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980224b4a2
Solely relying on a relation's reltuples/relpages estimate to size the Bloom filters used by amcheck verification makes verification less effective when the estimates are very stale. In extreme cases, verification options that use Bloom filters internally could be totally ineffective, without users receiving any clear indication that certain types of corruption might easily be missed. To fix, use RelationGetNumberOfBlocks() instead of relpages to size the downlink block Bloom filter. Use the same RelationGetNumberOfBlocks() value to derive a minimum size for the heapallindexed Bloom filter, rather than completely trusting reltuples. Verification will still be reasonably effective when the projected/estimated number of Bloom filter elements is at least 1/5 of the final number of elements, which is assured by the new sizing logic. Reported-By: Alexander Korotkov Discussion: https://postgr.es/m/CAH2-Wzk0ke2J42KrNYBKu0Xovjy-sU5ub7PWjgpbsKdAQcL4OA@mail.gmail.com Backpatch: 11-, where downlink/heapallindexed verification were added.
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.