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bc436e4a91
If the regex compiler can see that a regex is unsatisfiable (for example, '$foo') then it may emit an NFA having no arcs. pg_trgm's packGraph function did the wrong thing in this case; it would access off the end of a work array, and with bad luck could produce a corrupted output data structure causing more problems later. This could end with wrong answers or crashes in queries using a pg_trgm GIN or GiST index with such a regex. Fix by not trying to de-duplicate if there aren't at least 2 arcs. Per bug #17830 from Alexander Lakhin. Back-patch to all supported branches. Discussion: https://postgr.es/m/17830-57ff5f89bdb02b09@postgresql.org
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.