Fix migration bug with PostgreSQL 9.5

src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs

@@ -918,6 +918,32 @@ protected override void Generate(
             builder.EndCommand();
         }
 
+        protected override void Generate(CreateSequenceOperation operation, IModel model, MigrationCommandListBuilder builder)
+        {
+            Check.NotNull(operation, nameof(operation));
+            Check.NotNull(builder, nameof(builder));
+
+            if (VersionAtLeast(10, 0))
+            {
+                // "CREATE SEQUENCE name AS type" expression is supported only in PostgreSQL 10 or above.
+                // The base MigrationsSqlGenerator.Generate method generates that expression.
+                // https://github.com/aspnet/EntityFrameworkCore/blob/master/src/EFCore.Relational/Migrations/MigrationsSqlGenerator.cs#L533-L535
+                base.Generate(operation, model, builder);
+                return;
+            }
+
+            // Generate CREATE SEQUENCE without "AS" part.
+            builder
+                .Append("CREATE SEQUENCE ")
+                .Append(_sqlGenerationHelper.DelimitIdentifier(operation.Name, operation.Schema))
+                .Append(" START WITH ")
+                .Append(_typeMappingSource.GetMapping(typeof(long)).GenerateSqlLiteral(operation.StartValue));
+
+            SequenceOptions(operation, model, builder);
+            builder.AppendLine(_sqlGenerationHelper.StatementTerminator);
+            EndStatement(builder);
+        }
+
         #endregion Standard migrations
 
         #region Utilities

test/EFCore.PG.FunctionalTests/NpgsqlMigrationSqlGeneratorTest.cs

@@ -209,6 +209,7 @@ public virtual void CreateDatabaseOperation_with_tablespace()
                 Sql);
         }
 
+        [Fact]
         public override void CreateSequenceOperation_with_minValue_and_maxValue()
         {
             base.CreateSequenceOperation_with_minValue_and_maxValue();
@@ -218,12 +219,24 @@ public override void CreateSequenceOperation_with_minValue_and_maxValue()
                 Sql);
         }
 
+        [Fact]
         public override void CreateSequenceOperation_with_minValue_and_maxValue_not_long()
         {
-            // In PostgreSQL, sequence data types are always bigint.
-            // http://www.postgresql.org/docs/9.4/static/infoschema-sequences.html
+            base.CreateSequenceOperation_with_minValue_and_maxValue_not_long();
+            Assert.Equal(
+                "CREATE SEQUENCE dbo.\"EntityFrameworkHiLoSequence\" AS integer START WITH 3 INCREMENT BY 1 MINVALUE 2 MAXVALUE 816 CYCLE;" + EOL,
+                Sql);
+
+            using (TestHelpers.WithPostgresVersion(new Version(9, 5)))
+            {
+                base.CreateSequenceOperation_with_minValue_and_maxValue_not_long();
+                Assert.Equal(
+                    "CREATE SEQUENCE dbo.\"EntityFrameworkHiLoSequence\" START WITH 3 INCREMENT BY 1 MINVALUE 2 MAXVALUE 816 CYCLE;" + EOL,
+                    Sql);
+            }
         }
 
+        [Fact]
         public override void CreateSequenceOperation_without_minValue_and_maxValue()
         {
             base.CreateSequenceOperation_without_minValue_and_maxValue();
@@ -1050,6 +1063,20 @@ public void CreateSequenceOperation_with_data_type_smallint()
             Assert.StartsWith(
                 "CREATE SEQUENCE public.short_sequence AS smallint",
                 Sql);
+
+            using(TestHelpers.WithPostgresVersion(new Version(9, 5)))
+            {
+                Generate(
+                    new CreateSequenceOperation {
+                        Name = "short_sequence",
+                        Schema = "public",
+                        ClrType = typeof(short)
+                    });
+
+                Assert.StartsWith(
+                    "CREATE SEQUENCE public.short_sequence",
+                    Sql);
+            }
         }
 
         #endregion Sequence data types
@@ -1154,6 +1181,8 @@ public void FixedLength()
                          ");" + EOL, Sql);
         }
 
+        protected new NpgsqlTestHelpers TestHelpers => (NpgsqlTestHelpers)base.TestHelpers;
+
         public NpgsqlMigrationSqlGeneratorTest()
             : base(NpgsqlTestHelpers.Instance)
         {

test/EFCore.PG.FunctionalTests/TestUtilities/NpgsqlTestHelpers.cs

@@ -1,21 +1,45 @@
-using Microsoft.EntityFrameworkCore;
+using System;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
+using Xunit;
 
 namespace Npgsql.EntityFrameworkCore.PostgreSQL.TestUtilities
 {
     public class NpgsqlTestHelpers : TestHelpers
     {
-        protected NpgsqlTestHelpers()
+        Version _postgresVersion;
+
+        public class VersionScope : IDisposable
         {
+            NpgsqlTestHelpers _helpers;
+            Version _oldVersion, _newVersion;
+
+            internal VersionScope(NpgsqlTestHelpers helpers, Version version)
+            {
+                _helpers = helpers;
+                _oldVersion = helpers._postgresVersion;
+                _newVersion = helpers._postgresVersion = version;
+            }
+
+            public void Dispose()
+            {
+                Assert.Equal(_helpers._postgresVersion, _newVersion);
+                _helpers._postgresVersion = _oldVersion;
+            }
         }
 
+        public VersionScope WithPostgresVersion(Version version) => new VersionScope(this, version);
+
+        protected NpgsqlTestHelpers() {}
+
         public static NpgsqlTestHelpers Instance { get; } = new NpgsqlTestHelpers();
 
         public override IServiceCollection AddProviderServices(IServiceCollection services)
             => services.AddEntityFrameworkNpgsql();
 
         protected override void UseProviderOptions(DbContextOptionsBuilder optionsBuilder)
-            => optionsBuilder.UseNpgsql(new NpgsqlConnection("Database=DummyDatabase"));
+            => optionsBuilder.UseNpgsql(new NpgsqlConnection("Database=DummyDatabase"),
+                   options => options.SetPostgresVersion(_postgresVersion));
     }
 }