Despite of the fact that PostgreSQL is known as extremely robust and powerful RDBMS, many organizations ranged from small businesses to world biggest corporations such as Uber migrate their databases from PostgreSQL to MySQL. Some weaknesses of PostgreSQL are the key reasons for migration: poor supportof multiversion concurrency control (MVCC), issues on upgrading to newer releases, too complicated support and development of the database and others. Below a few of the most important PostgreSQL bottlenecks are considered in details.
PostgreSQL’s approach to replica MVCC support may poses a challenge. Unlike true replica MVCC support, where replicas maintain a copy of on-disk data identical to the master, PostgreSQL requires replicas to maintain old row versions for MVCC.
When a streaming replica has an open transaction, updates to the database that affect rows held open by the transaction are blocked. This causes the WAL application thread in PostgreSQL to pause until the transaction is completed. This can result in significant lag between the master and the replica, especially if the transaction takes a long time. To address this, PostgreSQL implements a timeout mechanism. If a transaction blocks the WAL application for a specific duration, PostgreSQL terminates that transaction.
This design characteristic of PostgreSQL can lead to routine lag of seconds between replicas and the master, making it easier to unintentionally write code that results in killed transactions. Application developers, especially those who are not database experts and rely on ORMs that abstract low-level details, may not be aware of this issue. For example, if a developer has code that sends an email receipt to a user, the code may implicitly have a database transaction that remains open until the email is sent. While it’s generally considered best practice to avoid keeping database transactions open during unrelated blocking I/O operations, developers may not always be aware of this, leading to potential problems.
It is crucial for developers to understand the implications of PostgreSQL’s replica MVCC support and its impact on transaction handling. By being aware of the potential issues and ensuring proper transaction management, developers can avoid unintended consequences and maintain the desired performance and data integrity in their applications.
How to Convert PostgreSQL Database to MySQL
PostgreSQL and MySQL have differences in SQL syntax, features, and behavior, which may require careful attention during the migration process. Complex queries, stored procedures, and functions in PostgreSQL may require significant modifications to work correctly in MySQL. Therefore, thorough planning and testing are recommended to ensure a successful migration from PostgreSQL to MySQL.
There are some special tools that can help with such steps of the project as schema migration, types mapping, conversion of indexes,constraints and views, and data migration. One of this software tools is PostgreSQL to MySQL converter. It uses low-level algorithms ofreading and writing the data (without ODBC or any other middleware) to ensure the high performance of the migration. The benchmarks show about 50000 rows per second on medium P5 two-cores system. Other features of PostgreSQL to MySQL converter:
- Works with all modern versions of on-premises and could MySQL and PostgreSQL
- Tables, types, data, indexes and constraints are converted
- Command line support enable scripting and scheduling the database conversion
- SSL connection for PostgreSQL is supported
- Provides option to export PostgreSQL database into MySQL script file
- Allows filtering PostgreSQL data to migrate through SELECT-queries
- Provides option to merge or synchronize existing MySQL tables with PostgreSQL data
Visit the official site of Intelligent Converters to learn more about PostgreSQL to MySQL converter.