Re: [basex-talk] some eq versus =

[Christian Grün]

Hi Leo,

I came across this question because I needed to know whether there are city
> elements twice in the file. For that I wrote version 2 and the result was
> wrong. Then I wrote version 1 with
> … satisfies . => deep-equal($city)
> that gave the correct answer. I noticed that I do not fully understand the
> cast behavior of the = operator…
>

Thanks. deep-equal() is probably what you want. If you use generalized
comparisons (=, !=, etc.), or if you use “data(.)” or “string(.)”, the
descendant text nodes of the referenced node will be concatenated and
returned as single string. As a result, queries like the following one…

  X = X

…will return “true” because the atomized value of both operands is“X”.

Sibling node traversals are often slow, as the same nodes are repatedly
processed.

  for $city-group in //city
  group by $string := serialize($city-group)
  where count($city-group) > 1
  return head($city-group)

With the latest BaseX 11 snapshot and the upcoming XQuery 4 features, it
could be:

  for value $v in map:build(//city, serialize#1)
  where count($v) > 1
  return head($v)

Hope this helps,
Christian

Re: [basex-talk] some eq versus =

[Leo Studer]

Hi Christian Thanks for your answer. I came across this question because I needed to know whether there are city elements twice in the file. For that I wrote version 2 and the result was wrong. Then I wrote version 1 with … satisfies . => deep-equal($city)that gave the correct answer. I noticed that I do not fully understand the cast behavior of the = operator…Blessings,LeoSent from my dish washer On 9 Apr 2024, at 11:28, Christian Grün  wrote:Hi Leo,Yes, they are equivalent. Version 2 is a bit faster because "." will only need to be atomized once.We’ll examine if BaseX can automatically rewrite version 1 to version 2.Best,ChristianOn Mon, Apr 8, 2024 at 11:59 PM Leo Studer  wrote:Helloare the following queries equivalent?1. //city[some $city in following::city satisfies string(.) eq string($city)]2. //city[. = following::city ]Thanks in advance,Leo

Re: [basex-talk] some eq versus =

[Christian Grün]

Hi Leo,

Yes, they are equivalent. Version 2 is a bit faster because "." will only
need to be atomized once.

We’ll examine if BaseX can automatically rewrite version 1 to version 2.

Best,
Christian


On Mon, Apr 8, 2024 at 11:59 PM Leo Studer  wrote:

> Hello
>
> are the following queries equivalent?
>
> 1. //*city*[*some* *$city* *in* following::*city* *satisfies* *string*(.)
> eq *string*(*$city*)]
>
> 2. //*city*[. = following::*city* ]
>
>
>
> Thanks in advance,
> Leo
>
>
>

Re: [basex-talk] some eq versus =

[Martin Honnen]

On 08/04/2024 23:58, Leo Studer wrote:

Hello

are the following queries equivalent?

1. //*city*[*some* *$city* *in* following::*city* *satisfies*
/string/(.) eq /string/(*$city*)]


2. //*city*[.=following::*city*]




More or less, I would say, depending on whether there is schema-aware
processing done or not where perhaps . = following::city might not do
string comparison.