Extensions

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Extensions

A series of patches implements extensions support for dump and restore for PostgreSQL. In order to reach this goal, several things need to happen, and the patch is quite large by now. This is the diffstat of the cumulative branch:

$ git diff master..|diffstat
contrib/adminpack/Makefile                               |    3 
contrib/adminpack/adminpack.control.in                   |    3 
contrib/btree_gin/Makefile                               |    3 
contrib/btree_gin/btree_gin.control.in                   |    3 
contrib/btree_gin/btree_gin.sql.in                       |    2 
contrib/btree_gin/expected/install_btree_gin.out         |    2 
contrib/btree_gin/sql/install_btree_gin.sql              |    4 
contrib/btree_gist/Makefile                              |    3 
contrib/btree_gist/btree_gist.control.in                 |    3 
contrib/btree_gist/btree_gist.sql.in                     |    2 
contrib/btree_gist/expected/init.out                     |    2 
contrib/btree_gist/sql/init.sql                          |    4 
contrib/chkpass/Makefile                                 |    3 
contrib/chkpass/chkpass.control.in                       |    3 
contrib/chkpass/chkpass.sql.in                           |    2 
contrib/citext/Makefile                                  |    3 
contrib/citext/citext.control.in                         |    3 
contrib/citext/citext.sql.in                             |    2 
contrib/citext/expected/citext.out                       |    3 
contrib/citext/expected/citext_1.out                     |    3 
contrib/citext/sql/citext.sql                            |    4 
contrib/cube/Makefile                                    |    3 
contrib/cube/cube.control.in                             |    3 
contrib/cube/cube.sql.in                                 |    2 
contrib/cube/expected/cube.out                           |    2 
contrib/cube/expected/cube_1.out                         |    2 
contrib/cube/expected/cube_2.out                         |    2 
contrib/cube/sql/cube.sql                                |    4 
contrib/dblink/Makefile                                  |    2 
contrib/dblink/dblink.control.in                         |    3 
contrib/dblink/dblink.sql.in                             |    2 
contrib/dblink/expected/dblink.out                       |    2 
contrib/dblink/sql/dblink.sql                            |    4 
contrib/dict_int/Makefile                                |    3 
contrib/dict_int/dict_int.control.in                     |    3 
contrib/dict_int/dict_int.sql.in                         |    2 
contrib/dict_int/expected/dict_int.out                   |    2 
contrib/dict_int/sql/dict_int.sql                        |    4 
contrib/dict_xsyn/Makefile                               |    3 
contrib/dict_xsyn/dict_xsyn.control.in                   |    3 
contrib/dict_xsyn/dict_xsyn.sql.in                       |    2 
contrib/dict_xsyn/expected/dict_xsyn.out                 |    2 
contrib/dict_xsyn/sql/dict_xsyn.sql                      |    4 
contrib/earthdistance/Makefile                           |    3 
contrib/earthdistance/earthdistance.control.in           |    3 
contrib/earthdistance/earthdistance.sql.in               |    2 
contrib/earthdistance/expected/earthdistance.out         |    3 
contrib/earthdistance/sql/earthdistance.sql              |    6 
contrib/fuzzystrmatch/Makefile                           |    3 
contrib/fuzzystrmatch/fuzzystrmatch.control.in           |    3 
contrib/fuzzystrmatch/fuzzystrmatch.sql.in               |    2 
contrib/hstore/Makefile                                  |   17 +
contrib/hstore/expected/hstore.out                       |    6 
contrib/hstore/hstore.control.in                         |    3 
contrib/hstore/hstore.sql.in                             |    2 
contrib/hstore/sql/hstore.sql                            |    6 
contrib/intagg/Makefile                                  |    3 
contrib/intagg/int_aggregate.control.in                  |    3 
contrib/intarray/Makefile                                |    3 
contrib/intarray/_int.sql.in                             |    2 
contrib/intarray/expected/_int.out                       |    2 
contrib/intarray/intarray.control.in                     |    5 
contrib/intarray/sql/_int.sql                            |    4 
contrib/isn/Makefile                                     |    3 
contrib/isn/isn.control.in                               |    3 
contrib/isn/isn.sql.in                                   |    2 
contrib/lo/Makefile                                      |    3 
contrib/lo/lo.control.in                                 |    3 
contrib/lo/lo.sql.in                                     |    2 
contrib/ltree/Makefile                                   |    3 
contrib/ltree/expected/ltree.out                         |    2 
contrib/ltree/ltree.control.in                           |    3 
contrib/ltree/ltree.sql.in                               |    2 
contrib/ltree/sql/ltree.sql                              |    4 
contrib/pageinspect/Makefile                             |    3 
contrib/pageinspect/pageinspect.control.in               |    3 
contrib/pageinspect/pageinspect.sql.in                   |    2 
contrib/pg_buffercache/Makefile                          |    3 
contrib/pg_buffercache/pg_buffercache.control.in         |    3 
contrib/pg_buffercache/pg_buffercache.sql.in             |    2 
contrib/pg_freespacemap/Makefile                         |    3 
contrib/pg_freespacemap/pg_freespacemap.control.in       |    3 
contrib/pg_freespacemap/pg_freespacemap.sql.in           |    2 
contrib/pg_stat_statements/Makefile                      |    3 
contrib/pg_stat_statements/pg_stat_statements.control.in |    8 
contrib/pg_stat_statements/pg_stat_statements.sql.in     |    2 
contrib/pg_trgm/Makefile                                 |    3 
contrib/pg_trgm/expected/pg_trgm.out                     |    2 
contrib/pg_trgm/pg_trgm.control.in                       |    3 
contrib/pg_trgm/pg_trgm.sql.in                           |    2 
contrib/pg_trgm/sql/pg_trgm.sql                          |    4 
contrib/pgcrypto/Makefile                                |    2 
contrib/pgcrypto/expected/init.out                       |    2 
contrib/pgcrypto/pgcrypto.control.in                     |    3 
contrib/pgcrypto/pgcrypto.sql.in                         |    2 
contrib/pgcrypto/sql/init.sql                            |    4 
contrib/pgrowlocks/Makefile                              |    3 
contrib/pgrowlocks/pgrowlocks.control.in                 |    3 
contrib/pgrowlocks/pgrowlocks.sql.in                     |    2 
contrib/pgstattuple/Makefile                             |    3 
contrib/pgstattuple/pgstattuple.control.in               |    3 
contrib/pgstattuple/pgstattuple.sql.in                   |    2 
contrib/seg/Makefile                                     |    3 
contrib/seg/expected/seg.out                             |    2 
contrib/seg/expected/seg_1.out                           |    2 
contrib/seg/seg.control.in                               |    3 
contrib/seg/seg.sql.in                                   |    2 
contrib/seg/sql/seg.sql                                  |    4 
contrib/spi/Makefile                                     |    4 
contrib/spi/auto_username.control.in                     |    4 
contrib/spi/autoinc.control.in                           |    3 
contrib/spi/autoinc.sql.in                               |    2 
contrib/spi/insert_username.sql.in                       |    2 
contrib/spi/moddatetime.control.in                       |    3 
contrib/spi/moddatetime.sql.in                           |    2 
contrib/spi/refint.control.in                            |    3 
contrib/spi/refint.sql.in                                |    2 
contrib/spi/timetravel.control.in                        |    3 
contrib/spi/timetravel.sql.in                            |    2 
contrib/sslinfo/Makefile                                 |    3 
contrib/sslinfo/sslinfo.control.in                       |    3 
contrib/sslinfo/sslinfo.sql.in                           |    2 
contrib/tablefunc/Makefile                               |    3 
contrib/tablefunc/expected/tablefunc.out                 |    2 
contrib/tablefunc/sql/tablefunc.sql                      |    4 
contrib/tablefunc/tablefunc.control.in                   |    3 
contrib/tablefunc/tablefunc.sql.in                       |    2 
contrib/test_parser/Makefile                             |    3 
contrib/test_parser/expected/test_parser.out             |    2 
contrib/test_parser/sql/test_parser.sql                  |    4 
contrib/test_parser/test_parser.control.in               |    3 
contrib/test_parser/test_parser.sql.in                   |    2 
contrib/tsearch2/Makefile                                |    3 
contrib/tsearch2/expected/tsearch2.out                   |    2 
contrib/tsearch2/expected/tsearch2_1.out                 |    2 
contrib/tsearch2/sql/tsearch2.sql                        |    4 
contrib/tsearch2/tsearch2.control.in                     |    3 
contrib/tsearch2/tsearch2.sql.in                         |    2 
contrib/unaccent/Makefile                                |    3 
contrib/unaccent/expected/unaccent.out                   |    2 
contrib/unaccent/sql/unaccent.sql                        |    4 
contrib/unaccent/unaccent.control.in                     |    3 
contrib/unaccent/unaccent.sql.in                         |    2 
contrib/uuid-ossp/Makefile                               |    3 
contrib/uuid-ossp/uuid-ossp.control.in                   |    3 
contrib/uuid-ossp/uuid-ossp.sql.in                       |    2 
contrib/xml2/Makefile                                    |    3 
contrib/xml2/expected/xml2.out                           |    2 
contrib/xml2/expected/xml2_1.out                         |    2 
contrib/xml2/pgxml.sql.in                                |    2 
contrib/xml2/sql/xml2.sql                                |    4 
contrib/xml2/xml2.control.in                             |    4 
doc/src/sgml/catalogs.sgml                               |  131 ++++++++++++++
doc/src/sgml/extend.sgml                                 |  118 ++++++++++++
doc/src/sgml/func.sgml                                   |  123 +++++++++++++
doc/src/sgml/ref/allfiles.sgml                           |    2 
doc/src/sgml/ref/alter_conversion.sgml                   |   10 +
doc/src/sgml/ref/alter_opclass.sgml                      |   10 +
doc/src/sgml/ref/alter_operator.sgml                     |   10 +
doc/src/sgml/ref/alter_opfamily.sgml                     |   10 +
doc/src/sgml/ref/alter_tsconfig.sgml                     |   10 +
doc/src/sgml/ref/alter_tsdictionary.sgml                 |   10 +
doc/src/sgml/ref/alter_tsparser.sgml                     |   10 +
doc/src/sgml/ref/alter_tstemplate.sgml                   |   10 +
doc/src/sgml/ref/create_extension.sgml                   |  144 +++++++++++++++
doc/src/sgml/ref/drop_extension.sgml                     |  115 ++++++++++++
doc/src/sgml/reference.sgml                              |    2 
doc/src/sgml/xfunc.sgml                                  |   30 +++
src/backend/access/transam/xlog.c                        |   97 ----------
src/backend/catalog/Makefile                             |    1 
src/backend/catalog/dependency.c                         |  140 +++++++++++----
src/backend/catalog/heap.c                               |   23 +-
src/backend/catalog/namespace.c                          |   27 ++
src/backend/catalog/objectaddress.c                      |   14 +
src/backend/catalog/pg_aggregate.c                       |    7 
src/backend/catalog/pg_conversion.c                      |    7 
src/backend/catalog/pg_depend.c                          |  109 +++++++++++
src/backend/catalog/pg_namespace.c                       |   13 +
src/backend/catalog/pg_operator.c                        |    7 
src/backend/catalog/pg_proc.c                            |    7 
src/backend/catalog/pg_type.c                            |    8 
src/backend/catalog/system_views.sql                     |    3 
src/backend/commands/Makefile                            |    3 
src/backend/commands/alter.c                             |  226 ++++++++++++++++++++++++
src/backend/commands/comment.c                           |    6 
src/backend/commands/conversioncmds.c                    |   50 +++++
src/backend/commands/extension.c                         | 1322 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
src/backend/commands/foreigncmds.c                       |   19 ++
src/backend/commands/functioncmds.c                      |   39 ++--
src/backend/commands/opclasscmds.c                       |  170 ++++++++++++++++++
src/backend/commands/operatorcmds.c                      |   51 +++++
src/backend/commands/proclang.c                          |    7 
src/backend/commands/tsearchcmds.c                       |  194 ++++++++++++++++++++
src/backend/commands/typecmds.c                          |   17 +
src/backend/nodes/copyfuncs.c                            |   29 +++
src/backend/nodes/equalfuncs.c                           |   25 ++
src/backend/parser/gram.y                                |  169 +++++++++++++++++-
src/backend/rewrite/rewriteDefine.c                      |    7 
src/backend/tcop/utility.c                               |   42 ++++
src/backend/utils/adt/genfile.c                          |  130 +++++++++++++-
src/backend/utils/init/postinit.c                        |    4 
src/backend/utils/misc/Makefile                          |    2 
src/backend/utils/misc/cfparser.c                        |  115 ++++++++++++
src/backend/utils/misc/guc-file.l                        |   25 +-
src/backend/utils/misc/guc.c                             |  160 +++++++++++++++--
src/bin/pg_dump/common.c                                 |    6 
src/bin/pg_dump/pg_dump.c                                |  543 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----
src/bin/pg_dump/pg_dump.h                                |   11 +
src/bin/pg_dump/pg_dump_sort.c                           |    7 
src/bin/psql/command.c                                   |    3 
src/bin/psql/describe.c                                  |   50 +++++
src/bin/psql/describe.h                                  |    3 
src/bin/psql/help.c                                      |    1 
src/include/catalog/dependency.h                         |   40 ++++
src/include/catalog/indexing.h                           |    6 
src/include/catalog/namespace.h                          |    2 
src/include/catalog/pg_extension.h                       |   61 ++++++
src/include/catalog/pg_proc.h                            |   21 +-
src/include/catalog/toasting.h                           |    1 
src/include/commands/alter.h                             |    9 
src/include/commands/conversioncmds.h                    |    3 
src/include/commands/defrem.h                            |   15 +
src/include/commands/extension.h                         |   70 +++++++
src/include/commands/typecmds.h                          |    1 
src/include/nodes/nodes.h                                |    2 
src/include/nodes/parsenodes.h                           |   21 ++
src/include/parser/kwlist.h                              |    1 
src/include/utils/builtins.h                             |    7 
src/include/utils/cfparser.h                             |   18 +
src/include/utils/genfile.h                              |   22 ++
src/include/utils/guc.h                                  |   11 +
src/makefiles/pgxs.mk                                    |   23 ++
232 files changed, 5042 insertions(+), 383 deletions(-)

Overview

The extension patch has to be considered with the dump and restore support in mind. About all that is done is to that end, there is very few extra in there. The goal is for pg_dump not to output the extension's install script, that is maintained separately from the database objects. That allows for easier restores too, when the extension needs to be upgraded. What we want to see in the dump is:

 CREATE EXTENSION citext WITH SCHEMA foo NO USER DATA;

For schema support, see the discussion above.

Some extension will install tables where users will be able to edit the data, or use commands and functions that will change the data for them. The line of though here is that the data will change and that we want to have them as part of the dump, because the maintenance of those data is not done in the extension's SCM but in the database.

User Interface

psql

There's both \dx to list installed extensions and \dx+ to list installed and available extensions.

dfontaine=# \dx
                                                List of extensions
 Schema |        Name        | Version  |                               Description                               
--------+--------------------+----------+-------------------------------------------------------------------------
 utils  | adminpack          | 9.1devel | Administrative functions for PostgreSQL
 utils  | seg                | 9.1devel | data type for representing line segments, or floating point intervals
 utils  | refint             | 9.1devel | functions for implementing referential integrity
 utils  | hstore             | 9.1devel | storing sets of key/value pairs
 utils  | pg_freespacemap    | 9.1devel | examine the free space map (FSM)
 utils  | pgstattuple        | 9.1devel | obtain tuple-level statistics
 utils  | citext             | 9.1devel | case-insensitive character string type
 utils  | dict_int           | 9.1devel | example of an add-on dictionary template for full-text search
 utils  | pg_trgm            | 9.1devel | determine the similarity of text, with indexing support
 utils  | pageinspect        | 9.1devel | inspect the contents of database pages at a low level
 utils  | pgcrypto           | 9.1devel | cryptographic functions
 utils  | intarray           | 9.1devel | one-dimensional arrays of integers: functions, operators, index support
 utils  | test_parser        | 9.1devel | example of a custom parser for full-text search
 utils  | pg_stat_statements | 9.1devel | tracking execution statistics of all SQL statements executed
 utils  | int_aggregate      | 9.1devel | integer aggregator and an enumerator (obsolete)
 utils  | tablefunc          | 9.1devel | various functions that return tables, including crosstab(text sql)
 utils  | chkpass            | 9.1devel | Store crypt()ed passwords
 utils  | lo                 | 9.1devel | managing Large Objects
 utils  | dblink             | 9.1devel | connect to other PostgreSQL databases from within a database
 utils  | timetravel         | 9.1devel | functions for implementing time travel
 utils  | pgrowlocks         | 9.1devel | show row locking information for a specified table
 utils  | pg_buffercache     | 9.1devel | examine the shared buffer cache in real time
 utils  | btree_gin          | 9.1devel | GIN support for common types BTree operators
 utils  | moddatetime        | 9.1devel | functions for tracking last modification time
 utils  | unaccent           | 9.1devel | text search dictionary that removes accents
 utils  | cube               | 9.1devel | data type for representing multidimensional cubes
 utils  | dict_xsyn          | 9.1devel | example of an add-on dictionary template for full-text search
 utils  | ltree              | 9.1devel | data type for hierarchical tree-like structure
 utils  | btree_gist         | 9.1devel | GiST support for common types BTree operators
 utils  | earthdistance      | 9.1devel | calculating great circle distances on the surface of the Earth
 utils  | autoinc            | 9.1devel | functions for autoincrementing fields
 utils  | tsearch2           | 9.1devel | backwards-compatible text search functionality (pre-8.3)
 utils  | auto_username      | 9.1devel | functions for tracking who changed a table
 utils  | fuzzystrmatch      | 9.1devel | determine similarities and distance between strings
 utils  | isn                | 9.1devel | data types for the international product numbering standards
(35 rows)

The function pg_extension_objects() is useful both for end-users and extension authors who will want to find their objects oid easily to manage upgrades, e.g.

dfontaine=# select * from pg_extension_objects('unaccent');
     class      | classid | objid |                               objdesc                               
----------------+---------+-------+---------------------------------------------------------------------
 pg_extension   |    3996 | 18009 | extension unaccent
 pg_proc        |    1255 | 18010 | function utils.unaccent(regdictionary,text)
 pg_proc        |    1255 | 18011 | function utils.unaccent(text)
 pg_proc        |    1255 | 18012 | function utils.unaccent_init(internal)
 pg_proc        |    1255 | 18013 | function utils.unaccent_lexize(internal,internal,internal,internal)
 pg_ts_template |    3764 | 18014 | text search template unaccent
 pg_ts_dict     |    3600 | 18015 | text search dictionary unaccent
(7 rows)

catalog, system view, functions

The calalog has minimal information here. All extension related operations are super-user only, and we only need a name, a version string and a custom_variable_classes setting, as detailed later.

dfontaine=# \d pg_extension
 Table "pg_catalog.pg_extension"
    Column    | Type | Modifiers 
--------------+------+-----------
 extname      | name | not null
 extversion   | text | 
 custom_class | text | 
Indexes:
    "pg_extension_name_index" UNIQUE, btree (extname)
    "pg_extension_oid_index" UNIQUE, btree (oid)

The pg_extensions system view will also list available extensions, and offers an "installed" column to sort that out:

dfontaine=# \d pg_extensions
        View "pg_catalog.pg_extensions"
         Column          |  Type   | Modifiers 
-------------------------+---------+-----------
 name                    | name    | 
 version                 | text    | 
 custom_variable_classes | text    | 
 comment                 | text    |  
 installed               | boolean | 

Some utility functions are available, intended for extension authoring. See later for details:

dfontaine=# \df pg_ext*
                                                                                 List of functions
   Schema   |            Name             | Result data type |                                            Argument data types                                             |  Type  
------------+-----------------------------+------------------+------------------------------------------------------------------------------------------------------------+--------
 pg_catalog | pg_extension_flag_dump      | boolean          | oid                                                                                                        | normal
 pg_catalog | pg_extension_objects        | SETOF record     | name name, OUT class regclass, OUT classid oid, OUT objid oid, OUT objdesc text                            | normal
 pg_catalog | pg_extension_with_user_data | boolean          |                                                                                                            | normal
 pg_catalog | pg_extensions               | SETOF record     | OUT name name, OUT version text, OUT custom_variable_classes text, OUT comment text, OUT installed boolean | normal
(4 rows)

commands

Basically, you can CREATE and DROP an extension, and also ALTER it.

dfontaine=# \h create extension
Command:     CREATE EXTENSION
Description: define and install a new extension
Syntax:
CREATE EXTENSION extension_name
    [ [ WITH ] [ [ NO ] USER DATA ]
           [ SCHEMA [=] schema ]
           [ ENCODING [=] encoding ]
dfontaine=# \h drop extension                                               
Command:     DROP EXTENSION
Description: remove a tablespace
Syntax:
DROP EXTENSION [ IF EXISTS ] extension_name [ CASCADE | RESTRICT ]

Also

ALTER EXTENSION extension_name SET SCHEMA schema_name;

user data and extensions

The extension's patches goal is for pg_dump *NOT* to care about extension's objects, because they are maintained in some repository out there, not in the database. There's an exception here, when the extension installs tables (or anything, really) that the user can edit, directly or through some facilities given by the extension. Now we need to dump those as well.

Extension authors have a function they can call from their scripts to flag some objects are necessary to dump, and the documentation contains this example:

+ DO $$
+ BEGIN
+ IF pg_extension_with_user_data() THEN
+   create schema foo;
+   create table foo.bar(id serial primary key);
+   perform pg_extension_flag_dump('foo.bar_id_seq'::regclass);
+   perform pg_extension_flag_dump('foo.bar::regclass);
+ END IF;
+ END;
+ $$;

Such flags will make it so that pg_dump will dump the objects separately. The idea is that the dependency between the object and its extension is changed from DEPENDENCY_INTERNAL (no dump) to DEPENDENCY_NORMAL (dump).

schema and extensions

The schema support has been asked for on the -hackers list and is a simple search and replace of the @extschema@ placeholder in the extension's script, replacing it by the user entered schema in the CREATE EXTENSION command, which defaults to 'public'.

Another patch proposes the ALTER EXTENSION SET SCHEMA command: we are able to track all extension's object, so we are able to run the SET SCHEMA command on all of them. That's an optional sugar ish facility that is seen as a great value :)

pg_dump support

The pg_dump command has been patched so that it will not consider any object that has a direct DEPENDENDY_INTERNAL pg_depend entry to the extension's oid. That's about the only goal of all this work.

Of course we have some special cases to care about or it wouldn't be funny, such as the following:

! 	if (g_fout->remoteVersion >= 90100)
! 	{
! 		/*
! 		 * So we want the namespaces, but we want to filter out any
! 		 * namespace created by an extension's script. That's unless the
! 		 * user went over his head and created objects into the extension's
! 		 * schema: we now want the schema not to be filtered out to avoid:
! 		 *
! 		 *   pg_dump: schema with OID 77869 does not exist
! 		 */
! 		appendPQExpBuffer(query, "SELECT n.tableoid, n.oid, n.nspname, "
! 						  "(%s nspowner) AS rolname, "
! 						  "n.nspacl "
! 						  "  FROM pg_namespace n "
! 						  " WHERE n.nspname != 'information_schema' "
! 						  "   AND CASE WHEN (SELECT count(*) "
! 						  "                    FROM pg_depend "
! 						  "                   WHERE refobjid = n.oid and deptype != 'p') > 0 "
! 						  "            THEN EXISTS( "
! 						  "WITH RECURSIVE depends AS ( "
! 						  " select n.oid as nsp, objid, refobjid, array[refobjid] as deps "
! 						  "   from pg_depend "
! 						  "  where refobjid = n.oid and deptype != 'p' "
! 						  " UNION ALL "
! 						  " select p.nsp, p.objid, d.refobjid, deps || d.refobjid "
! 						  "   from pg_depend d JOIN depends p ON d.objid = p.objid "
! 						  "  where d.deptype != 'p' and not d.refobjid = any(deps) "
! 						  "        and not (d.refclassid = 'pg_extension'::regclass and d.deptype = 'n') "
! 						  ") "
! 						  "  SELECT nsp, objid, array_agg(distinct refobjid) "
! 						  "    FROM depends "
! 						  "GROUP BY nsp, objid "
! 						  "  HAVING NOT array_agg(distinct refobjid) && array(select oid from pg_extension) "
! 						  ") "
! 						  "            ELSE true "
! 						  "        END "
! 						  "UNION ALL "
! 						  "SELECT n.tableoid, n.oid, n.nspname,  "
! 						  "(%s nspowner) AS rolname, "
! 						  "nspacl FROM pg_namespace n "
! 						  "WHERE n.nspname = 'information_schema'",
! 						  username_subquery,
! 						  username_subquery);
! 	}
! 	else
! 	{
! 		appendPQExpBuffer(query, "SELECT tableoid, oid, nspname, "
! 						  "(%s nspowner) AS rolname, "
! 						  "nspacl FROM pg_namespace",
! 						  username_subquery);
! 	}

Usually it's a lot more simple than that, as in the operator families example:

! 	if (g_fout->remoteVersion >= 90100)
! 	{
! 		appendPQExpBuffer(query, "SELECT o.tableoid, o.oid, o.opfname, "
! 						  "o.opfnamespace, "
! 						  "(%s opfowner) AS rolname "
! 						  "FROM pg_opfamily o "
! 						  "LEFT JOIN pg_depend d ON d.objid = o.oid and d.deptype = 'i' "
! 						  "and d.refclassid = 'pg_catalog.pg_extension'::pg_catalog.regclass "
! 						  "LEFT JOIN pg_extension x ON d.refobjid = x.oid "
! 						  "WHERE x.oid IS NULL",
! 						  username_subquery);
! 	}
! 	else
! 	{
! 		appendPQExpBuffer(query, "SELECT tableoid, oid, opfname, "
! 						  "opfnamespace, "
! 						  "(%s opfowner) AS rolname "
! 						  "FROM pg_opfamily",
! 						  username_subquery);
! 	}

Using the DEPENDENCY_INTERNAL implementation makes it quite simple to achieve pg_dump support.

Authoring Extension

Contrib changes

The control file

Allows to register an extension into the catalogs. Minimal meta-data and syntax support (uses recovery.conf parser), fixed expected location alongside the SQL script, pgxs support

$ cat contrib/citext/citext.control.in 
# citext
comment = 'case-insensitive character string type'
version = 'EXTVERSION'
$ grep EXT contrib/citext/Makefile
EXTENSION = $(MODULES)
EXTVERSION = $(VERSION)

Some more involved examples:

$ cat contrib/pg_stat_statements/pg_stat_statements.control.in 
# pg_stat_statements
comment = 'tracking execution statistics of all SQL statements executed'
version = 'EXTVERSION'
custom_variable_classes = 'pg_stat_statements'
pg_stat_statements.max = '1000'
pg_stat_statements.track = 'top'
pg_stat_statements.track_utility = 'true'
pg_stat_statements.save = 'true'
$ cat contrib/intarray/intarray.control.in 
# intarray
comment = 'one-dimensional arrays of integers: functions, operators, index support'
version = 'EXTVERSION'
script = '_int.sql'

custom_variable_classes

An extension author facility.

Code design and patch series

tracking extension objects

ObjectAddress CreateExtensionAddress;
bool create_extension = false;
bool create_extension_with_user_data = true;

cfparser

pg_execute_from_files()

placeholders

extension, the main patch

set_schema

Support patch for being able to move all extension's object into another schema easily.

  /*
+  * Generic function to change the namespace of a given object, for simple
+  * cases (won't work for tables or functions, objects which have more than 2
+  * key-attributes to use when searching for their syscache entries --- we
+  * don't want nor need to get this generic here).
+  *
+  * The AlterFooNamespace() calls just above will call a function whose job
+  * is to lookup the arguments for the generic function here.
+  *
+  * Relation must already by open, it's the responsibility of the caller to
+  * close it.
+  */
+ void
+ AlterObjectNamespace(Relation rel, int cacheId,
+ 					 Oid classId, Oid objid, Oid nspOid,
+ 					 int Anum_name, int Anum_namespace, int Anum_owner,
+ 					 AclObjectKind acl_kind,
+ 					 bool superuser_only)

So we have this supporting:

+ ALTER CONVERSION <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER OPERATOR CLASS <replaceable>name</replaceable> USING <replaceable class="parameter">index_method</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER OPERATOR <replaceable>name</replaceable> ( { <replaceable>left_type</replaceable> | NONE } , { <replaceable>right_type</replaceable> | NONE } ) SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER OPERATOR FAMILY <replaceable>name</replaceable> USING <replaceable class="parameter">index_method</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER TEXT SEARCH CONFIGURATION <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER TEXT SEARCH DICTIONARY <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER TEXT SEARCH PARSER <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
+ ALTER TEXT SEARCH TEMPLATE <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>

alter extension

Starting from the previous support, we now are able to have ALTER EXTENSION citext SET SCHEMA utils;

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