## Appendix F. Additional Supplied Modules

This appendix and the next one contain information regarding the modules that can be found in the `contrib` directory of the PostgreSQL distribution. These include 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.

This appendix covers extensions and other server plug-in modules found in `contrib`. Appendix G covers utility programs.

When building from the source distribution, these components are not built automatically, unless you build the "world" target (see Step 2). You can build and install all of them by running:

    make
    make install

in the `contrib` directory of a configured source tree; or to build and install just one selected module, do the same in that module's subdirectory. Many of the modules have regression tests, which can be executed by running:

    make check

before installation or

    make installcheck

once you have a PostgreSQL server running.

If you are using a pre-packaged version of PostgreSQL, these modules are typically made available as a separate subpackage, such as `postgresql-contrib`.

Many modules 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. In PostgreSQL 9.1 and later, this is done by executing a CREATE EXTENSION command. In a fresh database, you can simply do

    CREATE EXTENSION module_name;

This command must be run by a database superuser. This registers the new SQL objects in the current database only, so you need to run this command in each database that you want the module's facilities to be available in. Alternatively, run it in database `template1` so that the extension will be copied into subsequently-created databases by default.

Many modules allow you to install their objects in a schema of your choice. To do that, add `SCHEMA `schema_name`` to the `CREATE EXTENSION` command. By default, the objects will be placed in your current creation target schema, typically `public`.

If your database was brought forward by dump and reload from a pre-9.1 version of PostgreSQL, and you had been using the pre-9.1 version of the module in it, you should instead do

    CREATE EXTENSION module_name FROM unpackaged;

This will update the pre-9.1 objects of the module into a proper extension object. Future updates to the module will be managed by ALTER EXTENSION. For more information about extension updates, see Section 36.15.

Note, however, that some of these modules are not “extensions” in this sense, but are loaded into the server in some other way, for instance by way of shared_preload_libraries. See the documentation of each module for details.

## F.1. adminpack

`adminpack` provides a number of support functions which pgAdmin and other administration and management tools can use to provide additional functionality, such as remote management of server log files. Use of all these functions is restricted to superusers.

The functions shown in Table F.1 provide write access to files on the machine hosting the server. (See also the functions in Table 9.86, which provide read-only access.) Only files within the database cluster directory can be accessed, but either a relative or absolute path is allowable.

Table F.1. `adminpack` Functions

Name | Return Type | Description
--- | --- | ---
`pg_catalog.pg_file_write(filename text, data text, append boolean)` | `bigint` | Write, or append to, a text file
`pg_catalog.pg_file_rename(oldname text, newname text [, archivename text])` | `boolean` | Rename a file
`pg_catalog.pg_file_unlink(filename text)` | `boolean` | Remove a file
`pg_catalog.pg_logdir_ls()` | `setof record` | List the log files in the `log_directory` directory

`pg_file_write` writes the specified `data` into the file named by `filename`. If `append` is false, the file must not already exist. If `append` is true, the file can already exist, and will be appended to if so. Returns the number of bytes written.

`pg_file_rename` renames a file. If `archivename` is omitted or NULL, it simply renames `oldname` to `newname` (which must not already exist). If `archivename` is provided, it first renames `newname` to `archivename` (which must not already exist), and then renames `oldname` to `newname`. In event of failure of the second rename step, it will try to rename `archivename` back to `newname` before reporting the error. Returns true on success, false if the source file(s) are not present or not writable; other cases throw errors.

`pg_file_unlink` removes the specified file. Returns true on success, false if the specified file is not present or the `unlink()` call fails; other cases throw errors.

`pg_logdir_ls` returns the start timestamps and path names of all the log files in the log_directory directory. The log_filename parameter must have its default setting (`postgresql-%Y-%m-%d_%H%M%S.log`) to use this function.

The functions shown in Table F.2 are deprecated and should not be used in new applications; instead use those shown in Table 9.77 and Table 9.86. These functions are provided in `adminpack` only for compatibility with old versions of pgAdmin.

Table F.2. Deprecated `adminpack` Functions

Name | Return Type | Description
--- | --- | ---
`pg_catalog.pg_file_read(filename text, offset bigint, nbytes bigint)` | `text` | Alternate name for `pg_read_file()`
`pg_catalog.pg_file_length(filename text)` | `bigint` | Same as `size` column returned by `pg_stat_file()`
`pg_catalog.pg_logfile_rotate()` | `integer` | Alternate name for `pg_rotate_logfile()`, but note that it returns integer 0 or 1 rather than boolean