Draft: Mapping a single property to multiple columns #24909
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Part of #13947 The idea here is that a property can contain pseudo-properties that generally don't act like properties in the model, but form the basis for mapping to a column after extracting a value from the outer property. Why properties? Because they have all the metadata needed to allow the facets of columns to be configured? Why not relational only? Cosmos won't use this, but in-memory will be able to understand it.
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@AndriySvyryd This is mostly for you to look at and comment on whether this is going in a reasonable direction. Lots still left to do, but EnsureCreated and SaveChanges works for the example in SqlServerEndToEndTest. |
| ? ((IPseudoProperty)propertyBase).ValueExtractor( | ||
| ReadPropertyValue(((IPseudoProperty)propertyBase).OuterProperty)) |
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Why not repurpose the Getter?
| ? ((IPseudoProperty)propertyBase).ValueExtractor( | |
| ReadPropertyValue(((IPseudoProperty)propertyBase).OuterProperty)) | |
| ? propertyBase.GetGetter().GetClrValue(ReadPropertyValue(((IPseudoProperty)propertyBase).OuterProperty)) |
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How will the shadow pseudo properties be handled?
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I don't think shadow pseudo properties are a thing. A shadow property has storage in the state manager and no storage in the CLR type. In this case, the property has no storage of it's own because the value doesn't exist in this form in application code at all.
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Yes, the outer property is basically a complex property if the CLR type contains properties that can be used for pseudo-properties. If the outer type is something like a string then the pseudo-properties don't map to a CLR property of their owns but still only keep state in the entity object. We might need a different name for this.
| /// Once the model is built, <see cref="IProperty" /> represents a read-only view of the same metadata. | ||
| /// </para> | ||
| /// </summary> | ||
| public interface IReadOnlyPseudoProperty : IReadOnlyProperty, IPseudoProperty |
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This interface seems unnecessary. A property is a pseudo property if OuterProperty is not null
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At the moment each pseudo-property will have three additional references:
- The outer property
- The value extractor delegate
- The value extractor expression
Do you think it's better to have these three references available but null on every property, rather than introduce a new type? (I'm very much on the fence.)
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Yes, though value extractors might not be needed per my previous comment
Cosmos will use this. |
Part of #13947
The idea here is that a property can contain pseudo-properties that generally don't act like properties in the model, but form the basis for mapping to a column after extracting a value from the outer property.
Why properties? Because they have all the metadata needed to allow the facets of columns to be configured?
Why not relational only? Cosmos won't use this, but in-memory will be able to understand it.