Rick Delaney wrote:
> Jan Wieck wrote:
> >
> > Rick Delaney wrote:
> >
> > >
> > Be aware that 6.5.* might be unable to deal with the resulting size of
> > the rewrite rule. And I'm not sure that I'll get TOAST ready for 7.0 to
> > handle it.
>
> I'd have to take a good look at all the expressions again to know if I could do
> this but I think I probably can. Only, with what I've started on I'm already
> getting "rule plan string too big" errors. (What I've started on is just one
> view that doesn't have all the expressions in it yet).
That's what I meant with "might be unable...". You talked about a 50 column view with complicated expressions,
andthat's surely too large for the current implementation.
> So I will just get the same thing with nested views, no? That is how I
> understand the "The Postgres Rule System" section of the manual and Tom Lane's
> answer to my post.
As the author of "The Postgres Rule System" I say yes, except that it requires some recursions in the rewriter.
Thus,it will take a little longer to rewrite, but that's a constant time per query, not depending on the amount
ofdata you're selecting. So if you're happy with the response times for your test queries, it's not the rewriter any
moreif you get response time problems later.
>
> If I could structure things as
>
> subset_1_n -> subset_1_n-1 -> ... -> subset_1_2 -> subset_1_1
> subset_2_n -> subset_2_n-1 -> ... -> subset_2_2 -> subset_2_1
> :
> :
> subset_m_n -> subset_m_n-1 -> ... -> subset_m_2 -> subset_m_1
>
> final -> join subset_1_n, subset_2_n, ..., subset_m_n
>
> where each view subset_i_n has a usably-sized rule plan string then could I get
> this thing working?
As said, there is a limit of 10 recursions for the rewriter actually hardcoded in rewriteHandler.c (line 1466).
Raisethat value if you get "infinite loop" errors.
> This will be primarily INSERT/UPDATE a row and then SELECT the view of that row.
> Am I right that a trigger would make more sense in this case then?
If you only insert one row, then select that one row, the cascaded view setup is best IMHO. The trigger solution
wouldonly be better, if you seldom do INSERT/UPDATE, but often SELECT and maybe SELECT many rows.
Jan
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#========================================= wieck@debis.com (Jan Wieck) #
