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Migrate rows with unique constraints to Amazon RDS for PostgreSQL or Amazon Aurora PostgreSQL

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This article discusses how to handle unique constraints when migrating rows with unique constraints to Amazon RDS for PostgreSQL or Amazon Aurora PostgreSQL. It explains the different behaviors of handling null values in unique constraints across various databases like Oracle, SQL Server, IBM Db2, and PostgreSQL.

Specifically, the article covers:

  • How unique keys work in PostgreSQL
  • How null values are handled in unique keys in Oracle, SQL Server, IBM Db2, and PostgreSQL
  • Solutions to mimic the source database behavior for handling null values in unique constraints when migrating to PostgreSQL:
    • Using a function-based unique index
    • Using an array-based unique index
    • Using a unique index with a case structure
    • Using the NULLS NOT DISTINCT clause (PostgreSQL 15+)
  • A comparison summary of the solutions and the PostgreSQL versions they are supported in
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