Rdrg109 created this task.
Rdrg109 added a project: Wikidata-Query-Service.
Restricted Application added a subscriber: Aklapper.
TASK DESCRIPTION
**The context**
Before describing the issue, please let me present some context.
Query 1: This query returns the highest point of Earth and Mars. I executed
it and it returned 4 results in 110ms, also, all the returned values were
unique. To me, this is expected behavior.
SELECT ?value {
VALUES ?item {wd:Q2 wd:Q111}.
?item wdt:P610 ?value.
}
Query 2: This query returns the distinct values of highest point of the item
Earth. I executed it and it returned 3 results in 123ms. To me, this is
expected behavior.
SELECT DISTINCT ?value {
VALUES ?item {wd:Q2}.
?item wdt:P610 ?value.
}
Query: 3: This query returns the distinct values of highest point of Earth
and Mars. I executed it and it returned 11158 results in 197ms. To me, this is
**NOT** expected behavior.
SELECT DISTINCT ?value {
VALUES ?item {wd:Q2 wd:Q111}.
?item wdt:P610 ?value.
}
Query 4: This query does the same of Query 3, but it is enclosed in a named
subquery. I executed it and it returned 4 results in 133ms. To me, this is
expected behavior.
SELECT *
WITH {
SELECT DISTINCT ?value {
VALUES ?item {wd:Q2 wd:Q111}.
?item wdt:P610 ?value.
}
} AS %0
{
INCLUDE %0.
}
I think Query 3 has a problem. I've described my reasoning below.
**Steps to replicate the issue**
1. Execute the following query (previously called Query 3) in WDQS.
SELECT DISTINCT ?value {
VALUES ?item {wd:Q2 wd:Q111}.
?item wdt:P610 ?value.
}
The query query returned 11158 (as of the time of this writing), even though
the distinct values for highest point (P610
<https://www.wikidata.org/wiki/Property:P610>) of Earth (Q2) and Mars (Q111)
are only 4, as shown by Query 1 and Query 4.
**What should have happened instead?**:
The query should have returned 4 items, since the `DISTINCT` values for
"Earth" (Q2) and "Mars" (Q111) are only 4 (this can be proved by executing
Query 1 or Query 4).
**Additional information**
I think the bug is when using `DISTINCT` with `VALUES`.
The following query gets the value of parent taxon (P171
<https://www.wikidata.org/wiki/Property:P171>) of hippopotamus (Q34505) and
tiger (Q19939). I executed it and it returned 2 results in 296ms.
SELECT ?value {
VALUES ?item {wd:Q34505 wd:Q19939}
?item wdt:P171 ?value.
}
I executed the query with `DISTINCT` (see below) and it timed out.
SELECT DISTINCT ?value {
VALUES ?item {wd:Q34505 wd:Q19939}
?item wdt:P171 ?value.
}
**Software version**
WDQS as of the time of this writing.
**Other information**
Browser: Mozilla Firefox 106.0.1
TASK DETAIL
https://phabricator.wikimedia.org/T321855
EMAIL PREFERENCES
https://phabricator.wikimedia.org/settings/panel/emailpreferences/
To: Rdrg109
Cc: Aklapper, Rdrg109, AWesterinen, MPhamWMF, CBogen, Namenlos314, Gq86,
Lucas_Werkmeister_WMDE, EBjune, merbst, Jonas, Xmlizer, jkroll, Wikidata-bugs,
Jdouglas, aude, Tobias1984, Manybubbles
_______________________________________________
Wikidata-bugs mailing list -- wikidata-bugs@lists.wikimedia.org
To unsubscribe send an email to wikidata-bugs-le...@lists.wikimedia.org
