Re: How does TOAST compare to other databases' mechanisms?

At 20:42 13/10/00 -0400, Tom Lane wrote:
>Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
>> At 10:12 9/10/00 -0400, Tom Lane wrote:
>>> Someone should work on adding an
>>> ALTER command to change it in a more user-friendly fashion.
>
>> If I wanted to do this, how long do you think it would take (given that I
>> have not done anything similar so far)?
>
>Hard to say. Do you know anything about yacc grammars?

I added a 'get statistics' statement to plpgsql a while back, but I don't
think it made it into CVS. So yes, I have at least seen yacc before.

> You'd have
>to add a production to gram.y to define the syntax, probably extend
>the existing AlterStmt data structure (which implies touching support
>code in backend/nodes), and then add some execution code that checks
>for a valid command (ie, that the data column type is toastable)

This sounds fine, but begs the question: if there is TOASTed data in the
table and the column is set to 'not TOASTed', will TOAST cope? And vice verca?

>finally applies the pg_attribute change.

This sounds cloneable.

>All told it might be a couple
>hundred lines of new or changed code. Pretty much all of this could
>be done by cribbing from existing code (ie. programming-by-example)
>which is a good thing because there's not much documentation.

So it might be worh documenting, too...

>Someone who already knew what they were doing could do it in an hour
>or two. Not sure how much learning time you'd need to figure on top
>of that. But if you're interested in learning to hack the backend,
>this seems like a pretty reasonable first project.

Sounds good to me; if I can't get it into the beta, then it's no real
problem I guess. Main constraint will be my real work, which is fairly
intense at the moment.

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