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Direct XML interfaces to optimizer and even executor?

From: Gunther Schadow <gunther(at)aurora(dot)regenstrief(dot)org>
To: pgsql-interfaces <pgsql-interfaces(at)postgresql(dot)org>
Subject: Direct XML interfaces to optimizer and even executor?
Date: 2002-05-30 20:28:54
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Lists: pgsql-interfaces

I posted this earlier to general but got zero response. So, I'm
directing it to a more specific group.

I'm wondering about alternative interfaces to a PostgreSQL data base
backend. Interfaces other than the SQL loanguage. I know one can map
many things to SQL, but let me think outside the box for just a

- Sending a parse tree in XML for processing by the optimizer.
    This circumvents the SQL language and avoids the kinds of
    syntactic ideosyncrasies of SQL (e.g., where you put commas.)
    This is fairly trivial, but of course the question is, would
    it be worth it?

- Sending an execution plan in XML directly to the executor.
    This now circumvents the SQL parser and optimizer. I know this
    is in a way against the relational doxology and I don't take that
    light-heartedly. However, isn't it true that most optimizers
    cannot deal very well with more than 6 joins? I may be wrong,
    but I find myself spending quite a bit of time fighting with the
    Oracle or PostgreSQL optimizer to convince it to choose the plan
    that I want. There is so much magic to it with hints and the
    way you write SQL (where in relational theory the expressions are
    equivalent, they make huge difference in what plan is being
    generated.) So, it appears to me almost easier to just send a
    plan directly and have the system execute that plan.

- These direct interfaces could be a nice way to experiment with
    new strategies without having to implement it on all three
    layers (SQL language, optimizer, and executor.)

You noticed I sneaked in XML as the interface, and that would be
neat because with XSLT it's so easy to manipulate. But I'm also
thinking about a Prolog binding or constraint logic programming
binding, that might be better optimizeable if it goes through a
more direct path than SQL.

I'd appreciate comments on this, even if you think it is a
worthless idea (of course would be grateful about hearing why.)


Gunther Schadow, M.D., Ph.D.                    gschadow(at)regenstrief(dot)org
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine

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Subject: Re: Direct XML interfaces to optimizer and even executor?
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