Create PackageKey to replace PackageId, including version dependency information
|Reported by:||ezyang||Owned by:||ezyang|
|Type of failure:||None/Unknown||Test Case:|
|Related Tickets:||Differential Revisions:|
Description (last modified by ezyang)
This ticket is our latest attack on the problem, summarized as: add a version dependency hash to the PackageId (NOT the InstalledPackageId) associated with packages in the database. This approach is distinguished from the prior attempts as follows:
- We make no attempt to support multiple installations of different ways or ABI-compatible versions of a library (e.g. with/without optimizations.) This corresponds to supporting multiple InstalledPackageIds in a database; in our case, we're supporting multiple PackageId.
- We do not have to deal with conflicting "instances" in GHC's package resolver: multiple instances can be simultaneously loaded and used in a single compiled program. This is because PackageIds are baked into the exported linker symbols, so different versions will have different names and can peacefully coexist.
- We do not have to deal with the delicate ordering problem of calculating an ABI hash when configuring a package, which is prior to when we actually know it (ABI hash is only known after compilation), because our hash is based ONLY on dependency resolution choice.
- In absence of preference for previously installed packages, our Cabal dependency resolution stays exactly the same: Cabal picks versions, and from these choices we calculate the dependency hashes. With preference, we will have to do a little more work.
- We do not attempt to garbage collect old packages. Because we are not dependent on ABI, there is not an explosion of installed pacakges from package development; new installed packages only occur when version numbers are bumped up, or packages are installed in a combinatorially different fashion.
Change History (10)
comment:9 Changed 13 months ago by ezyang
- Summary changed from Extend PackageId to include version dependency information to Create PackageKey to replace PackageId, including version dependency information