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11cf92f6e2
If the toplevel scan/join target list is parallel-safe, postpone generating Gather (or Gather Merge) paths until after the toplevel has been adjusted to return it. This (correctly) makes queries with expensive functions in the target list more likely to choose a parallel plan, since the cost of the plan now reflects the fact that the evaluation will happen in the workers rather than the leader. The original complaint about this problem was from Jeff Janes. If the toplevel scan/join relation is partitioned, recursively apply the changes to all partitions. This sometimes allows us to get rid of Result nodes, because Append is not projection-capable but its children may be. It also cleans up what appears to be incorrect SRF handling from commit e2f1eb0ee30d144628ab523432320f174a2c8966: the old code had no knowledge of SRFs for child scan/join rels. Because we now use create_projection_path() in some cases where we formerly used apply_projection_to_path(), this changes the ordering of columns in some queries generated by postgres_fdw. Update regression outputs accordingly. Patch by me, reviewed by Amit Kapila and by Ashutosh Bapat. Other fixes for this problem (substantially different from this version) were reviewed by Dilip Kumar, Amit Khandekar, and Marina Polyakova. Discussion: http://postgr.es/m/CAMkU=1ycXNipvhWuweUVpKuyu6SpNjF=yHWu4c4US5JgVGxtZQ@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.