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

[Christian Grün]

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]
>
> ----------------------------------------
>
>
>
> 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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