Exporting PL/pgSQL Results to CSV in PostgreSQL: Two Methods
PostgreSQL's PL/pgSQL procedural language allows for powerful database extensions. This guide details two methods for saving PL/pgSQL query results to a CSV file.
Method 1: Server-Side Export using COPY
The most efficient server-side approach utilizes PostgreSQL's COPY
command. A command like this:
COPY (SELECT * FROM foo) TO '/tmp/test.csv' WITH CSV DELIMITER ',' HEADER;
exports data from the "foo" table to a CSV file on the server. Crucially, this requires appropriate server-side permissions. Best practice involves creating a dedicated function with the SECURITY DEFINER
option to manage these permissions securely.
Method 2: Client-Side Export using COPY TO STDOUT
Alternatively, you can handle CSV export on the client-side using the COPY TO STDOUT
command within the psql
command-line client. The copy
meta-command facilitates this:
\copy (SELECT * FROM foo) TO '/tmp/test.csv' WITH CSV DELIMITER ',' HEADER
Note that copy
is a meta-command, not a standard SQL command, so a terminating semicolon (;
) is unnecessary.
Security Considerations (Server-Side):
The server-side approach necessitates careful security planning:
- Restricted File System Access: Limit the function's file system access to only the necessary directories.
- Controlled Database Access: Restrict database access to only the required tables.
- Robust Input Validation: Implement thorough checks to prevent malicious inputs.
Considerations for Client-Side Approach:
When using the client-side method:
- Language Compatibility: Ensure your application's programming language supports the necessary file handling functions.
-
Performance for Large Datasets: For large datasets, the performance of built-in functions like PHP's
pg_copy_from
andpg_copy_to
might be suboptimal. Consider alternative, more efficient methods.
The above is the detailed content of How to Export PL/pgSQL Query Results to a CSV File in PostgreSQL?. For more information, please follow other related articles on the PHP Chinese website!

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