prepare-execute-and-deallocate-statements.md

Prepare, Execute, and Deallocate Statements

In PostgreSQL, you can prepare a named statement to be executed later using prepare.

> prepare column_names (text) as
    select column_name from information_schema.columns where table_name = $1;
PREPARE

These statements are kept around for the duration of the session. To see the available statements, check out the pg_prepared_statements view.

> select * from pg_prepared_statements;
     name     |                                  statement                                  |         prepare_time          | parameter_types | from_sql
--------------+-----------------------------------------------------------------------------+-------------------------------+-----------------+----------
 column_names | prepare column_names (text) as                                             +| 2017-03-10 15:01:09.154528-06 | {text}          | t
              |   select column_name from information_schema.columns where table_name = $1; |                               |                 |

To run a prepared statement, use execute with the name of the statement and any arguments.

> execute column_names('users');
   column_name
-----------------
 id
 email
 password_digest
 created_at
 updated_at
 first_name
 last_name

You can also delete a statement with deallocate if you'd like.

> deallocate column_names;
DEALLOCATE