Laurenz Albe performs a comparison:
The transaction system is a core component of a relational database. It provides services that facilitate developing applications that guarantee data integrity. The SQL standard regulates some of the features of database transactions, but leaves many details unspecified. As a consequence, the transaction systems of relational databases can differ substantially. These days, many people are trying to get away from Oracle database and move to PostgreSQL. To migrate an application from Oracle to PostgreSQL, it is crucial to understand the differences between the respective transaction systems. Otherwise, you can end up with nasty surprises that may jeopardize performance and data integrity. So I thought it would be useful to compile a comparison of the features of transactions in Oracle and PostgreSQL.
Read on for that dive into how the two products compare.