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Commit bbc1376b39 added a new lp_valid[]
array which records whether or not a line pointer was thought to be
valid, but entries could sometimes get set to true in cases where that
wasn't actually safe. Fix that.
Suppose A is a redirect line pointer and B is the other line pointer
to which it points. The old code could mishandle this situation in a
couple of different ways. First, if B was unused, we'd complain about
corruption but still set lp_valid[A] = true, causing later code
to try to access the B as if it were pointing to a tuple. Second,
if B was dead, we wouldn't complain about corruption at all, which is
an oversight, and would also set lp_valid[A] = true, which would
again confuse later code. Fix all that.
In the case where B is a redirect, the old code was correct, but
refactor things a bit anyway so that all of these cases are handled
more symmetrically. Also add an Assert() and some comments.
Andres Freund and Robert Haas
Discussion: http://postgr.es/m/20230323172607.y3lejpntjnuis5vv%40awork3.anarazel.de
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.