improvement: create schema before table creation (#518)

Author: artiom

lib/migration_generator/phase.ex

@@ -13,14 +13,16 @@ defmodule AshPostgres.MigrationGenerator.Phase do
           Enum.map_join(operations, "\n", fn operation -> operation.__struct__.up(operation) end) <>
           "\nend"
       else
-        opts =
+        {pre_create, opts} =
           if schema do
-            ", prefix: \"#{schema}\""
+            {"execute(\"CREATE SCHEMA IF NOT EXISTS #{schema}\")" <> "\n\n",
+             ", prefix: \"#{schema}\""}
           else
-            ""
+            {"", ""}
           end
 
-        "create table(:#{as_atom(table)}, primary_key: false#{opts}) do\n" <>
+        pre_create <>
+          "create table(:#{as_atom(table)}, primary_key: false#{opts}) do\n" <>
           Enum.map_join(operations, "\n", fn operation -> operation.__struct__.up(operation) end) <>
           "\nend"
       end

test/migration_generator_test.exs

@@ -243,14 +243,6 @@ defmodule AshPostgres.MigrationGeneratorTest do
 
       defdomain([Post])
 
-      {:ok, _} =
-        Ecto.Adapters.SQL.query(
-          AshPostgres.TestRepo,
-          """
-          CREATE SCHEMA IF NOT EXISTS example;
-          """
-        )
-
       AshPostgres.MigrationGenerator.generate(Domain,
         snapshot_path: "test_snapshots_path",
         migration_path: "test_migration_path",
@@ -272,6 +264,9 @@ defmodule AshPostgres.MigrationGeneratorTest do
 
       file_contents = File.read!(file)
 
+      # the migration creates the schema
+      assert file_contents =~ "execute(\"CREATE SCHEMA IF NOT EXISTS example\")"
+
       # the migration creates the table
       assert file_contents =~ "create table(:posts, primary_key: false, prefix: \"example\") do"