What is the best practice these days for using registered
queries? I was under the impression that the pattern should be:
1) Create your query:
$query := cts:and-query ((blah blah blah))
2) Register it and make a registered query from it in one step:
$reg-query := cts:resistered-query (cts:register ($query), "unfiltered")
3) Use it in a search:
cts:search (fn:doc(), $reg-query)
The theory being that if the cts:query described by $query is
already registered, then the registration is essentially a no-op
and you'll get back the same ID. And doing this every time insures
that if the registered query has been evicted for some reason then
it's re-registered and all is well.
It's a nice theory but seems to be based on the assumption that
creating a cts:query object is very cheap. Unfortunately, I'm finding
that this is often not the case, especially when there are lots of
documents in the database. I have a test case where performing Step 2
above on a moderately complicated query takes roughly 200ms every time.
Others take even longer and all seem to be proportional to database size.
But running Step 3 with cts:registered-query(<regid>) is very, very
fast (~0ms). Re-creating the query for re-registering every time is
destroying the benefit of using a registered query.
I can obviously save the registration ID obtained from calling
cts:register and then make a cts:registered-query each time, but then
I'm not protected from the query becoming unregistered. And there is
no lightweight way to test if an ID is still registered. The only way
I know to make this robust is to put a loop and try/catch around the
code that does the search. But that requires passing along enough
context to re-construct and re-register the queries (there can be
dozens of them in this case). This is obviously a lot harder than
building the complex query in one module and then passing it along
to the search code somewhere else.
What's the generally accepted best usage pattern for registered
queries? And is it my imagination or has the cost of running queries
been moving from query evaluation into query construction?
Thanks.
---
Ron Hitchens {mailto:[email protected]} Ronsoft Technologies
+44 7879 358 212 (voice) http://www.ronsoft.com
+1 707 924 3878 (fax) Bit Twiddling At Its Finest
"No amount of belief establishes any fact." -Unknown
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