protected virtual Expression VisitAsOfTable(AsOfTableExpression tableExpression)
{
// This method was modeled on "SqlServerQuerySqlGenerator.VisitTable".
// Where we deviate, is after printing the table name, we check if temporal constraints
// need to be applied.
Sql.Append(_sqlGenerationHelper.DelimitIdentifier(tableExpression.Name, tableExpression.Schema));
if (tableExpression.AsOfDate != null)
{
var name = TEMPORAL_PARAMETER_PREFIX + tableExpression.AsOfDate.Name;
Sql.Append($" FOR SYSTEM_TIME AS OF @{name}"); //2020-02-28T11:00:00
if (!_commandbuilder.Parameters.Any(x => x.InvariantName == tableExpression.AsOfDate.Name))
{
_commandbuilder.AddParameter(tableExpression.AsOfDate.Name, name);
}
}
Sql
.Append(AliasSeparator)
.Append(_sqlGenerationHelper.DelimitIdentifier(tableExpression.Alias));
return(tableExpression);
}
protected virtual Expression VisitAsOfTable(AsOfTableExpression tableExpression)
{
Sql.Append(_sqlGenerationHelper.DelimitIdentifier(tableExpression.Name, tableExpression.Schema));
if (tableExpression.DateParameter != null)
{
var name = "__ef_temporal" + tableExpression.DateParameter.Name;
Sql.Append($" FOR SYSTEM_TIME AS OF @{name}"); //2020-02-28T11:00:00
if (!_commandbuilder.Parameters.Any(x => x.InvariantName == tableExpression.DateParameter.Name))
{
_commandbuilder.AddParameter(tableExpression.DateParameter.Name, name);
}
}
Sql
.Append(AliasSeparator)
.Append(_sqlGenerationHelper.DelimitIdentifier(tableExpression.Alias));
return(tableExpression);
}
public override SelectExpression Select(IEntityType entityType)
{
if (entityType.FindAnnotation(SqlServerEntityTypeBuilderExtensions.ANNOTATION_TEMPORAL) != null)
{
var asOfTableExpression = new AsOfTableExpression(
entityType.GetTableName(),
entityType.GetSchema(),
entityType.GetTableName().ToLower().Substring(0, 1));
var selectContructor = typeof(SelectExpression).GetConstructor(BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance, null, new Type[] { typeof(IEntityType), typeof(TableExpressionBase) }, null);
var select = (SelectExpression)selectContructor.Invoke(new object[] { entityType, asOfTableExpression });
var privateInitializer = typeof(SqlExpressionFactory).GetMethod("AddConditions", BindingFlags.NonPublic | BindingFlags.Instance);
privateInitializer.Invoke(this, new object[] { select, entityType, null, null });
return(select);
}
return(base.Select(entityType));
}