postgresql/contrib
Tom Lane 1bf52d6880 Avoid postgres_fdw crash for a targetlist entry that's just a Param.
foreign_grouping_ok() is willing to put fairly arbitrary expressions into
the targetlist of a remote SELECT that's doing grouping or aggregation on
the remote side, including expressions that have no foreign component to
them at all.  This is possibly a bit dubious from an efficiency standpoint;
but it rises to the level of a crash-causing bug if the expression is just
a Param or non-foreign Var.  In that case, the expression will necessarily
also appear in the fdw_exprs list of values we need to send to the remote
server, and then setrefs.c's set_foreignscan_references will mistakenly
replace the fdw_exprs entry with a Var referencing the targetlist result.

The root cause of this problem is bad design in commit e7cb7ee14: it put
logic into set_foreignscan_references that IMV is postgres_fdw-specific,
and yet this bug shows that it isn't postgres_fdw-specific enough.  The
transformation being done on fdw_exprs assumes that fdw_exprs is to be
evaluated with the fdw_scan_tlist as input, which is not how postgres_fdw
uses it; yet it could be the right thing for some other FDW.  (In the
bigger picture, setrefs.c has no business assuming this for the other
expression fields of a ForeignScan either.)

The right fix therefore would be to expand the FDW API so that the
FDW could inform setrefs.c how it intends to evaluate these various
expressions.  We can't change that in the back branches though, and we
also can't just summarily change setrefs.c's behavior there, or we're
likely to break external FDWs.

As a stopgap, therefore, hack up postgres_fdw so that it won't attempt
to send targetlist entries that look exactly like the fdw_exprs entries
they'd produce.  In most cases this actually produces a superior plan,
IMO, with less data needing to be transmitted and returned; so we probably
ought to think harder about whether we should ship tlist expressions at
all when they don't contain any foreign Vars or Aggs.  But that's an
optimization not a bug fix so I left it for later.  One case where this
produces an inferior plan is where the expression in question is actually
a GROUP BY expression: then the restriction prevents us from using remote
grouping.  It might be possible to work around that (since that would
reduce to group-by-a-constant on the remote side); but it seems like a
pretty unlikely corner case, so I'm not sure it's worth expending effort
solely to improve that.  In any case the right long-term answer is to fix
the API as sketched above, and then revert this hack.

Per bug #15781 from Sean Johnston.  Back-patch to v10 where the problem
was introduced.

Discussion: https://postgr.es/m/15781-2601b1002bad087c@postgresql.org
2019-04-27 13:15:54 -04:00
..
adminpack adminpack: Revoke EXECUTE on pg_logfile_rotate() 2018-05-07 10:10:33 -04:00
amcheck Avoid amcheck inline compression false positives. 2019-02-06 15:54:17 -08:00
auth_delay Update copyright for 2018 2018-01-02 23:30:12 -05:00
auto_explain Fix issues around EXPLAIN with JIT. 2018-10-03 13:11:44 -07:00
bloom Avoid using potentially-under-aligned page buffers. 2018-09-01 15:27:13 -04:00
btree_gin Clean up warnings from -Wimplicit-fallthrough. 2018-05-01 19:35:08 -04:00
btree_gist Improve stability of recently-added regression test case. 2018-10-16 12:01:19 -04:00
citext Fix hashjoin costing mistake introduced with inner_unique optimization. 2018-07-14 11:59:12 -04:00
cube Enforce cube dimension limit in all cube construction functions 2018-08-31 20:24:20 +03:00
dblink Indexes with INCLUDE columns and their support in B-tree 2018-04-07 23:00:39 +03:00
dict_int Avoid unnecessary use of pg_strcasecmp for already-downcased identifiers. 2018-01-26 18:25:14 -05:00
dict_xsyn Avoid unnecessary use of pg_strcasecmp for already-downcased identifiers. 2018-01-26 18:25:14 -05:00
earthdistance Fix earthdistance test suite function name typo. 2018-07-29 12:02:10 -07:00
file_fdw Ensure that foreign scans with lateral refs are planned correctly. 2019-02-07 13:11:13 -05:00
fuzzystrmatch Replace search.cpan.org with metacpan.org 2018-06-29 22:02:20 +09:00
hstore Fix hstore hash function for empty hstores upgraded from 8.4. 2018-11-24 21:17:08 +00:00
hstore_plperl Still further rethinking of build changes for macOS Mojave. 2018-10-18 14:55:23 -04:00
hstore_plpython Fix volatile vs. pointer confusion 2019-03-15 08:37:48 +01:00
intagg Schema-qualify some references to regprocedure. 2016-06-10 10:41:58 -04:00
intarray Avoid crashes in contrib/intarray gist__int_ops (bug #15518) 2018-11-24 08:39:29 +00:00
isn Provide for contrib and pgxs modules to install include files. 2018-07-31 19:58:39 +01:00
jsonb_plperl Still further rethinking of build changes for macOS Mojave. 2018-10-18 14:55:23 -04:00
jsonb_plpython Fix volatile vs. pointer confusion 2019-03-15 08:37:48 +01:00
lo lo: Add test suite 2017-09-14 22:22:59 -04:00
ltree Allow btree comparison functions to return INT_MIN. 2018-10-05 16:01:29 -04:00
ltree_plpython Fix out-of-tree build for transform modules. 2018-09-16 19:13:59 +01:00
oid2name Switch client-side code to include catalog/pg_foo_d.h not pg_foo.h. 2018-04-08 13:59:52 -04:00
pageinspect Fix tuple_data_split() to not open a relation without any lock. 2018-10-01 11:51:07 -04:00
passwordcheck Update copyright for 2018 2018-01-02 23:30:12 -05:00
pg_buffercache Phase 2 of pgindent updates. 2017-06-21 15:19:25 -04:00
pg_freespacemap Default monitoring roles 2017-03-30 14:18:53 -04:00
pg_prewarm Don't auto-restart per-database autoprewarm workers. 2019-03-18 15:30:32 -04:00
pg_standby Avoid using potentially-under-aligned page buffers. 2018-09-01 15:27:13 -04:00
pg_stat_statements Revoke pg_stat_statements_reset() permissions 2018-09-25 09:56:41 +09:00
pg_trgm Post-feature-freeze pgindent run. 2018-04-26 14:47:16 -04:00
pg_visibility Update copyright for 2018 2018-01-02 23:30:12 -05:00
pgcrypto Fix misc typos in comments. 2019-01-23 13:43:41 +02:00
pgrowlocks Replace AclObjectKind with ObjectType 2018-01-19 14:01:15 -05:00
pgstattuple pgstatindex, pageinspect: handle partitioned indexes 2018-05-09 14:22:59 -03:00
postgres_fdw Avoid postgres_fdw crash for a targetlist entry that's just a Param. 2019-04-27 13:15:54 -04:00
seg Provide for contrib and pgxs modules to install include files. 2018-07-31 19:58:39 +01:00
sepgsql Update sepgsql regression test output for getObjectDescription() changes. 2018-05-24 16:11:25 -04:00
spi Prevent accidental linking of system-supplied copies of libpq.so etc. 2018-04-03 16:26:05 -04:00
sslinfo Phase 3 of pgindent updates. 2017-06-21 15:35:54 -04:00
start-scripts Remove contrib/start-scripts/osx/. 2017-11-17 12:53:20 -05:00
tablefunc Update copyright for 2018 2018-01-02 23:30:12 -05:00
tcn Post-feature-freeze pgindent run. 2018-04-26 14:47:16 -04:00
test_decoding Relax overly strict assertion 2019-02-12 18:42:37 -03:00
tsm_system_rows Update copyright for 2018 2018-01-02 23:30:12 -05:00
tsm_system_time Update copyright for 2018 2018-01-02 23:30:12 -05:00
unaccent Make contrib/unaccent's unaccent() function work when not in search path. 2018-09-06 10:49:45 -04:00
uuid-ossp Update copyright for 2018 2018-01-02 23:30:12 -05:00
vacuumlo Avoid double-free in vacuumlo error path. 2019-03-24 15:13:21 -04:00
xml2 Phase 3 of pgindent updates. 2017-06-21 15:35:54 -04:00
contrib-global.mk Respect TEMP_CONFIG when pg_regress_check and friends are called 2016-02-27 12:28:21 -05:00
Makefile Transforms for jsonb to PL/Perl 2018-04-03 09:47:18 -04:00
README Rename 'gmake' to 'make' in docs and recommended commands 2014-02-12 17:29:19 -05:00

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.