mirror of
https://github.com/postgres/postgres.git
synced 2025-08-30 06:01:21 +03:00
da8f3ebf30
While converting expressions in an upper-level plan node so that they reference Vars and expressions provided by the input plan node(s), don't convert plain Const items, even if there happens to be a matching Const in the input. It's silly to do so because a Var is more expensive to execute than a Const. Moreover, converting can fool ExecCheckPlanOutput's check that an insert or update query inserts nulls into dropped columns, leading to "query provides a value for a dropped column" errors during INSERT or UPDATE on a table with a dropped column. We could solve this by making that check more complicated, but I don't see the point; this fix should save a marginal number of cycles, and it also makes for less messy EXPLAIN output, as shown by the ensuing regression test result changes. Per report from Pavel Hanák. I have not incorporated a test case based on that example, as there doesn't seem to be a simple way of checking this in isolation without making a bunch of assumptions about other planner and SQL-function behavior. Back-patch to 9.6. This setrefs.c behavior exists much further back, but there is not currently reason to think that it causes problems before 9.6. Discussion: <83shraampf.fsf@is-it.eu>
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.