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Up to now, index amhandlers were expected to produce a new, palloc'd struct on each call. That requires palloc/pfree overhead, and creates a risk of memory leaks if the caller fails to pfree, and the time taken to fill such a large structure isn't nil. Moreover, we were storing these things in the relcache, eating several hundred bytes for each cached index. There is not anything in these structs that needs to vary at runtime, so let's change the definition so that an amhandler can return a pointer to a "static const" struct of which there's only one copy per index AM. Mark all the core code's IndexAmRoutine pointers const so that we catch anyplace that might still try to change or pfree one. (This is similar to the way we were already handling TableAmRoutine structs. This commit does fix one comment that was infelicitously copied-and-pasted into tableamapi.c.) This commit needs to be called out in the v19 release notes as an API change for extension index AMs. An un-updated AM will still work (as of now, anyway) but it risks memory leaks and will be slower than necessary. Author: Matthias van de Meent <boekewurm+postgres@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAEoWx2=vApYk2LRu8R0DdahsPNEhWUxGBZ=rbZo1EXE=uA+opQ@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.