Added support for database index migrations.

Author: bittercoder

Migrator-vs2008.sln

@@ -503,5 +503,28 @@ void GenerateForeignKey(string foreignTable, string foreignColumn, string primar
 		/// <param name="guid"></param>
 		/// <returns></returns>
 		string Encode(Guid guid);
+
+        /// <summary>
+		/// Add a multi-column index to a table
+		/// </summary>
+		/// <param name="name">The name of the index to add.</param>
+		/// <param name="table">The name of the table that will get the index.</param>
+		/// <param name="columns">The name of the column or columns that are in the index.</param>
+		void AddIndex(string name, string table, params string[] columns);
+        
+        /// <summary>
+		/// Check to see if an index exists
+		/// </summary>
+		/// <param name="name">The name of the index</param>
+		/// <param name="table">The table that the index lives on.</param>
+		/// <returns></returns>
+		bool IndexExists(string table, string name);
+
+        /// <summary>
+		/// Remove an existing index
+		/// </summary>
+		/// <param name="table">The table that contains the index.</param>
+		/// <param name="name">The name of the index to remove</param>
+		void RemoveIndex(string table, string name);
 	}
 }

src/Migrator.Framework/ITransformationProvider.cs

@@ -160,5 +160,18 @@ public override void RenameColumn(string tableName, string oldColumnName, string
 				}
 			}
 		}
+
+        public override void RemoveIndex(string table, string name)
+		{
+			if (IndexExists(table, name))
+			{
+				ExecuteNonQuery(String.Format("DROP INDEX {1} ON {0}", table, _dialect.Quote(name)));
+			}
+		}
+
+        public override bool IndexExists(string table, string name)
+		{
+			return ConstraintExists(table, name);
+		}
 	}
 }

src/Migrator.Providers/Impl/Mysql/MySqlTransformationProvider.cs

@@ -324,5 +324,16 @@ public override string Encode(Guid guid)
 			foreach (byte b in bytes) hex.AppendFormat("{0:X2}", b);
 			return hex.ToString();
 		}
+
+        public override bool IndexExists(string table, string name)
+		{
+			string sql =
+				string.Format(
+					"SELECT COUNT(index_name) FROM user_indexes WHERE lower(index_name) = '{0}' AND lower(table_name) = '{1}'",
+					name.ToLower(), table.ToLower());
+			Logger.Log(sql);
+			object scalar = ExecuteScalar(sql);
+			return Convert.ToInt32(scalar) == 1;
+		}
 	}
 }

src/Migrator.Providers/Impl/Oracle/OracleTransformationProvider.cs

@@ -132,5 +132,14 @@ public override Column GetColumnByName(string table, string columnName)
 			// Duplicate because of the lower case issue
 			return Array.Find(GetColumns(table), column => column.Name == columnName.ToLower());
 		}
+
+        public override bool IndexExists(string table, string name)
+        {
+            using (IDataReader reader =
+                ExecuteQuery(string.Format("SELECT indexname FROM pg_catalog.pg_indexes WHERE indexname = lower('{0}')", name)))
+            {
+                return reader.Read();
+            }
+        }
 	}
 }

src/Migrator.Providers/Impl/PostgreSQL/PostgreSQLTransformationProvider.cs

@@ -235,5 +235,14 @@ public bool ColumnMatch(string column, string columnDef)
 		{
 			return columnDef.StartsWith(column + " ") || columnDef.StartsWith(_dialect.Quote(column));
 		}
+
+        public override bool IndexExists(string table, string name)
+		{
+			using (IDataReader reader =
+				ExecuteQuery(String.Format("SELECT name FROM sqlite_master WHERE type='index' and name='{0}'", name)))
+			{
+				return reader.Read();
+			}
+		}
 	}
 }

src/Migrator.Providers/Impl/SQLite/SQLiteTransformationProvider.cs

@@ -157,5 +157,24 @@ INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC
 				+ "AND col.name = '{1}' AND col.id = object_id('{0}')",
 				table, column);*/
 		}
+
+        public override bool IndexExists(string table, string name)
+		{
+			using (IDataReader reader =
+				ExecuteQuery(string.Format("SELECT top 1 * FROM sys.indexes WHERE object_id = OBJECT_ID('{0}') AND name = '{1}'", table, name)))
+			{
+				return reader.Read();
+			}
+		}
+
+        public override void RemoveIndex(string table, string name)
+		{
+			if (TableExists(table) && IndexExists(table, name))
+			{
+				table = _dialect.TableNameNeedsQuote ? _dialect.Quote(table) : table;
+				name = _dialect.ConstraintNameNeedsQuote ? _dialect.Quote(name) : name;
+				ExecuteNonQuery(String.Format("DROP INDEX {0} ON {1}", name, table));
+			}
+		}
 	}
 }

src/Migrator.Providers/Impl/SqlServer/SqlServerTransformationProvider.cs

@@ -355,5 +355,20 @@ public int Insert(string table, string[] columns, string[] columnValues)
 		protected void CreateSchemaInfoTable()
 		{
 		}
+
+        public void RemoveIndex(string table, string name)
+		{
+			// No Op
+		}
+
+        public void AddIndex(string name, string table, params string[] columns)
+		{
+			// No Op
+		}
+
+        public bool IndexExists(string table, string name)
+		{
+			return false;
+		}
 	}
 }

src/Migrator.Providers/NoOpTransformationProvider.cs

@@ -1036,5 +1036,26 @@ void QuoteColumnNames(string[] primaryColumns)
 				primaryColumns[i] = QuoteColumnNameIfRequired(primaryColumns[i]);
 			}
 		}
+
+        public virtual void RemoveIndex(string table, string name)
+		{
+			if (TableExists(table) && IndexExists(table, name))
+			{
+				name = _dialect.ConstraintNameNeedsQuote ? _dialect.Quote(name) : name;
+				ExecuteNonQuery(String.Format("DROP INDEX {0}", name));
+			}
+		}
+
+        public virtual void AddIndex(string name, string table, params string[] columns)
+		{
+			if (IndexExists(table, name))
+			{
+				Logger.Warn("Index {0} already exists", name);
+				return;
+			}
+			ExecuteNonQuery(String.Format("CREATE INDEX {0} ON {1} ({2}) ", name, table, string.Join(", ", columns)));
+		}
+
+        public abstract bool IndexExists(string table, string name);
 	}
 }

src/Migrator.Providers/TransformationProvider.cs

@@ -26,5 +26,10 @@ public override bool ConstraintExists(string table, string name)
 		{
 			return false;
 		}
+
+        public override bool IndexExists(string table, string name)
+		{
+			return false;
+		}
 	}
 }