mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2025-10-31 14:42:26 -05:00
84 lines
2.4 KiB
Go
84 lines
2.4 KiB
Go
package schema
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import (
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"fmt"
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)
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const (
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InvalidRelation = iota
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HasOneRelation
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BelongsToRelation
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HasManyRelation
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ManyToManyRelation
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)
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type Relation struct {
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Type int
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Field *Field // Has the bun tag defining this relation.
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// Base and Join can be explained with this query:
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//
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// SELECT * FROM base_table JOIN join_table
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JoinTable *Table
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BasePKs []*Field
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JoinPKs []*Field
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OnUpdate string
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OnDelete string
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Condition []string
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PolymorphicField *Field
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PolymorphicValue string
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M2MTable *Table
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M2MBasePKs []*Field
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M2MJoinPKs []*Field
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}
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// References returns true if the table which defines this Relation
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// needs to declare a foreign key constraint, as is the case
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// for 'has-one' and 'belongs-to' relations. For other relations,
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// the constraint is created either in the referencing table (1:N, 'has-many' relations)
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// or the junction table (N:N, 'm2m' relations).
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//
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// Usage of `rel:` tag does not always imply creation of foreign keys (when WithForeignKeys() is not set)
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// and can be used exclusively for joining tables at query time. For example:
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//
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// type User struct {
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// ID int64 `bun:",pk"`
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// Profile *Profile `bun:",rel:has-one,join:id=user_id"`
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// }
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//
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// Creating a FK users.id -> profiles.user_id would be confusing and incorrect,
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// so for such cases References() returns false. One notable exception to this rule
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// is when a Relation is defined in a junction table, in which case it is perfectly
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// fine for its primary keys to reference other tables. Consider:
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//
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// // UsersToGroups maps users to groups they follow.
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// type UsersToGroups struct {
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// UserID string `bun:"user_id,pk"` // Needs FK to users.id
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// GroupID string `bun:"group_id,pk"` // Needs FK to groups.id
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//
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// User *User `bun:"rel:belongs-to,join:user_id=id"`
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// Group *Group `bun:"rel:belongs-to,join:group_id=id"`
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// }
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//
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// Here BooksToReaders has a composite primary key, composed of other primary keys.
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func (r *Relation) References() bool {
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allPK := true
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nonePK := true
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for _, f := range r.BasePKs {
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allPK = allPK && f.IsPK
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nonePK = nonePK && !f.IsPK
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}
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// Erring on the side of caution, only create foreign keys
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// if the referencing columns are part of a composite PK
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// in the junction table of the m2m relationship.
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effectsM2M := r.Field.Table.IsM2MTable && allPK
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return (r.Type == HasOneRelation || r.Type == BelongsToRelation) && (effectsM2M || nonePK)
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}
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func (r *Relation) String() string {
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return fmt.Sprintf("relation=%s", r.Field.GoName)
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}
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