Allow primary keys to contain address columns sorted by their resolved values. #2854
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This is the GMS part of this change.
Dolt PR: dolthub/dolt#8870
Doltgres PR: dolthub/doltgresql#1214
The goal of the change is to allow for indexes to use an out-of-line variable-length type (like TEXT or BLOB) as a primary key while still storing just the address in the index (instead of being forced to store a prefix of the value).
As a result of this change, any tuple comparison operation may need to resolve a hash in the NodeStore. This poses two complications:
The tuple logic exists at a much lower level than the node store and can't depend on it without creating a dependency cycle. We get around this with a new
ValueStoreinterface that can store and retrieve variable-length bytestrings by their content hash.NodeStoreis the only implementation of this interface, but decoupling the interface from the implementation allows us to not depend onNodeStore's internals when passing it to lower-level code.Tuple comparison operations can now end up doing disk IO, which means they need a context parameter.