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Robert Haas fd849956cc postgres_fdw: Allow cancellation of transaction control commands. 
Commit f039eaac71, later back-patched
with commit 1b812afb0e, allowed many of
the queries issued by postgres_fdw to fetch remote data to respond to
cancel interrupts in a timely fashion.  However, it didn't do anything
about the transaction control commands, which remained
noninterruptible.

Improve the situation by changing do_sql_command() to retrieve query
results using pgfdw_get_result(), which uses the asynchronous
interface to libpq so that it can check for interrupts every time
libpq returns control.  Since this might result in a situation
where we can no longer be sure that the remote transaction state
matches the local transaction state, add a facility to force all
levels of the local transaction to abort if we've lost track of
the remote state; without this, an apparently-successful commit of
the local transaction might fail to commit changes made on the
remote side.  Also, add a 60-second timeout for queries issue during
transaction abort; if that expires, give up and mark the state of
the connection as unknown.  Drop all such connections when we exit
the local transaction.  Together, these changes mean that if we're
aborting the local toplevel transaction anyway, we can just drop the
remote connection in lieu of waiting (possibly for a very long time)
for it to complete an abort.

This still leaves quite a bit of room for improvement.  PQcancel()
has no asynchronous interface, so if we get stuck sending the cancel
request we'll still hang.  Also, PQsetnonblocking() is not used, which
means we could block uninterruptibly when sending a query.  There
might be some other optimizations possible as well.  Nonetheless,
this allows us to escape a wait for an unresponsive remote server
quickly in many more cases than previously.

Report by Suraj Kharage.  Patch by me and Rafia Sabih.  Review
and testing by Amit Kapila and Tushar Ahuja.

Discussion: http://postgr.es/m/CAF1DzPU8Kx+fMXEbFoP289xtm3bz3t+ZfxhmKavr98Bh-C0TqQ@mail.gmail.com
2017-06-07 15:24:22 -04:00
..
adminpack Fix pg_file_write() error handling. 2017-03-12 19:35:49 -04:00
auth_delay Update copyright for 2016 2016-01-02 14:19:48 -05:00
auto_explain pgindent run for 9.6 2016-06-09 18:02:36 -04:00
bloom Fix typos in comments. 2017-02-06 11:34:15 +02:00
btree_gin Make contrib regression tests safe for Danish locale. 2016-07-21 16:52:35 -04:00
btree_gist Handle contrib's GIN/GIST support function signature changes honestly. 2016-06-09 16:44:25 -04:00
chkpass Avoid returning undefined bytes in chkpass_in(). 2015-02-14 12:20:56 -05:00
citext Repair damage done by citext--1.1--1.2.sql. 2016-07-26 15:32:57 -04:00
cube Fix typos in comments. 2017-02-06 11:34:15 +02:00
dblink Fix ancient connection leak in dblink 2017-03-11 13:32:26 -08:00
dict_int Update copyright for 2016 2016-01-02 13:33:40 -05:00
dict_xsyn Update copyright for 2016 2016-01-02 13:33:40 -05:00
earthdistance Fix typos in comments. 2017-02-06 11:34:15 +02:00
file_fdw Add macros to make AllocSetContextCreate() calls simpler and safer. 2016-08-27 17:50:38 -04:00
fuzzystrmatch Update fuzzystrmatch extension for parallel query. 2016-06-07 11:26:41 -04:00
hstore Update extensions with GIN/GIST support for parallel query. 2016-06-14 13:34:37 -04:00
hstore_plperl Suppress indentation from Data::Dumper in regression tests 2017-05-14 01:13:35 -04:00
hstore_plpython Minor fixes in contrib installation scripts. 2016-06-14 10:47:06 -04:00
intagg Schema-qualify some references to regprocedure. 2016-06-10 10:41:58 -04:00
intarray Fix -e option in contrib/intarray/bench/bench.pl. 2016-08-17 15:51:10 -04:00
isn Fix typos in comments. 2017-02-06 11:34:15 +02:00
lo Update lo extension for parallel query. 2016-06-07 11:26:42 -04:00
ltree Spelling fixes 2017-03-14 13:45:54 -04:00
ltree_plpython Minor fixes in contrib installation scripts. 2016-06-14 10:47:06 -04:00
oid2name Add file version information to most installed Windows binaries. 2014-07-14 14:07:52 -04:00
pageinspect Back-patch portability fixes for contrib/pageinspect/ginfuncs.c. 2016-11-04 12:37:29 -04:00
passwordcheck Update copyright for 2016 2016-01-02 13:33:40 -05:00
pg_buffercache pg_buffercache: Allow huge allocations. 2016-09-15 09:30:37 -04:00
pg_freespacemap Update pg_freespacemap extension for parallel query. 2016-06-09 17:18:16 -04:00
pg_prewarm Update pg_prewarm extension for parallel query. 2016-06-09 17:18:18 -04:00
pg_standby Fix new warnings from GCC 7 2017-05-16 08:52:39 -04:00
pg_stat_statements Fix typos in comments. 2017-02-06 11:34:15 +02:00
pg_trgm Further fix pg_trgm's extraction of trigrams from regular expressions. 2017-04-14 14:52:03 -04:00
pg_visibility Fix bugs in contrib/pg_visibility. 2016-10-01 16:32:55 -04:00
pgcrypto Fix typos in comments. 2017-02-06 11:34:15 +02:00
pgrowlocks Fix handling of multixacts predating pg_upgrade 2016-06-24 18:29:28 -04:00
pgstattuple Minor fixes in contrib installation scripts. 2016-06-14 10:47:06 -04:00
postgres_fdw postgres_fdw: Allow cancellation of transaction control commands. 2017-06-07 15:24:22 -04:00
seg Fix typos in comments. 2017-02-06 11:34:15 +02:00
sepgsql Silence compiler warning in sepgsql 2017-04-06 14:24:41 -07:00
spi Fix typos in comments. 2017-02-06 11:34:15 +02:00
sslinfo Support OpenSSL 1.1.0. 2016-09-15 12:55:38 +03:00
start-scripts Fix typos in comments. 2017-02-06 11:34:15 +02:00
tablefunc Widen query numbers-of-tuples-processed counters to uint64. 2016-03-12 16:05:29 -05:00
tcn Revert CREATE INDEX ... INCLUDING ... 2016-04-08 21:52:13 +03:00
test_decoding Fix race condition leading to hanging logical slot creation. 2017-05-13 14:21:00 -07:00
tsearch2 Fix typos in comments. 2017-02-06 11:34:15 +02:00
tsm_system_rows Update copyright for 2016 2016-01-02 13:33:40 -05:00
tsm_system_time Update copyright for 2016 2016-01-02 13:33:40 -05:00
unaccent Update unaccent extension for parallel query. 2016-06-14 14:55:49 -04:00
uuid-ossp Give a useful error message if uuid-ossp is built without preconfiguration. 2016-12-22 11:19:13 -05:00
vacuumlo Update copyright for 2016 2016-01-02 13:33:40 -05:00
xml2 Fix typos in comments. 2017-02-06 11:34:15 +02:00
contrib-global.mk Respect TEMP_CONFIG when pg_regress_check and friends are called 2016-02-27 12:28:21 -05:00
Makefile Bloom index contrib module 2016-04-01 16:42:24 +03:00
README Rename 'gmake' to 'make' in docs and recommended commands 2014-02-12 17:29:19 -05:00

README 

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.