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Re: First-class Polymorphic joins?

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On 08/13/2015 05:23 PM, Guyren Howe wrote:
It surprises me that no SQL database to my knowledge has polymorphic joins as a first-class feature.

A polymorphic join is where a fk contains not just an id but an indicator of which table it refers to.

I am pretty sure it already does that:

http://www.postgresql.org/docs/9.4/interactive/sql-createtable.html

REFERENCES reftable [ ( refcolumn ) ]

So you could have a "tags" table, that can attach tags to any of a variety of other tables. Rails handles this by including the table name as a string.

This seems a reasonable thing to want to do, and it seems that the database could handle it by combining the fields from the target tables in the result.

I also think migrations ought to be a first-class feature…

So is this the push the ORM into the database day?




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Adrian Klaver
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