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"David Chan" — — source: Informix-list mailing list archive (1991-1998)
>1. Is there a way to place a table's index in a dbspace other than the
> dbspace containing the table, presumably on a different disk?
You can do this in v7. You can also spread an index over several
dbspaces based on a range of values or a hash value. However I would
still want to store a mix of index and data on each disk.
>2. Do Informix's indexes tend to be "deep" or "wide"?
Depends on the size of fields in the index. You will probably find that
an index page is only 2/3 full because of node splits.
>Your 5 index reads per data read seems high to me, unless the table is
>REALLY big, thus making even "wide" indexes into "deep" ones as well.
>Even with deep indexes, wouldn't the first few levels stay in the cache,
>reducing the physical reads to only the lower levels for subsequent
index
>searches?
Yes 5 was a bit high. The first 2-3 levels would be cached.
David W Chan
Objective Research Ltd
dwc@cix.compulink.co.uk
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