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A foreign join planning hook now considers a (foreign-table x function-RTE) INNER join as a push-down candidate when the function expression is IMMUTABLE and otherwise shippable. The remote query absorbs the function call as a FROM-list item (e.g. unnest(...) AS f<rti>(c1, c2, ...)), so the foreign side returns only rows that match the function-produced set and the join executes entirely on the remote. An IMMUTABLE function gives the same result on any server, so the same function RTE can be a push-down candidate for several distinct foreign servers without semantic risk. To keep the planner state consistent across those independent attempts, the per-call stub fpinfo for the function side lives on the joinrel's PgFdwRelationInfo (new outer_func_fpinfo / inner_func_fpinfo), never on the function rel itself, and the function side is detected via rtekind rather than fdw_private. set_foreign_rel_properties() propagates fdwroutine onto a joinrel that pairs a foreign rel with an RTE_FUNCTION rel so GetForeignJoinPaths gets called; the FDW retains full control over whether to actually generate a path. deparseRangeTblRef and deparseColumnRef gain a FUNCTION-RTE branch that emits the function expression and resolves Vars to the generated column aliases. Discussion: https://postgr.es/m/e3af56f9b2f1bd9fdf12aff6ca25b18d%40postgrespro.ru Author: Alexander Pyhalov <a.pyhalov@postgrespro.ru> Reviewed-by: Solaimurugan Vellaipandiyan <drsolaimurugan.v@gmail.com> Reviewed-by: Alexander Korotkov <aekorotkov@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.