Re: [basex-talk] Spectactularly slow performance with db:open vs. db:text

Hi Constantine,

for $a in (db:open('DB1')/item/order-id) return if (db:open('DB2')//order-id[. = $a]) then $a else ()

Do some of the order-id elements contain descendant elements?

db:open('DB1')/item/order-id[*]

If yes, the following query might be faster:

for $a in (db:open('DB1')/item/order-id) return if (db:open('DB2')//order-id[text() = $a]) then $a else ()

Here is another way to rewrite the query:

for $a in (db:open('DB1')/item/order-id) where db:open('DB2')//order-id[text() = $a] return $a

Note that the optimized query uses db:open-pre to access DB2. When I re-write the query myself to use the TEXT index then performance is excellent. But why such a difference?

Query 2 [returns in 0.3 second]

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for $a in (db:open('DB1')/item/order-id)

return

if (db:text('DB2', $a)/parent::order-id) then

$a

else

()

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