Webvelocity/Glorp question (WV 1.0)
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joh
Sep 7, 2010, 3:02:17 AM9/7/10
to WebVelocity
Trying to create two foreign keys between two tables by something like
that:
tableForAaS: aTable
| b1_id b2_id|
(aTable createFieldNamed: 'id' type: platform serial) bePrimaryKey.
b1_id := (aTable createFieldNamed: 'b1_id' type: platform integer) .
b2_id := (aTable createFieldNamed: 'b2_id' type: platform integer) .
aTable addForeignKeyFrom: b1_id to: ((self tableNamed: 'BbS')
fieldNamed: 'id').
aTable addForeignKeyFrom: b2_id toTable: (self tableNamed: 'BbS')
tableForBbS: aTable
(aTable createFieldNamed: 'id' type: platform serial) bePrimaryKey.
(aTable createFieldNamed: 'nr' type: platform integer) beNullable:
false.
I get the error message:
Cannot calculate the join automatically, not enough information
There is no problem defiining only one foreign key, of course.
What can I do?
Joh.
that:
tableForAaS: aTable
| b1_id b2_id|
(aTable createFieldNamed: 'id' type: platform serial) bePrimaryKey.
b1_id := (aTable createFieldNamed: 'b1_id' type: platform integer) .
b2_id := (aTable createFieldNamed: 'b2_id' type: platform integer) .
aTable addForeignKeyFrom: b1_id to: ((self tableNamed: 'BbS')
fieldNamed: 'id').
aTable addForeignKeyFrom: b2_id toTable: (self tableNamed: 'BbS')
tableForBbS: aTable
(aTable createFieldNamed: 'id' type: platform serial) bePrimaryKey.
(aTable createFieldNamed: 'nr' type: platform integer) beNullable:
false.
I get the error message:
Cannot calculate the join automatically, not enough information
There is no problem defiining only one foreign key, of course.
What can I do?
Joh.
Alan Knight
Sep 7, 2010, 9:33:43 AM9/7/10
to WebVelocity
The message means exactly what it says, but it's referring
to the descriptor part, not the table part.
When you define a relationship from an Aa to a Bb, then normally you don't have to say much at all. Glorp will do its best to figure out the types, and based on the types, what foreign key relationships are involved. But if there's more than one foreign key from the Aa table to the Bb table, then it doesn't know which one to use. So you have to define the relationship more explicitly, so in
descriptorForAa: aDescriptor
relationship1 := aDescriptor oneToOneMapping
attributeName: #one;
join: (Join from: b1_id to: ((self tableNamed: 'BbS')
fieldNamed: 'id')).
and similarly for relationship2. Actually, you might even get away with just doing it for one, and it might be smart enough to look for the potential foreign key that isn't already used. But I'm not sure about that.
When you define a relationship from an Aa to a Bb, then normally you don't have to say much at all. Glorp will do its best to figure out the types, and based on the types, what foreign key relationships are involved. But if there's more than one foreign key from the Aa table to the Bb table, then it doesn't know which one to use. So you have to define the relationship more explicitly, so in
descriptorForAa: aDescriptor
relationship1 := aDescriptor oneToOneMapping
attributeName: #one;
join: (Join from: b1_id to: ((self tableNamed: 'BbS')
fieldNamed: 'id')).
and similarly for relationship2. Actually, you might even get away with just doing it for one, and it might be smart enough to look for the potential foreign key that isn't already used. But I'm not sure about that.
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