When bt_index_parent_check() is called with the heapallindexed option,
allocate a second Bloom filter to fingerprint block numbers that appear
in the downlinks of internal pages. Use Bloom filter probes when
walking the B-Tree to detect missing downlinks. This can detect subtle
problems with page deletion/VACUUM, such as corruption caused by the bug
just fixed in commit 6db4b499.
The downlink Bloom filter is bound in size by work_mem. Its optimal
size is typically far smaller than that of the regular heapallindexed
Bloom filter, especially when the index has high fan-out.
Author: Peter Geoghegan
Reviewer: Teodor Sigaev
Discussion: https://postgr.es/m/CAH2-WznUzY4fWTjm1tBB3JpVz8cCfz7k_qVp5BhuPyhivmWJFg@mail.gmail.com
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.