/// <summary>
/// 表达式生成删除语句。
/// </summary>
/// <param name="context">生成上下文。</param>
/// <param name="content">生成表达式。</param>
/// <returns>语句片段。</returns>
protected virtual SqlFragment GenerateForDeleteStatement(GenerateContext context, DbExpression content)
{
var data = (StatementContent)context.Data;
var item = data.ItemEpxression;
var source = CreateSource(context, content) as QueryBaseFragment;
var table = data.Table;
if (table.InheritSets.Length == 0)
{
var target = (TableFragment)GetSource(context, item);
target.Name = context.ConvertName(data.TargetName);
var delete = new DeleteFragment(context, target)
{
Where = source.Where,
Take = source.Take
};
delete.AddSource(source.Sources.Where(a => a != target));
return(delete);
}
else
{
var createtable = new CreateTempTableFragment(context, table.Keys);
var insert = new InsertFragment(context, createtable.Table, source);
insert.Members.AddRange(createtable.Table.Members);
foreach (var key in table.Keys)
{
RetrievalMember(context, source, new DbMemberExpression(key.Member, item), null, false);
}
var block = new BlockFragment(context, createtable, insert);
foreach (var subtable in table.InheritSets.Concat(new TableMetadata[] { table }).Reverse())
{
var current = new TableFragment(context, subtable);
var delete = new DeleteFragment(context, current);
var temptable = new TemporaryTableFragment(context, table.Keys, createtable.Table.Name);
current.Join(temptable, table.Keys);
delete.AddSource(temptable);
block.Add(delete);
}
return(block);
}
}
/// <summary>
/// 使用临时表形式，生成删除多个复合关系的语句，
/// 要求数据库拥有<see cref="EDbCapable.TemporaryTable"/>
/// 和<see cref="EDbCapable.ModifyJoin"/>两个特性。
/// </summary>
/// <param name="context">生成上下文。</param>
/// <returns>语句片段。</returns>
protected virtual SqlFragment GenerateForRelationDeleteTempTable(GenerateContext context)
{
var data = (RelationContent)context.Data;
var composite = (CompositeNavigateMetadata)data.Items.Navigate;
var createtemptable = new CreateTempTableFragment(context,
composite.Pairs.Select(a => a.ForeignKey).Concat(composite.CompositePairs.Select(a => a.ForeignKey)));
var insert = new InsertValueFragment(context, createtemptable.Table, data.CommitObject, data.Items);
composite.Pairs.ForEach(pair => insert.SetValue(pair.ForeignKey, data.CommitObject.GetMember(pair.PrincipalKey)));
composite.CompositePairs.ForEach(pair => insert.SetValue(pair.ForeignKey, data.CommitObject.GetMember(pair.PrincipalKey)));
var temptable = createtemptable.Table;
var target = new TableFragment(context, data.Table);
var delete = new DeleteFragment(context, target);
delete.AddSource(temptable);
target.Join(temptable, composite.Pairs.Select(a => a.ForeignKey).Concat(composite.CompositePairs.Select(a => a.ForeignKey)));
return(new BlockFragment(context, createtemptable, insert, delete));
}
/// <inheritdoc/>
protected override SqlFragment GenerateForRelation(GenerateContext context, DbExpression content)
{
var data = (RelationContent)context.Data;
if (data.Items.Count > 1)
{
var metadata = data.Items.Navigate;
if (data.IsAddRelation && !metadata.IsComposite)
{
var columns = data.Source.Keys.Concat(metadata.Pairs.Select(a => a.ForeignKey));
var values = new ValuesFragment(context, data.CommitObject, data.Items);
data.Source.Keys.ForEach(key => values.SetValue(key));
if (data.IsAddRelation)
{
metadata.Pairs.ForEach(
pair => values.SetValue(pair.ForeignKey, data.CommitObject.GetMember(pair.PrincipalKey)));
}
var update = new UpdateFragment(context, data.Table);
update.AddSource(update.Target, values);
foreach (var pair in metadata.Pairs)
{
update.SetValue(pair.ForeignKey, values.GetMember(pair.ForeignKey));
}
update.Target.Join(values, data.Table.Keys);
return(update);
}
else if (!data.IsAddRelation && metadata.IsComposite)
{
var composite = (CompositeNavigateMetadata)data.Items.Navigate;
var values = new ValuesFragment(context, data.CommitObject, data.Items);
composite.Pairs.ForEach(pair => values.SetValue(pair.ForeignKey, data.CommitObject.GetMember(pair.PrincipalKey)));
composite.CompositePairs.ForEach(pair => values.SetValue(pair.ForeignKey, data.CommitObject.GetMember(pair.PrincipalKey)));
var target = new TableFragment(context, data.Table);
var delete = new DeleteFragment(context, target);
delete.AddSource(values);
target.Join(values, composite.Pairs.Select(a => a.ForeignKey).Concat(composite.CompositePairs.Select(a => a.ForeignKey)));
return(delete);
}
}
return(base.GenerateForRelation(context, content));
}
