Re: [HACKERS] Better path-matching for package relocatability (was Re:

Tom Lane wrote:
> Well, more generally what we need is a better match algorithm in
> make_relative_path. After a few moment's thought I propose:
>
> * Determine the common prefix of the compiled-in target_path and
> bin_path (for typical cases this would be "/usr" or "/usr/local";
> worst case is that the common prefix is just "/"). Call everything
> to the right of the common prefix the "tail" of these paths. The
> currently expected scenario is that the tails are "share" and "bin",
> but there might be more than one directory level in them.
>
> * Try to match the tail of the bin_path to the end of the actual binary
> location (my_exec_path without the executable's name).
>
> * If match, take everything to the left of the match in my_exec_path,
> and append the tail of target_path to produce the result.
>
> * If no match, use target_path as-is, same as now.
>
> I think this would get right all of the cases the current code gets
> right, and more generally would work when we need to substitute N
> levels of directory names instead of just one. It may still be a
> few bricks shy of a load, however. Any thoughts?

Sounds fine. When I did the original code, I was very conservative
about where I would look in the fear I might hit something strange. Now
that we have used this code in product with little problem, having it be
more aggressive seems logical.

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