/// <summary>
/// This is internal API and is not intended for use by Linq To DB applications.
/// It may change or be removed without further notice.
/// </summary>
public static SqlUpdateClause RequireUpdateClause(this SqlStatement statement)
{
var result = statement.GetUpdateClause();
if (result == null)
{
throw new LinqToDBException($"Update clause not found in {statement.GetType().Name}");
}
return(result);
}
public static Tuple <SqlTableSource, SqlTableSource> MoveJoinsToSubqueries(
this SqlStatement statement,
string firstTableAlias,
string secondTableAlias,
BasicMergeBuilder.QueryElement part)
{
var baseTablesCount = secondTableAlias == null ? 1 : 2;
// collect tables, referenced in FROM clause
var tableSet = new HashSet <SqlTable>();
var tables = new List <SqlTable>();
new QueryVisitor().Visit(statement.SelectQuery.From, e => {
if (e.ElementType == QueryElementType.TableSource)
{
var et = (SqlTableSource)e;
tableSet.Add((SqlTable)et.Source);
tables.Add((SqlTable)et.Source);
}
});
if (tables.Count > baseTablesCount)
{
var firstTable = (SqlTable)statement.SelectQuery.From.Tables[0].Source;
var secondTable = baseTablesCount > 1
? (SqlTable)statement.SelectQuery.From.Tables[0].Joins[0].Table.Source
: null;
ISqlExpressionWalkable queryPart;
switch (part)
{
case BasicMergeBuilder.QueryElement.Where:
queryPart = statement.SelectQuery.Where;
break;
case BasicMergeBuilder.QueryElement.InsertSetter:
queryPart = statement.GetInsertClause();
break;
case BasicMergeBuilder.QueryElement.UpdateSetter:
queryPart = statement.GetUpdateClause();
break;
default:
throw new InvalidOperationException();
}
queryPart.Walk(new WalkOptions(true), element => statement.SelectQuery.ConvertToSubquery(element, tableSet, tables, firstTable, secondTable));
}
var table1 = statement.SelectQuery.From.Tables[0];
table1.Alias = firstTableAlias;
SqlTableSource table2 = null;
if (secondTableAlias != null)
{
if (tables.Count > baseTablesCount)
{
table2 = statement.SelectQuery.From.Tables[0].Joins[0].Table;
}
else
{
table2 = statement.SelectQuery.From.Tables[1];
}
table2.Alias = secondTableAlias;
}
return(Tuple.Create(table1, table2));
}