Contents

• colnames 1.7.0
  • • Pure SQL Alternative
  • Installation
  • Dependencies
  • Copyright and License

colnames 1.7.0

This extension contains a single SQL function, colnames(), that takes a record value as its argument and returns an array of the names of the columns in that record:

try=# SELECT colnames( ROW(1, 'foo', 458.0) );
  colnames
------------
 {f1,f2,f3}

This can be useful for example in trigger functions, where one might need the column names to generate a query string.

Pure SQL Alternative

Can’t use a C extension? Fear not! PostgreSQL 9.3 and later include JSON functions get the column names directly:

try=# SELECT ARRAY( SELECT json_object_keys( row_to_json( ROW( 1, 3, 'foo' ) ) ) );
   array
------------
 {f1,f2,f3}

Installation

To build colnames, just do this:

make
make install
make installcheck

If you encounter an error such as:

"Makefile", line 8: Need an operator

You need to use GNU make, which may well be installed on your system as gmake:

gmake
gmake installcheck
gmake install

If you encounter an error such as:

make: pg_config: Command not found

Be sure that you have pg_config installed and in your path. If you used a package management system such as RPM to install PostgreSQL, be sure that the -devel package is also installed. If necessary tell the build process where to find it:

make PG_CONFIG=/path/to/pg_config
make install PG_CONFIG=/path/to/pg_config
make installcheck PG_CONFIG=/path/to/pg_config

If you encounter an error such as:

ERROR:  must be owner of database regression

You need to run the test suite using a super user, such as the default “postgres” super user:

make installcheck PGUSER=postgres

Once colnames is installed, you can add it to a database. If you’re running PostgreSQL 9.1.0 or greater, it’s a simple as connecting to a database as a super user and running:

CREATE EXTENSION colnames;

If you’ve upgraded your cluster to PostgreSQL 9.1 and already had colnames installed, you can upgrade it to a properly packaged extension with:

CREATE EXTENSION colnames FROM unpackaged;

For versions of PostgreSQL less than 9.1.0, you’ll need to run the installation script:

psql -d my_db -f /path/to/pgsql/share/contrib/colnames.sql

If you want to install colnames into a specific schema, use the PGOPTIONS environment variable to specify the schema, like so:

PGOPTIONS=--search_path=extensions psql -d my_db -f colnames.sql

Dependencies

The colnames data type has no dependencies other than PostgreSQL 8.2.0 or higher.

Copyright and License

Copyright (c) 2011-2024 Andrew Gierth and David E. Wheeler.

This module is free software; you can redistribute it and/or modify it under the PostgreSQL License.

Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.

IN NO EVENT SHALL ANDREW GIERTH AND DAVID E. WHEELER BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF ANDREW GIERTH AND DAVID E. WHEELER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

ANDREW GIERTH AND DAVID E. WHEELER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN “AS IS” BASIS, AND ANDREW GIERTH AND DAVID E. WHEELER HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.