apt/apt-pkg/pkgcache.cc, branch 1.1_exp16

remove incorrect optimization branches

2015-09-14T13:22:18Z

These assumptions were once true, but they aren't anymore, so what is supposed to be a speed up is effectively a slowdown [not that it would be noticible]. Usage of SingleArchFindPkg was nuked in a stable update already as the included assumption was actually harmful btw, which is why we should get right of other 'non-harmful' but still untrue assumptions while we can. Git-Dch: Ignore

implement dpkgs vision of interpreting pkg: dependencies

2015-09-14T13:22:18Z

How the Multi-Arch field and pkg: dependencies interact was discussed at DebConf15 in the "MultiArch BoF". dpkg and apt (among other tools like dose) had a different interpretation in certain scenarios which we resolved by agreeing on dpkg view – and this commit realizes this agreement in code. As was the case so far libapt sticks to the idea of trying to hide MultiArch as much as possible from individual frontends and instead translates it to good old SingleArch. There are certainly situations which can be improved in frontends if they know that MultiArch is upon them, but these are improvements – not necessary changes needed to unbreak a frontend. The implementation idea is simple: If we parse a dependency on foo:amd64 the dependency is formed on a package 'foo:amd64' of arch 'any'. This package is provided by package 'foo' of arch 'amd64', but not by 'foo' of arch 'i386'. Both of those foo packages provide each other through (assuming foo is M-A:foreign) to allow a dependency on 'foo' to be satisfied by either foo of amd64 or i386. Packages can also declare to provide 'foo:amd64' which is translated to providing 'foo:amd64:any' as well. This indirection over provides was chosen as the alternative would be to teach dependency resolvers how to deal with architecture specific dependencies – which violates the design idea of avoiding resolver changes, especially as architecture-specific dependencies are a cornercase with quite a few subtil rules. Handling it all over versioned provides as we already did for M-A in general seems much simpler as it just works for them. This switch to :any has actually a "surprising" benefit as well: Even frontends showing a package name via .Name() [which doesn't show the architecture] will display the "architecture" for dependencies in which it was explicitely requested, while we will not show the 'strange' :any arch in FullName(true) [= pretty-print] either. Before you had to specialcase these and by default you wouldn't get these details shown. The only identifiable disadvantage is that this complicates error reporting and handling. apt-get's ShowBroken has existing problems with virtual packages [it just shows the name without any reason], so that has to be worked on eventually. The other case is that detecting if a package is completely unknown or if it was at least referenced somewhere needs to acount for this "split" – not that it makes a practical difference which error is shown… but its one of the improvements possible.

store ':any' pseudo-packages with 'any' as architecture

2015-09-14T13:22:18Z

Previously we had python:any:amd64, python:any:i386, … in the cache and the dependencies of an amd64 package would be on python:any:amd64, of an i386 on python:any:i386 and so on. That seems like a relatively pointless endeavor given that they will all be provided by the same packages and therefore also a waste of space. Git-Dch: Ignore

Cleanup includes after running iwyu

2015-08-17T10:01:45Z

parse packages from all architectures into the cache

2015-08-10T15:27:59Z

Now that we can dynamically create dependencies and provides as needed rather than requiring to know with which architectures we will deal before running we can allow the listparser to parse all records rather than skipping records of "unknown" architectures. This can e.g. happen if a user has foreign architecture packages in his status file without dpkg knowing about this architecture (or apt configured in this way). A sideeffect is that now arch:all packages are (correctly) recorded as available from any Packages file, not just from the native one – which has its downsides for the resolver as mixed-arch source packages can appear in different architectures at different times, but that is the problem of the resolver and dealing with it in the parser is at best a hack (and also depends on a helpful repository). Another sideeffect is that his allows :none packages to appear in Packages files again as we don't do any kind of checks now, but given that they aren't really supported (anymore) by anyone we can live with that.

hide implicit deps in apt-cache again by default

2015-08-10T15:27:58Z

Before MultiArch implicits weren't a thing, so they were hidden by default by definition. Adding them for MultiArch solved many problems, but having no reliable way of detecting which dependency (and provides) is implicit or not causes problems everytime we want to output dependencies without confusing our observers with unneeded implementation details. The really notworthy point here is actually that we keep now a better record of how a dependency came to be so that we can later reason about it more easily, but that is hidden so deep down in the library internals that change is more the problems it solves than the change itself.

use a smaller type for flags storage in the cache

2015-08-10T15:27:58Z

We store very few flags in the cache, so keeping storage space for 8 is enough for all of them and still leaves a few unused bits remaining for future extensions without wasting bytes for nothing. Git-Dch: Ignore

remove the compatibility markers for 4.13 abi

2015-08-10T15:27:58Z

We aren't and we will not be really compatible again with the previous stable abi, so lets drop these markers (which never made it into a released version) for good as they have outlived their intend already. Git-Dch: Ignore

split-up Dependency struct

2015-08-10T15:27:18Z

Having dependency data separated from the link between version/package and the dependency allows use to work on sharing the depdency data a bit as it turns out that many dependencies are in fact duplicates. How many are duplicates various heavily with the sources configured, but for a single Debian release the ballpark is 2 duplicates for each dependency already (e.g. libc6 counts 18410 dependencies, but only 45 unique). Add more releases and the duplicates count only rises to get ~6 for 3 releases. For each architecture a user has configured which given the shear number of dependencies amounts to MBs of duplication. We can cut down on this number, but pay a heavy price for it: In my many releases(3) + architectures(3) test we have a 10% (~ 0.5 sec) increase in cache creationtime, but also 10% less cachesize (~ 10 MB). Further work is needed to rip the whole benefits from this through, so this is just the start. Git-Dch: Ignore

bunch of micro-optimizations for depcache

2015-08-10T15:27:18Z

DepCache functions are called a lot, so if we can squeeze some drops out of them for free we should do so. Takes also the opportunity to remove some whitespace errors from these functions. Git-Dch: Ignore