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Exploring PostgreSQL’s Foreign Data Wrapper and Statistical Functions

Exploring PostgreSQL’s Foreign Data Wrapper and Statistical Functions

PostgreSQL, renowned for its robustness and extensibility, offers several helpful functions for both developers and database administrators alike. Among these functions,

file_fdw_handlerfile_fdw_validatorpg_stat_statementspg_stat_statements_info,

and

pg_stat_statements_reset

stand out as invaluable tools for enhancing database management and performance optimization. In today’s blog we’ll learn how to use all of these functions as well as how Navicat can help!

File Functions

PostgreSQL’s Foreign Data Wrapper (FDW) functionality allows seamless integration of external data sources into the database. The

file_fdw_handler

and

file_fdw_validator

functions are specifically designed to handle foreign tables backed by files. The

file_fdw_handler

function serves as an interface between PostgreSQL and the foreign data source, enabling the execution of SQL queries against files residing outside the database. Let’s consider an example where we want to create a foreign table named

external_data

referencing a CSV file named

data.csv:

CREATE SERVER file_server FOREIGN DATA WRAPPER file_fdw;

        CREATE FOREIGN TABLE external_data (
            id INT,
            name TEXT,
            age INT
        ) SERVER file_server OPTIONS (filename '/path/to/data.csv');

Meanwhile, the

file_fdw_validator

function ensures the integrity of the options provided when creating a foreign table. It validates if the specified file exists and is accessible. For instance:

SELECT file_fdw_validator('filename', '/path/to/data.csv');

Statistical Functions

PostgreSQL’s pg_stat_statements module provides a set of built-in functions for monitoring and analyzing query performance. Among these,

pg_stat_statementspg_stat_statements_info,

and

pg_stat_statements_reset

are indispensable for identifying bottlenecks and optimizing database performance.

pg_stat_statements

is a module that records statistics about SQL statements executed by a server. It tracks details such as execution counts, total runtime, and resource usage for each unique query. To enable

pg_stat_statements

you need to add it to the

shared_preload_libraries

configuration parameter in 

postgresql.conf:

shared_preload_libraries = 'pg_stat_statements'
SELECT * FROM pg_stat_statements;

pg_stat_statements_info 

provides additional information about the

pg_stat_statements

module, such as the version number and the last reset time. It can be queried as follows:

SELECT * FROM pg_stat_statements_info;

Finally,

pg_stat_statements_reset

resets the statistics collected by

pg_stat_statements

llowing you to start afresh with performance monitoring. Simply execute:

SELECT pg_stat_statements_reset();

Working with PostgreSQL's Built-in Functions in Navicat

We can access all of the above functions in Navicat for PostgreSQL or Navicat Premium 16 by expanding the “Functions” section in the Objects Pane:

To execute a function, simply select it from the Objects list and click the Execute Function button:

That will bring up a dialog where you can supply input parameter values:

Click the OK button to execute the function and view the results (or Cancel to abort):

PostgreSQL’s built-in functions, including

file_fdw_handlerfile_fdw_validatorpg_stat_statementspg_stat_statements_info,

and

pg_stat_statements_reset

play a pivotal role in enhancing database management and optimizing query performance. By leveraging these functions effectively, developers and administrators can streamline operations and ensure optimal utilization of PostgreSQL’s capabilities.

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