Oracle FDW利用外部数据库的最佳实践（oracle_fdw）

Oracle FDW: Best Practices for Leveraging External Databases

Oracle Foreign Data Wrapper (FDW) is a powerful tool that allows users to access remote Oracle databases directly from PostgreSQL. This feature is especially useful for organizations that have large amounts of data stored in different databases that need to be combined and analyzed. In this article, we will explore some best practices for using Oracle FDW to ensure the best performance and accuracy.

1. Understanding FDW

Foreign Data Wrappers are a PostgreSQL concept that allows PostgreSQL to access data residing in external databases of different types, such as Oracle, MySQL, or MS SQL. The Oracle FDW provides a direct link between PostgreSQL and remote Oracle databases, allowing users to query and access data in real-time. This link works by defining a foreign server object in PostgreSQL and creating a corresponding user mapping for each PostgreSQL user that will access the remote database.

Example:

CREATE SERVER my_oracle FOREIGN DATA WRAPPER oracle_fdw 
OPTIONS (dbserver '//remote-server:1521/xe');

CREATE USER MAPPING FOR postgres SERVER my_oracle 
OPTIONS (user 'remote-user', password 'remote-pass');

2. Tune Connection Settings

The performance of FDW queries is largely dependent on the connection settings defined in PostgreSQL. These settings include the statement_timeout, the client_encoding, the binary_as_text, and the fetch_size. The statement_timeout controls the amount of time that queries will wt for a response before timing out, while the client_encoding determines the character set used by the connection. The binary_as_text option controls how binary data is treated, and the fetch_size determines the number of rows that are returned per query.

Setting these parameters correctly can have a significant impact on query performance:

SET statement_timeout = '300s';
SET client_encoding = 'UTF8';
SET binary_as_text = 'off';
SET fetch_size = '5000';

3. Use Schemas

It’s a good practice to create a separate schema for FDW objects, as it helps to organize and manage the different functions and tables used in the queries, as well as providing better security. The schema can be created using the following command:

CREATE SCHEMA oracle_fdw AUTHORIZATION postgres;

4. Use Materialized Views

Materialized views can be created in PostgreSQL to improve the performance of FDW queries. These views store the results of selected queries and can be updated manually or automatically when necessary. Materialized views can be created using the following command:

CREATE MATERIALIZED VIEW oracle_fdw_customers
AS SELECT id, name, address FROM oracle_fdw.customers;

5. Test and Benchmark

Finally, it’s important to perform thorough testing and benchmarking to ensure that the FDW queries are providing the expected results and that the performance is satisfactory. This can be done using PostgreSQL’s built-in benchmarking tools, such as pgbench or sysbench.

To conclude, the Oracle FDW is a powerful tool that can provide significant benefits to organizations that need to access data stored in different databases. By following these best practices, users can ensure that their FDW queries are optimized for the best performance and accuracy, making it easier to combine and analyze data from multiple sources.