OrmLite 能否识别我的 POCO 和我的架构之间的差异，并根据需要自动添加（或删除）列以强制架构与我的 POCO 保持同步？
如果这种能力不存在，我有没有办法在数据库中查询表模式，以便我可以手动执行同步？我找到了this，但我使用的是随 ServiceStack 一起安装的 OrmLite 版本，并且在我的一生中，我找不到具有 TableInfo 类的命名空间。
【问题讨论】：
标签： servicestack ormlite-servicestack
我创建了一个扩展方法来自动将缺失的列添加到我的表中。到目前为止工作得很好。警告：获取列名的代码是特定于 SQL Server 的。
namespace System.Data
{
public static class IDbConnectionExtensions
{
private static List<string> GetColumnNames(IDbConnection db, string tableName)
{
var columns = new List<string>();
using (var cmd = db.CreateCommand())
{
cmd.CommandText = "exec sp_columns " + tableName;
var reader = cmd.ExecuteReader();
while (reader.Read())
{
var ordinal = reader.GetOrdinal("COLUMN_NAME");
columns.Add(reader.GetString(ordinal));
}
reader.Close();
}
return columns;
}
public static void AlterTable<T>(this IDbConnection db) where T : new()
{
var model = ModelDefinition<T>.Definition;
// just create the table if it doesn't already exist
if (db.TableExists(model.ModelName) == false)
{
db.CreateTable<T>(overwrite: false);
return;
}
// find each of the missing fields
var columns = GetColumnNames(db, model.ModelName);
var missing = ModelDefinition<T>.Definition.FieldDefinitions
.Where(field => columns.Contains(field.FieldName) == false)
.ToList();
// add a new column for each missing field
foreach (var field in missing)
{
var alterSql = string.Format("ALTER TABLE {0} ADD {1} {2}",
model.ModelName,
field.FieldName,
db.GetDialectProvider().GetColumnTypeDefinition(field.FieldType)
);
Console.WriteLine(alterSql);
db.ExecuteSql(alterSql);
}
}
}
}
【讨论】：
db.GetDialectProvider().GetColumnTypeDefinition(field.FieldType) 在这里，您将获得该类型的默认值。类型可能具有[StringLength(50)] 之类的属性，因此如果您不想错过它们，您应该检查属性及其值以在 DB 中设置正确的类型。
var alterSql = db.GetDialectProvider().ToAddColumnStatement(typeof(T), field); 这考虑了字符串长度、nvarchar 等.
不，ServiceStack's OrmLite 中目前不支持自动迁移 RDBMS Schema 与 POCO。
OrmLite's issues 目前正在讨论一些线程，它们正在探索添加此内容的不同方法。
【讨论】：
这里是 cornelha 的代码稍作修改的版本，可用于 PostgreSQL。删除了这个片段
//private static List<string> GetColumnNames(object poco)
//{
// var list = new List<string>();
// foreach (var prop in poco.GetType().GetProperties())
// {
// list.Add(prop.Name);
// }
// return list;
//}
并使用IOrmLiteDialectProvider.NamingStrategy.GetTableName 和IOrmLiteDialectProvider.NamingStrategy.GetColumnName 方法将表名和列名从PascalNotation 转换为OrmLite 在PostgreSQL 中创建表时使用的this_kind_of_notation。
public static class IDbConnectionExtensions
{
private static List<string> GetColumnNames(IDbConnection db, string tableName, IOrmLiteDialectProvider provider)
{
var columns = new List<string>();
using (var cmd = db.CreateCommand())
{
cmd.CommandText = getCommandText(tableName, provider);
var tbl = new DataTable();
tbl.Load(cmd.ExecuteReader());
for (int i = 0; i < tbl.Columns.Count; i++)
{
columns.Add(tbl.Columns[i].ColumnName);
}
}
return columns;
}
private static string getCommandText(string tableName, IOrmLiteDialectProvider provider)
{
if (provider == PostgreSqlDialect.Provider)
return string.Format("select * from {0} limit 1", tableName);
else return string.Format("select top 1 * from {0}", tableName);
}
public static void AlterTable<T>(this IDbConnection db, IOrmLiteDialectProvider provider) where T : new()
{
var model = ModelDefinition<T>.Definition;
var table = new T();
var namingStrategy = provider.NamingStrategy;
// just create the table if it doesn't already exist
var tableName = namingStrategy.GetTableName(model.ModelName);
if (db.TableExists(tableName) == false)
{
db.CreateTable<T>(overwrite: false);
return;
}
// find each of the missing fields
var columns = GetColumnNames(db, model.ModelName, provider);
var missing = ModelDefinition<T>.Definition.FieldDefinitions
.Where(field => columns.Contains(namingStrategy.GetColumnName(field.FieldName)) == false)
.ToList();
// add a new column for each missing field
foreach (var field in missing)
{
var columnName = namingStrategy.GetColumnName(field.FieldName);
var alterSql = string.Format("ALTER TABLE {0} ADD COLUMN {1} {2}",
tableName,
columnName,
db.GetDialectProvider().GetColumnTypeDefinition(field.FieldType)
);
Console.WriteLine(alterSql);
db.ExecuteSql(alterSql);
}
}
}
【讨论】：
我实现了一个 UpdateTable 函数。基本思路是：
Github 仓库：https://github.com/peheje/Extending-NServiceKit.OrmLite
精简代码：
public interface ISqlProvider
{
string RenameTableSql(string currentName, string newName);
string GetColumnNamesSql(string tableName);
string InsertIntoSql(string intoTableName, string fromTableName, string commaSeparatedColumns);
string DropTableSql(string tableName);
}
public static void UpdateTable<T>(IDbConnection connection, ISqlProvider sqlProvider) where T : new()
{
connection.CreateTableIfNotExists<T>();
var model = ModelDefinition<T>.Definition;
string tableName = model.Name;
string tableNameTmp = tableName + "Tmp";
string renameTableSql = sqlProvider.RenameTableSql(tableName, tableNameTmp);
connection.ExecuteNonQuery(renameTableSql);
connection.CreateTable<T>();
string getModelColumnsSql = sqlProvider.GetColumnNamesSql(tableName);
var modelColumns = connection.SqlList<string>(getModelColumnsSql);
string getDbColumnsSql = sqlProvider.GetColumnNamesSql(tableNameTmp);
var dbColumns = connection.SqlList<string>(getDbColumnsSql);
List<string> activeFields = dbColumns.Where(dbColumn => modelColumns.Contains(dbColumn)).ToList();
string activeFieldsCommaSep = ListToCommaSeparatedString(activeFields);
string insertIntoSql = sqlProvider.InsertIntoSql(tableName, tableNameTmp, activeFieldsCommaSep);
connection.ExecuteSql(insertIntoSql);
string dropTableSql = sqlProvider.DropTableSql(tableNameTmp);
//connection.ExecuteSql(dropTableSql); //maybe you want to clean up yourself, else uncomment
}
private static String ListToCommaSeparatedString(List<String> source)
{
var sb = new StringBuilder();
for (int i = 0; i < source.Count; i++)
{
sb.Append(source[i]);
if (i < source.Count - 1)
{
sb.Append(", ");
}
}
return sb.ToString();
}
}
MySql 实现：
public class MySqlProvider : ISqlProvider
{
public string RenameTableSql(string currentName, string newName)
{
return "RENAME TABLE `" + currentName + "` TO `" + newName + "`;";
}
public string GetColumnNamesSql(string tableName)
{
return "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '" + tableName + "';";
}
public string InsertIntoSql(string intoTableName, string fromTableName, string commaSeparatedColumns)
{
return "INSERT INTO `" + intoTableName + "` (" + commaSeparatedColumns + ") SELECT " + commaSeparatedColumns + " FROM `" + fromTableName + "`;";
}
public string DropTableSql(string tableName)
{
return "DROP TABLE `" + tableName + "`;";
}
}
用法：
using (var db = dbFactory.OpenDbConnection())
{
DbUpdate.UpdateTable<SimpleData>(db, new MySqlProvider());
}
尚未使用 FK 进行测试。无法处理重命名属性。
【讨论】：
我需要实现类似的东西，发现 Scott 的帖子很有帮助。我决定做一个小改动，让它变得更加不可知。由于我只使用 Sqlite 和 MSSQL，所以我把 getCommand 方法做得很简单，但可以扩展。我使用了一个简单的数据表来获取列。此解决方案非常适合我的要求。
public static class IDbConnectionExtensions
{
private static List<string> GetColumnNames(IDbConnection db, string tableName,IOrmLiteDialectProvider provider)
{
var columns = new List<string>();
using (var cmd = db.CreateCommand())
{
cmd.CommandText = getCommandText(tableName, provider);
var tbl = new DataTable();
tbl.Load(cmd.ExecuteReader());
for (int i = 0; i < tbl.Columns.Count; i++)
{
columns.Add(tbl.Columns[i].ColumnName);
}
}
return columns;
}
private static string getCommandText(string tableName, IOrmLiteDialectProvider provider)
{
if(provider == SqliteDialect.Provider)
return string.Format("select * from {0} limit 1", tableName);
else return string.Format("select top 1 * from {0}", tableName);
}
private static List<string> GetColumnNames(object poco)
{
var list = new List<string>();
foreach (var prop in poco.GetType().GetProperties())
{
list.Add(prop.Name);
}
return list;
}
public static void AlterTable<T>(this IDbConnection db, IOrmLiteDialectProvider provider) where T : new()
{
var model = ModelDefinition<T>.Definition;
var table = new T();
// just create the table if it doesn't already exist
if (db.TableExists(model.ModelName) == false)
{
db.CreateTable<T>(overwrite: false);
return;
}
// find each of the missing fields
var columns = GetColumnNames(db, model.ModelName,provider);
var missing = ModelDefinition<T>.Definition.FieldDefinitions
.Where(field => columns.Contains(field.FieldName) == false)
.ToList();
// add a new column for each missing field
foreach (var field in missing)
{
var alterSql = string.Format("ALTER TABLE {0} ADD {1} {2}",
model.ModelName,
field.FieldName,
db.GetDialectProvider().GetColumnTypeDefinition(field.FieldType)
);
Console.WriteLine(alterSql);
db.ExecuteSql(alterSql);
}
}
}
【讨论】：
所以我接受了 user44 的回答，并修改了 AlterTable 方法以使其更有效率。 我没有为每个字段/列循环和运行一个 SQL 查询，而是通过一些简单的文本解析（MySQL 命令！）将其合并为一个。
public static void AlterTable<T>(this IDbConnection db, IOrmLiteDialectProvider provider) where T : new()
{
var model = ModelDefinition<T>.Definition;
var table = new T();
var namingStrategy = provider.NamingStrategy;
// just create the table if it doesn't already exist
var tableName = namingStrategy.GetTableName(model.ModelName);
if (db.TableExists(tableName) == false)
{
db.CreateTable<T>(overwrite: false);
return;
}
// find each of the missing fields
var columns = GetColumnNames(db, model.ModelName, provider);
var missing = ModelDefinition<T>.Definition.FieldDefinitions
.Where(field => columns.Contains(namingStrategy.GetColumnName(field.FieldName)) == false)
.ToList();
string alterSql = "";
string addSql = "";
// add a new column for each missing field
foreach (var field in missing)
{
var alt = db.GetDialectProvider().ToAddColumnStatement(typeof(T), field); // Should be made more efficient, one query for all changes instead of many
int index = alt.IndexOf("ADD ");
alterSql = alt.Substring(0, index);
addSql += alt.Substring(alt.IndexOf("ADD COLUMN")).Replace(";", "") + ", ";
}
if (addSql.Length > 2)
addSql = addSql.Substring(0, addSql.Length - 2);
string fullSql = alterSql + addSql;
Console.WriteLine(fullSql);
db.ExecuteSql(fullSql);
}【讨论】：