Re: Index compression vs. table compression

Howard J. Rogers wrote:
> I am indeed sorry, that despite my very clearly having said that I
did
> NOT say 'lookup tables' in the sentence which Tom Kyte has discussed
at
> length, you won't accept the point. Daniel and Richard not accepting
it,
> I can understand, since they have agendas going back years. You not
> accepting it, I don't understand. Read the words I wrote. Don't add
any.
> And then deduce the meaning from them. This is usually how language
works.
<SNIP>
> In my brief discussion with Jonathan, however, I said something else
> entirely (namely, that small tables would be likely read via a FTS,
even
> with single key lookups). I'm indeed equally sorry if that basic
> distinction escapes you. And I went on, in another post, to *prove*
that
> can be the case.

Sorry for being pedantic, but you really are missing my point.

1. You said (way back): how is the optimiser likely to read small, useful, lookup tables?.. er, via a FTS, probably, if they are genuinely small.

Note:
- YOU introduced the term "lookup table" at this point. Agreed? - YOU said that the optimiser is likely to use an FTS on a lookup table. Agreed?

2) JL rsponded: Not if they're being used for doing lookups, I hope.

Note:
- JL's "they" refers to the "lookup tables" YOU were talking about in (1). Agreed?
- JL is asserting that an FTS would hopefully not be used for a lookup table. Agreed?

3) You replied: Why? A small table is always likely to be read via a FTS using CBO. Even for a single key lookup...

Note:
- Your "Why?" is addressed to JL's assertion about LOOKUP TABLES. Agreed?
- You are doubting JL's assertion that the optimizer would use a FTS on a lookup table. Agreed?

You THEN start to atempt to justify your argument by talking about something that is NOT NECESSARY a lookup table (a "small table"). But a resonable jury might assume that someone reading this (such as TK) might assume that by "small table...single key lookup" you were not intending to change the subject, but were in fact still talking about LOOKUP TABLES, as you had been to start with.

Having (deliberately or not?) confused everyone by changing the subject under discussion without explicitly saying that was your intention, you then blame everyone else for twisting your words.

Do you accept that the original statement you made (my quote (1) above) was wrong, or don't you? The fact that you proved yourself right about something else altogether later on (something no one was claiming otherwise) is neither here nor there!

> And my subsequent post to Tom,
> *before* he started talking about what he assumed I'd meant,
explained
> in totally unambiguous terms what *I* meant by 'single key lookups':
a
> search of EMP for an EMPNO. Would you call EMP a lookup table?
>
> No, I didn't think so.

Well, a real EMP table would have EMPNO as primary key, so a search of EMP for an EMPNO would behave exactly like the lookup table search, i.e. use the index. It is only in your contrived version of EMP with no primary key, and where every EMPNO appears 32 times, that an FTS may be more appropriate.

I hate to say it, but you seem to be suffering from Burleson Syndrome ;) Received on Mon Jan 24 2005 - 04:51:16 CST