LET block, $parent and $current

[Riccardo Tasso]

Hi, I'm trying to write a complex query, in the form:

SELECT @rid, $var FROM MainClass

LET $var = (SELECT FROM OtherClass WHERE ...)

For each element of MainClass, I should find a set of elements of OtherClass (e.g. otherField), filtered using the value of a field of MainClass (e.g. mainField).

Is it right that, inside a LET block, the $parent variable represents the current element of MainClass?

Is it right that, the $current variable represents the current element of OtherClass?

Thanks,

   Riccardo

[Luca Garulli]

Hi,

$parent represent tha parent context, so if you want to get the parent record you've to use:

$parent.$current

The other assumption is correct.

Lvc@

--
 
---
You received this message because you are subscribed to the Google Groups "OrientDB" group.
To unsubscribe from this group and stop receiving emails from it, send an email to orient-databa...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.

[Riccardo Tasso]

I have a problem.

SELECT flatten($var) FROM #14:0 LET $var = ( SELECT $current.otherField, $current.$parent.mainField FROM MainClass )

I expect this query returns a list of documents, each one with otherField and mainField, while mainField is never returned.

What's up?
Riccardo

[Luca Garulli]

Hi,

try to use:

$parent.$current

instead of:

$current.$parent

Lvc@

[Riccardo Tasso]

No way Luca,
   I tried each possible combination and it doesn't work... Can you suggest me a workaround?

Cheers,
   Riccardo

[Luca Garulli]

Hi Riccardo,

try to put as result $parent.$current and see what is printed.

Lvc@

[Riccardo Tasso]

Both those queries return a resultset whose size is equal to size of OtherClass (as expected), but without any field (except the negative @RID field):

SELECT flatten($var) FROM #14:0 LET $var = ( SELECT $parent.$current FROM OtherClass)

SELECT flatten($var) FROM #14:0 LET $var = ( SELECT $current.$parent FROM OtherClass)

Thanks,

   Riccardo

2013/9/8 Luca Garulli <l.ga...@gmail.com>

[Luca Garulli]

Hi Riccardo,

can you expose your database somewhere (nuvolabase.com?) or provide us a script to reproduce it?

Lvc@

[Riccardo Tasso]

Try with this script:

create database memory:temp admin admin memory graph

create class MyClass

insert into MyClass set myField = 1 # assigned to #11:0

insert into MyClass set myField = 2

create class OtherClass

insert into OtherClass set otherField = 11

insert into OtherClass set otherField = 22

select flatten($var) from #11:0 LET $var = (SELECT $current.$parent FROM OtherClass)

I hope it's enough.

Riccardo

2013/9/9 Luca Garulli <l.ga...@gmail.com>

[Luca Garulli]

Hi Riccardo,

thanks for the test case! I found the bug: it was on setting of parent context on sub-queries executed in LET clause.

Fixed in "develop" and in few minutes online on sonatype as 1.6.0-SNAPSHOT.

Lvc@

[Riccardo Tasso]

Any chance to have the fix also in 1.5 brach?

Cheers,

   Riccardo

[Luca Garulli]

Hi Riccardo,

sorry but the 1.6 is planned in few days, so the 1.5.1 was last version of 1.5 branch.

Lvc@

[Carlo Polisini]

My use case is exactly what described in this topic, at least in the first post, but I don't get expected results:

I have defined those two tables, and I am using Document DB on Orient 1.7.8:

Galaxy:

----+------+-----+-------------+--------

#   |@RID  |stars|name         |creator 

----+------+-----+-------------+--------

0   |#13:37|[2]  |milkyway     |zeus    

1   |#13:38|[1]  |coffeeway    |topolino

2   |#13:39|null |cappuccinoway|topolino

Star

----+------+-------+--------+---------

#   |@RID  |planets|name    |creator  

----+------+-------+--------+---------

0   |#15:37|[1]    |Centauri|zeus     

1   |#15:38|null   |Leone   |poseidone

2   |#15:39|null   |Orione  |poseidone

I want to simply select the galaxies that contains at least 1 star with the same creator, so I should get the record #13:37 or #15:37 if I select the child field.

I tried the following but I get 0 results:

select expand($var) from Galaxy LET $var = (SELECT from star where $parent.$current.creator = creator) 

or adding explicit $current in the subquery I get same result:

select expand($var) from Galaxy LET $var = (SELECT from star where $parent.$current.creator = $current.creator)

Another strange thing is that $parent.$current seems to references always the last record of the table:

select expand($var) from Galaxy LET $var = (SELECT expand($parent.$current) from star)

gives:

----+------+-------------+--------

#   |@RID  |name         |creator 

----+------+-------------+--------

0   |#13:39|cappuccinoway|topolino

1   |#13:39|cappuccinoway|topolino

2   |#13:39|cappuccinoway|topolino

3   |#13:39|cappuccinoway|topolino

4   |#13:39|cappuccinoway|topolino

5   |#13:39|cappuccinoway|topolino

6   |#13:39|cappuccinoway|topolino

7   |#13:39|cappuccinoway|topolino

8   |#13:39|cappuccinoway|topolino

----+------+-------------+--------

Any suggestions? To me this a very simple and basic, and I think I am missing some OrientDB syntax structure.

[Marcel Pitch]

Hi Carlo,

I'm working on 2.0-M3 and I've exactly the same problem.

Did you fin a workaround for it ?

Marcel P.

[Carlo Polisini]

Hi Marcel, 

unfortunately I havent found any solutions, I had to drop some features from the app since this bug...

My feeling is that devs are busy with new release of OrientDB 2.0, and in general that OrientDB works better if used in graph mode since you have bidirectional links between entities and querying data will be much easier.

--

---
You received this message because you are subscribed to a topic in the Google Groups "OrientDB" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/orient-database/Xvvs2v4KBMs/unsubscribe.
To unsubscribe from this group and all its topics, send an email to orient-databa...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

--

Carlo Polisini

[Marcel Pitch]

OK,

Thanks Carlo,

Sorry, I didn't precise but I'm working with graph DB and the result is the same.

A test can be easy done by executing this request :

SELECT @rid, $var FROM <VertexClass> LET $var = (SELECT FROM $parent.$current)

The @rid in $var are always the last record one...

Strange...

Or may be, I don't understand the way how to use $parent.$current...

I will ask...

[Marcel Pitch]

Hi Carlo,

I've downloaded the latest 2.0-RC1 version this morning and that solves my problem.

[Carlo Polisini]

That's very good!! Thanks for the feedback!

2014-12-18 10:53 GMT+01:00 Marcel Pitch <marcel...@gmail.com>:

Hi Carlo,

I've downloaded the latest 2.0-RC1 version this morning and that solves my problem.

--

---
You received this message because you are subscribed to a topic in the Google Groups "OrientDB" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/orient-database/Xvvs2v4KBMs/unsubscribe.
To unsubscribe from this group and all its topics, send an email to orient-databa...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

--

Carlo Polisini