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0531549801
Commit 0ac5ad5134f2 removed an optimization in multixact.c that skipped fetching members of MultiXactId that were older than our OldestVisibleMXactId value. The reason this was removed is that it is possible for multixacts that contain updates to be older than that value. However, if the caller is certain that the multi does not contain an update (because the infomask bits say so), it can pass this info down to GetMultiXactIdMembers, enabling it to use the old optimization. Pointed out by Andres Freund in 20131121200517.GM7240@alap2.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.