Documentation

The default strategy. The index will be added as part of a database transaction along with all the other DDL being executed to migrate the database schema. If any migration should fail, the index creation will be rolled back as part of the transaction. This is how schema migrations work in general in Orville.

Creates the index using the CONCURRENTLY keyword in PostgreSQL. Index creation will not lock the table during creation, allowing the application to access the table normally while the index is created. Concurrent index creation cannot be done in a transaction, so indexes created using CONCURRENTLY are created outside the normal schema transaction. Index creation may fail when using the Concurrent strategy. Orville has no special provision to detect or recover from this failure currently. You should manually check that index creation has succeeded. If necessary, you can manually drop the index to cause Orville to recreate it the next time migrations are run. Note that while the table will not be locked, index migration will still block application startup by default. See the information about schema migration options in Orville.PostgreSQL.AutoMigration for details about how to work around this if it is a problem for you. Also, it a good idea to read the PostgreSQL docs about creating indexes concurrently before you use this strategy. See https://www.postgresql.org/docs/current/sql-createindex.html#SQL-CREATEINDEX-CONCURRENTLY.