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Commit e7cb7ee145
provided basic
infrastructure for allowing a foreign data wrapper or custom scan
provider to replace a join of one or more tables with a scan.
However, this infrastructure failed to take into account the need
for possible EvalPlanQual rechecks, and ExecScanFetch would fail
an assertion (or just overwrite memory) if such a check was attempted
for a plan containing a pushed-down join. To fix, adjust the EPQ
machinery to skip some processing steps when scanrelid == 0, making
those the responsibility of scan's recheck method, which also has
the responsibility in this case of correctly populating the relevant
slot.
To allow foreign scans to gain control in the right place to make
use of this new facility, add a new, optional RecheckForeignScan
method. Also, allow a foreign scan to have a child plan, which can
be used to correctly populate the slot (or perhaps for something
else, but this is the only use currently envisioned).
KaiGai Kohei, reviewed by Robert Haas, Etsuro Fujita, and Kyotaro
Horiguchi.
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.