# From 30ms to 7000ms when asking for edgeAttributeProperty?

**URL:** <https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186>\
**Category:** Support\
**Created:** [August 7, 2021, 12:39pm UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186 "2021-08-07T12:39:38Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![lapidus](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/lapidus/32/1076_2.png) [@lapidus](https://community.stardog.com/u/lapidus)\
**Post date:** [August 7, 2021, 12:39pm UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/1 "2021-08-07T12:39:39Z")

</div>

I am testing some basic queries (on an instance with ~10m triples) around edge attributes and noticed a very large difference between including a wildcard ?edgeAttributeProperty or not:

A) \<50 ms

```auto
SELECT ?p ?o ?edgeAttributeObject {
<< :angola ?p ?o >> ?edgeAttributeProperty ?edgeAttributeObject
}

```

B) \> 7000 ms

```auto
SELECT ?p ?o ?edgeAttributeProperty ?edgeAttributeObject {
<< :angola ?p ?o >> ?edgeAttributeProperty ?edgeAttributeObject
}

```

Can I speed this up somehow? (I.e. shouldn't the engine somehow be able to limit the scope of search to the triple and its related edge attributes? It seems to search unnecessarily wide?)

Here's the sample data for the query:

```auto
INSERT DATA {
<< :angola :independence_year 1961 >> :source :wikipedia, :dbpedia; :relatedEvent "Angolan War of Independence"
}

```

Thanks for any hints!

---

<div class="post-metadata">

**Author:** ![lapidus](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/lapidus/32/1076_2.png) [@lapidus](https://community.stardog.com/u/lapidus)\
**Post date:** [August 7, 2021, 12:45pm UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/2 "2021-08-07T12:45:16Z")

</div>

Update: If I include the complete triple statement, the same query is very fast again: (\<50ms)

```auto
SELECT ?p ?o ?edgeProperty ?edgePropertyObject {
<< :angola :independence_year 1961 >> ?edgeProperty ?edgePropertyObject
}

```

But still curious why the the wildcard becomes so expensive 🤔

Sidenote: Is there a way to reference a statement by an id/IRI? I.e. can I replace the triple part for an identifier?

```auto
SELECT ?p ?o ?edgeProperty ?edgePropertyObject {
**<< ID/IRI >>**?edgeProperty ?edgePropertyObject
}

```

---

<div class="post-metadata">

**Author:** ![jess](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/jess/32/10_2.png) [@jess](https://community.stardog.com/u/jess)\
**Post date:** [August 7, 2021, 6:56pm UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/3 "2021-08-07T18:56:53Z")

</div>

Hi Daniel,

Can you include the text format query plans from Stardog Studio or the output from the `stardog query explain` command?

Jess

---

<div class="post-metadata">

**Author:** ![lapidus](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/lapidus/32/1076_2.png) [@lapidus](https://community.stardog.com/u/lapidus)\
**Post date:** [August 8, 2021, 8:33am UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/4 "2021-08-08T08:33:32Z")

</div>

Thank you @jess,

Seems one scan differs between PSO and SPO? Could that account for the difference?

```auto
Slice(offset=0, limit=1000) [#1.0K]
`─ Projection(?p, ?o, ?edgeAttributeProperty, ?edgeAttributeObject) [#24.6M]
   `─ NestedLoopJoin(_) [#24.6M]
      +─ Bind(GetStatement(<https://graph.datastory.org/angola>, ?p, ?o, ?lqpfgaow) AS ?wxkfavur) [#1]
      │ `─ Scan[SPOC](<https://graph.datastory.org/angola>, ?p, ?o) [#1]
      `─ Scan[PSO](?wxkfavur, ?edgeAttributeProperty, ?edgeAttributeObject) [#24.6M]

```

```auto
Slice(offset=0, limit=1000) [#1.0K]
`─ Projection(?p, ?o, ?edgeAttributeObject) [#24.6M]
   `─ NestedLoopJoin(_) [#24.6M]
      +─ Bind(GetStatement(<https://graph.datastory.org/angola>, ?p, ?o, ?qyqnptfq) AS ?fqxnuhfl) [#1]
      │ `─ Scan[SPOC](<https://graph.datastory.org/angola>, ?p, ?o) [#1]
      `─ Scan[SPO](?fqxnuhfl, ?edgeAttributeProperty, ?edgeAttributeObject) [#24.6M]

```

---

<div class="post-metadata">

**Author:** ![pavel](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/pavel/32/18_2.png) [@pavel](https://community.stardog.com/u/pavel)\
**Post date:** [August 9, 2021, 7:17am UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/5 "2021-08-09T07:17:02Z")

</div>

Hi Daniel,

Yes, `PSO` vs `SPO` plays a role but the root cause is the join algorithm (nested loops). It can be very inefficient depending on the order in which operands produce inputs. It shouldn't be used in this case but there's a known issue PLAT-2502 which creates loop joins when the join variable is assigned in certain `BIND` expressions (in this case, `GetStatement`).

For now you'd need to use a longer form for this query instead of the `<<>>` shortcut:

```auto
SELECT ?p ?o ?edgeAttributeProperty ?edgeAttributeObject {
    :angola ?p ?o .
    bind(coalesce(getStatement(:angola, ?p, ?o), "") as ?statement)
    ?statement ?edgeAttributeProperty ?edgeAttributeObject .
}

```

Here I'm working around the problem by using an artificial `coalesce` call to tell the query engine that the `?statement` variable cannot have a `null` value so it can use faster join algorithms. This is a bit awkward and we should fix the issue soon (`GetStatement` shouldn't trigger errors and thus shouldn't return nulls in this case).

Let us know if this helps in the mean time,  
Pavel

PS. here's the plan you should see:

```auto
Slice(offset=0, limit=1000) [#1.0K]
`─ Projection(?p, ?o, ?edgeAttributeProperty, ?edgeAttributeObject) [#10K]
   `─ MergeJoin(?statement) [#10K]
      +─ Scan[SPO](?statement, ?edgeAttributeProperty, ?edgeAttributeObject) [#10K]
      `─ Sort(?statement) [#1]
         `─ Bind(COALESCE(GetStatement(:angola, ?p, ?o), "") AS ?statement) [#1]
            `─ Scan[SPOC](:angola, ?p, ?o) [#1]

```

---

<div class="post-metadata">

**Author:** ![lapidus](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/lapidus/32/1076_2.png) [@lapidus](https://community.stardog.com/u/lapidus)\
**Post date:** [August 9, 2021, 7:35am UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/6 "2021-08-09T07:35:34Z")

</div>

Nice, thank you very much for the feedback.

FYI: Mine produced a DirectHashJoin:

```auto
Slice(offset=0, limit=1000) [#1.0K]
`─ Projection(?p, ?o, ?edgeAttributeProperty, ?edgeAttributeObject) [#24.6M]
   `─ DirectHashJoin(?statement) [#24.6M]
      +─ Bind(COALESCE(GetStatement(<https://graph.datastory.org/angola>, ?p, ?o), "") AS ?statement) [#1]
      │ `─ Scan[SPOC](<https://graph.datastory.org/angola>, ?p, ?o) [#1]
      `─ Scan[SPO](?statement, ?edgeAttributeProperty, ?edgeAttributeObject) [#24.6M]

```

---

<div class="post-metadata">

**Author:** ![system](https://canada1.discourse-cdn.com/flex030/uploads/stardog/original/2X/e/ed66b48a616f505106a4acde3c9cee7e6da9bc67.svg) [@system](https://community.stardog.com/u/system)\
**Post date:** [August 23, 2021, 7:36am UTC](https://community.stardog.com/t/from-30ms-to-7000ms-when-asking-for-edgeattributeproperty/3186/7 "2021-08-23T07:36:11Z")

</div>

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