Subject Re: sweep rule of thumb timings
Author csswa
--- In ib-support@y..., "Ann W. Harrison" <aharrison@i...> wrote:

> you disable garbage collection in your backup. One reason for long
> backups with garbage collection enabled is an index with a large
> number of duplicate values. The number depends on the page size
> and the page buffer count, but oddly not on the key size. If you
> have such an index, you might consider adding a more selective
> value (e.g. the primary key) to the index to reduce garbage
> time.

Aha, now this is interesting. Yes, I just checked the selectivity of
my test-generated data and it is very low for the three main fields.
Only 146 distinct NAME fields, 106 for PHONE, and 69 for COUNTRY.
There are single-field indexes on NAME and COUNTRY in addition to
integer PK index. Across a million-record db that has to be costly
in some way.

I've read the excellent generational architecture overview here:
(and original here, sans Jim's preface),1410,25260,00.html

but I don't get how indexes factor into sweeping?? We are just
talking about time to locate each record??

I just dropped those two indexes, ran the gfix sweep, and it took the
same time as before, about 15 min on the abovementioned db :-(

Andrew Ferguson

> Regards,
> Ann
> We have answers.
> Question for anglophones. When I was growing up, the three
words "trash",
> "garbage", and "rubbish" had different meanings. Now, they are
> (except by me) used interchangeably, except in a metaphorical sense.
> "Trash talk", "garbage mouth", and "utter rubbish" convey quite
> meanings, but trash, garbage, and rubbish are interchangeable.
> To me, trash is paper and other dry combustible home detritus.
> is food waste, collected by the pig man, if he got there before the
> skunks. Rubbish is non-combustible. Consider a can of tomatoes
> past its expiry date. The tomatoes are garbage, the can is rubbish,
> and the label is trash. These days, I guess, the metaphorical
> are more significant than the real ones and the whole thing is
> to be chucked in the garbage can and collected by the trash man.
> Here endth the lecture.