benefit of
multiple indices....
I don't know if the double test in the SELECT statement ignores the INDEX on
either (or the first) or is encumbered by taking the 11,000 quick DATE items
and then hashingly goes through them looking for CUST.
If I try
SELECT FILE WITH DATE = "10.18"
then
SELECT FILE WITH CUST = "12345"
it still takes longer than I would expect.
Is a double INDEX a strange animal. Does U2 support indexing virtual fields,
ie DATE.CUST? I don't think D3 can.
Why not? The index is built on a DICT item..... Wasn't there a discussion
somewhere in the past week over indexing null items and the suggestion was
to non-null them by adding something else to the key?
Thanks in advance.
Mark Johnson
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Regards,
Bruce Nichol
Talon Computer Services
ALBURY NSW 2640
Australia
http://www.taloncs.com.au
Tel: +61 (0)411149636
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If it ain't broke, fix it till it is!
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