• Add support for configuring migration strategy on a per-adapter basis.

  migration_strategy can now be set on individual adapter classes, overriding the global ActiveRecord.migration_strategy. This allows individual databases to customize migration execution logic:

  class CustomPostgresStrategy < ActiveRecord::Migration::DefaultStrategy
    def drop_table(*)
      # Custom logic specific to PostgreSQL
    end
  end
  
  ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.migration_strategy = CustomPostgresStrategy

  Adrianna Chang

• Allow either explain format syntax for EXPLAIN queries.

  MySQL uses FORMAT=JSON whereas Postgres uses FORMAT JSON. We should be able to accept both formats as options.

  Gannon McGibbon

• On MySQL parallel test database table reset to use DELETE instead of TRUNCATE.

  Truncating on MySQL is very slow even on empty or nearly empty tables.

  As a result of this change auto increment counters are now no longer reset between test runs on MySQL and the SKIP_TEST_DATABASE_TRUNCATE environment variable no longer has any effect.

  Donal McBreen

• Fix inconsistency in PostgreSQL handling of unbounded time range types

  Use -infinity rather than NULL for the lower value of PostgreSQL time ranges when saving records with a Ruby range that begins with nil.

  create_table :products do |t|
    t.tsrange :period
  end
  class Product < ActiveRecord::Base; end
  
  t = Time.utc(2000)
  
  Product.create(period: t...nil)
  Product.create(period: nil...t)

  Previously this would create two records using different values to represent lower-unbounded and upper-unbounded ranges.

  ["2000-01-01 00:00:00",infinity)
  (NULL,"2000-01-01 00:00:00")

  Now both will use -infinity/infinity which are handled differently than NULL by some PostgreSQL range operators (e.g., lower_inf) and support both exclusive and inclusive bounds.

  ["2000-01-01 00:00:00",infinity)
  [-infinity,"2000-01-01 00:00:00")

  Martin-Alexander

• Database-specific shard swap prohibition

  In #43485 (v7.0.0), shard swapping prohibition was introduced as a global switch that applied to all databases.

  For the use case of a multi-database application, the global prohibition is overly broad, and so with this change the method prohibit_shard_swapping will scope the prohibition to the same connection class (i.e., connection_specification_name). This allows an application to prohibit shard swapping on a specific database while allowing it on all others.

  Mike Dalessio

• Fix upsert_all when using repeated timestamp attributes.

  Gannon McGibbon

• PostgreSQL enable drop database FORCE option.

  One of the benefits of developing with MySQL is that it allows dropping the current database without first disconnecting clients. As a result developers can use bin/rails db:reset and similar, without first shutting down instances of the app, Rails consoles, background workers, etc. By default PostgreSQL fails to drop a database when clients are connected and displays the following error:

  PG::ObjectInUse: ERROR: database "xyz" is being accessed by other users (PG::ObjectInUse)

  This is frustrating when working in development where the database may be dropped frequently.

  PostgreSQL 13 added the FORCE option to the DROP DATABASE statement (PostgreSQL docs) which automatically disconnects clients before dropping the database. This option is automatically enabled for supported PostgreSQL versions.

  Steven Webb

• Raise specific exception when a prohibited shard change is attempted.

  The new ShardSwapProhibitedError exception allows applications and connection-related libraries to more easily recover from this specific scenario. Previously an ArgumentError was raised, so the new exception subclasses ArgumentError for backwards compatibility.

  Mike Dalessio

• Fix SQLite3 data loss during table alterations with CASCADE foreign keys.

  When altering a table in SQLite3 that is referenced by child tables with ON DELETE CASCADE foreign keys, ActiveRecord would silently delete all data from the child tables. This occurred because SQLite requires table recreation for schema changes, and during this process the original table is temporarily dropped, triggering CASCADE deletes on child tables.

  The root cause was incorrect ordering of operations. The original code wrapped disable_referential_integrity inside a transaction, but PRAGMA foreign_keys cannot be modified inside a transaction in SQLite - attempting to do so simply has no effect. This meant foreign keys remained enabled during table recreation, causing CASCADE deletes to fire.

  The fix reverses the order to follow the official SQLite 12-step ALTER TABLE procedure: disable_referential_integrity now wraps the transaction instead of being wrapped by it. This ensures foreign keys are properly disabled before the transaction starts and re-enabled after it commits, preventing CASCADE deletes while maintaining data integrity through atomic transactions.

  Ruy Rocha

• Fix negative scopes for enums to include records with nil values.

  fatkodima

• Improve support for SQLite database URIs.

  The db:create and db:drop tasks now correctly handle SQLite database URIs, and the SQLite3Adapter will create the parent directory if it does not exist.

  Mike Dalessio

Please check [8-1-stable]) for previous changes.