defaults

func UsesFastPath ¶

func UsesFastPath(ctx context.Context, conn db.DB, tableName, columnType, defaultExpr string) (bool, error)

UsesFastPath returns true if [defaultExpr] will use the fast-path optimization added in Postgres 11 to avoid taking an `ACCESS_EXCLUSIVE` lock when adding a new column with a `DEFAULT` value.

The implementation works by creating a schema-only copy of [tableName], adding a new column with a `DEFAULT` value of [defaultExpr] and checking system catalogs to see if the fast-path optimization was applied.