Doctrine 2 - ORM

Refactor DQL EBNF to use JOIN FETCH as syntax for fetch joins only

Details

  • Type: Improvement Improvement
  • Status: Closed Closed
  • Priority: Critical Critical
  • Resolution: Fixed
  • Affects Version/s: 2.0-ALPHA4
  • Fix Version/s: 2.0-BETA1
  • Component/s: DQL
  • Security Level: All
  • Labels:
    None

Description

There are several problems with the current approach on fetch joins:

1. There is no way to determine in the parser already if a join is fetch or not, this makes it much harder to implement things like @OrderBy or @OrderColumn
2. A DQL like "SELECT u, g.name FROM User u JOIN u.group g" currently tries to partially load the group object instead of just returning g.name as scalar. This is very unintuiative.

Solution, change the EBNF too:

Join                                       ::= ["LEFT" ["OUTER"] | "INNER"] "JOIN" [FETCH] JoinAssociationPathExpression 
                                               ["AS"] AliasIdentificationVariable [("ON" | "WITH") ConditionalExpression]

Question would be how to specify partial object selects.

Romans idea was something like:

select u.{name, other, field, stuff}

However my take is this would again put information into the select clause that might be interesting elsewhere, so

SELECT u FROM User u JOIN FETCH u.group PARTIAL id, name

That way we could add both $isFetchJoin and $isPartial flags to the AST/Join Node plus an additional $partialFields array.

Issue Links

is required for

Improvement - An improvement or enhancement to an existing feature or task. DDC-195 Ordering of associations

  • Major - Major loss of function.
  • Resolved - A resolution has been taken, and it is awaiting verification by reporter. From here issues are either reopened, or are closed.

Activity

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Benjamin Eberlei made changes -
Field Original Value New Value
Link This issue is required for DDC-195 [ DDC-195 ]
Roman S. Borschel made changes -
Status Open [ 1 ] In Progress [ 3 ]
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Benjamin Eberlei added a comment -

Ah just to remember, the idea on the partial fetch syntax was something like:

select u FROM User u.{name, other, field, stuff} JOIN FETCH u.group g.{id, name, baz}
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Benjamin Eberlei added a comment - Ah just to remember, the idea on the partial fetch syntax was something like: select u FROM User u.{name, other, field, stuff} JOIN FETCH u.group g.{id, name, baz}
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Benjamin Eberlei added a comment -

I think this will also make the HINT_PARTIAL_LOAD constant obsolet, since the DQL is already implicitly requesting a partial load.

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Benjamin Eberlei added a comment - I think this will also make the HINT_PARTIAL_LOAD constant obsolet, since the DQL is already implicitly requesting a partial load.
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Roman S. Borschel added a comment -

Regarding HINT_FORCE_PARTIAL_LOAD: Not necessarily, but it might need to be renamed since its still used to decide whether to stub associations with empty collections/proxies.

Anyways, I've played around a bit with different implementations in the last days and I changed my mind regarding changing the fetch join syntax. It has many complications, like more difficult sql construction in the walker, among other things, and of course the fact that it would be a huge bc break.

However, some things will change. "select u.name" will select a scalar value, as you expect. The new syntax for partial object selection will currently be:

select partial u.{id,name}, partial a.{id,city} from User u join u.address a

There will be a new AST node PartialObjectExpression that represents such a construct.

Thats the current state of my progress. Regarding the isFetchJoin/isPartial decisions, we need to find another way and I'm confident there are some other ways.

So far...

Show
Roman S. Borschel added a comment - Regarding HINT_FORCE_PARTIAL_LOAD: Not necessarily, but it might need to be renamed since its still used to decide whether to stub associations with empty collections/proxies. Anyways, I've played around a bit with different implementations in the last days and I changed my mind regarding changing the fetch join syntax. It has many complications, like more difficult sql construction in the walker, among other things, and of course the fact that it would be a huge bc break. However, some things will change. "select u.name" will select a scalar value, as you expect. The new syntax for partial object selection will currently be: select partial u.{id,name}, partial a.{id,city} from User u join u.address a There will be a new AST node PartialObjectExpression that represents such a construct. Thats the current state of my progress. Regarding the isFetchJoin/isPartial decisions, we need to find another way and I'm confident there are some other ways. So far...
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Benjamin Eberlei added a comment -

If we change u.name to retrieving a scalar value always its easy to get all the fetch joins identification variables inside the SELECT already:

If (identificiationVariable) => fetchJoin

Then when the join is found, you can mark the Join as Fetch already.

Show
Benjamin Eberlei added a comment - If we change u.name to retrieving a scalar value always its easy to get all the fetch joins identification variables inside the SELECT already: If (identificiationVariable) => fetchJoin Then when the join is found, you can mark the Join as Fetch already.
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Roman S. Borschel added a comment -

Implemented.

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Roman S. Borschel added a comment - Implemented.
Roman S. Borschel made changes -
Status In Progress [ 3 ] Closed [ 6 ]
Resolution Fixed [ 1 ]
Benjamin Eberlei made changes -
Workflow jira [ 10891 ] jira-feedback [ 15548 ]
Benjamin Eberlei made changes -
Workflow jira-feedback [ 15548 ] jira-feedback2 [ 17412 ]
Benjamin Eberlei made changes -
Workflow jira-feedback2 [ 17412 ] jira-feedback3 [ 19669 ]
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People

  • Assignee:
    Roman S. Borschel
    Reporter:
    Benjamin Eberlei
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Dates

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    Updated:
    Resolved: