I have 2 xml docs, each about 1GB and about 2 mil fragments ("rows")
each ... in fact the elements are called "rows".
Each "row" element is about 500 bytes. But I dont yet have a better
way to fragment them.
( Yes Its been suggested to split these to seperate docs and I may
experiment with that. )
Here's a case where I've found ML refuses to optimize xpaths.
First off, this expression takes about 5 seconds, which I find a little
slow ... it returns 8 rows.
declare variable $id := '2483417';
for $r in doc("/RxNorm/rxnsat.xml")/rxnsat/row[RXAUI eq $id]
return $r
Now to complicate things I actually need $id from a previous query so
the real query is like
declare variable $id := '2483417';
declare variable $c := doc("/RxNorm/rxnconso.xml")/rxnconso/row[RXAUI eq
$id];
declare variable $id2 as xs:string := $c/RXAUI/string();
for $r in doc("/RxNorm/rxnsat.xml")/rxnsat/row[RXAUI eq $id2]
return $r
This takes about 1 minute ! .. Checking the profile I find the
expression row[ RXAUI eq $id] is evaluated a million times ...
indicating its not doing indexing.
I've tried all sorts of combinations of these like
doc("/RxNorm/rxnsat.xml")/rxnsat/row[xs:string(RXAUI) eq $id2]
doc("/RxNorm/rxnsat.xml")/rxnsat/row[RXAUI eq $c/RXAUI]
doc("/RxNorm/rxnsat.xml")/rxnsat/row/RXAUI[. eq $id2]/ancestor::row
All to the same avail ... no indexing !
But of course this brings things back to speed
---------
for $r in cts:search(doc("/RxNorm/rxnsat.xml")/rxnsat/row,
cts:element-query( xs:QName("RXAUI") , $id2 ))
return $r
------------
Still takes too long (about 5 sec) ... but its back to realtime atleast.
I'm experimenting now with fields ...
But I find it strange that I cant the xpath expression to use the
indexes in one case but it does in another that seems almost identical
to me.
This expression
declare variable $id2 as xs:string := $c/RXAUI/string();
should tell the system that $id2 is a single string so why wont it use
it in xpath based index queries ?
----------------------------------------
David A. Lee
Senior Principal Software Engineer
Epocrates, Inc.
[email protected] <mailto:[email protected]>
812-482-5224
_______________________________________________
General mailing list
[email protected]
http://xqzone.com/mailman/listinfo/general
