An introduction to Postgres 🐘 Prepared Statements

In the realm of database management, optimizing query performance is a crucial aspect of ensuring the efficiency of applications. Postgres, a robust open-source relational database, offers a powerful feature known as "Prepared Statements" to enhance the execution of SQL queries. In this blog post, we'll delve into the concept of Postgres Prepared Statements, exploring their application in tables and composite types, providing sample SQL code, and elucidating the syntax for creating these statements. Additionally, we'll highlight the merits of leveraging Prepared Statements in your database interactions.
The syntax for creating Prepared Statements in Postgres involves two primary commands: PREPARE and EXECUTE.

PREPARE statement_name [ (data_type [, ...]) ] AS
    SQL_query_string;

EXECUTE statement_name [ (parameter [, ...]) ];

Let us explore the concept with both tables and composite types.
(a) In Tables
Prepared Statements in Postgres allow for the precompilation and reuse of SQL queries. In the context of tables, this translates to improved performance by reducing the overhead of parsing and planning queries for repetitive executions. Prepared Statements can be especially beneficial when dealing with frequently executed queries involving tables.

Example 1: Prepared Statement for Selecting Data from a Table

PREPARE select_employee (INT) AS
    SELECT * FROM employees WHERE employee_id = $1;

EXECUTE select_employee(1001);

(b) In Composite Types
Beyond tables, Prepared Statements extend their utility to composite types. Composite types in Postgres enable the grouping of related fields into a single user-defined type. Leveraging Prepared Statements in conjunction with composite types enhances code modularity and readability, making it easier to manage complex data structures.

Example 1: Prepared Statement for Selecting Data from a Table

CREATE TYPE person_type AS (
    name VARCHAR,
    age INT
);

PREPARE insert_person (person_type) AS
    INSERT INTO people VALUES ($1);

EXECUTE insert_person(ROW('John Doe', 30));

Why Use Prepared Statements?

1. Performance Optimization: Prepared Statements reduce query processing overhead by preparing and planning queries only once, resulting in faster execution for repeated queries.
2. Parameterized Queries: Prepared Statements support parameterized queries, allowing for dynamic data input. This not only enhances security by preventing SQL injection but also promotes code reusability.
3. Execution Plan Reuse: Postgres caches the execution plan of a Prepared Statement, allowing the database engine to reuse the plan for subsequent executions, further contributing to performance gains.
4. Reduced Network Traffic: Parameter values are sent separately from the query, minimizing network traffic, which is especially beneficial in scenarios with frequent query executions.