public override void Translate(
MethodCallExpression m, TranslationState state, UniqueNameGenerator nameGenerator)
{
// there may not be a preidcate in any method call
IDbObject condition = null;
if (m.GetArguments().Any())
{
condition = state.ResultStack.Pop();
}
var childSelect = (IDbSelect)state.ResultStack.Pop();
var dbSelect = (IDbSelect)state.ResultStack.Peek();
childSelect.Where = condition.ToBinary(_dbFactory);
var dbJoin = dbSelect.Joins.Single(j => ReferenceEquals(j.To.Referee, childSelect));
IDbBinary whereClause = null;
// ReSharper disable once LoopCanBeConvertedToQuery
foreach (var joinKey in dbJoin.Condition.GetOperands().OfType <IDbColumn>().Where(c => ReferenceEquals(c.Ref, dbJoin.To)))
{
var pkColumn = _dbFactory.BuildColumn(dbJoin.To, joinKey.Name, joinKey.ValType.DotNetType, joinKey.Alias);
var binary = _dbFactory.BuildBinary(pkColumn, DbOperator.IsNot, _dbFactory.BuildConstant(null));
whereClause = whereClause.UpdateBinary(binary, _dbFactory);
}
state.ResultStack.Push(whereClause);
}
public static void UpdateWhereClause(this IDbSelect dbSelect, IDbBinary whereClause, IDbObjectFactory dbFactory)
{
if (whereClause == null)
{
return;
}
dbSelect.Where = dbSelect.Where.UpdateBinary(whereClause, dbFactory);
}
public static IDbBinary UpdateBinary(this IDbBinary whereClause, IDbBinary predicate, IDbObjectFactory dbFactory)
{
if (predicate == null)
{
return(whereClause);
}
return(whereClause != null
? dbFactory.BuildBinary(whereClause, DbOperator.And, predicate)
: predicate);
}
public IDbJoin BuildJoin(
DbReference joinTo, IDbSelect dbSelect, IDbBinary condition = null,
DbJoinType dbJoinType = DbJoinType.Inner)
{
var dbJoin = new SqlJoin
{
To = joinTo,
Condition = condition,
Type = dbJoinType
};
joinTo.OwnerSelect = dbSelect;
joinTo.OwnerJoin = dbJoin;
return(dbJoin);
}
/// Create a join for the relation
/// For parent relation, we create a join that joins to the parent table
/// For child relation, we will create a sub select that returns the child table,
/// and then joins to the sub select.
/// The reason for joining to sub select for child relation, is that we want to be
/// able to group on the join key, so that we will not repeat the parent row.
private IDbJoin GetOrCreateJoin(EntityRelation relation, DbReference fromRef, IDbRefColumn refCol)
{
var dbSelect = fromRef.OwnerSelect;
var tupleKey = Tuple.Create(dbSelect, relation);
if (!relation.IsChildRelation && _state.CreatedJoins.ContainsKey(tupleKey))
{
return(_state.CreatedJoins[tupleKey]);
}
var toEntity = relation.ToEntity;
var dbTable = _dbFactory.BuildTable(toEntity);
DbReference joinTo;
DbReference childRef = null;
IDbSelect childSelect = null;
// Create the join. For parent join, we just need to join to a Ref to the table
// For child relation, we will firstly create a sub select that return the child table
// and then join to then sub select
if (!relation.IsChildRelation)
{
var tableAlias = _nameGenerator.GenerateAlias(dbSelect, dbTable.TableName);
joinTo = _dbFactory.BuildRef(dbTable, tableAlias);
}
else
{
childRef = _dbFactory.BuildRef(dbTable);
childSelect = _dbFactory.BuildSelect(childRef);
childRef.Alias = _nameGenerator.GenerateAlias(childSelect, dbTable.TableName);
var tableAlias = _nameGenerator.GenerateAlias(dbSelect, TranslationConstants.SubSelectPrefix, true);
joinTo = _dbFactory.BuildRef(childSelect, tableAlias);
}
var dbJoin = _dbFactory.BuildJoin(joinTo, dbSelect);
dbSelect.Joins.Add(dbJoin);
// build join condition
IDbBinary condition = null;
for (var i = 0; i < relation.FromKeys.Count; i++)
{
var fromKey = relation.FromKeys[i];
var toKey = relation.ToKeys[i];
var fromColumn = _dbFactory.BuildColumn(fromRef, fromKey.DbName, fromKey.ValType);
var toColumn = _dbFactory.BuildColumn(joinTo, toKey.DbName, toKey.ValType);
// If we have created a sub for child relation, we need to the columns
// that are used in join condition selected from the sub select.
if (childRef != null && childSelect != null)
{
var alias = _nameGenerator.GenerateAlias(childSelect, toKey.DbName + TranslationConstants.JoinKeySuffix, true);
var childColumn = _dbFactory.BuildColumn(childRef, toKey.DbName, toKey.ValType, alias, true);
/**
* We need to also put the join key in the group of the sub select.
* This is to make sure the sub select is grouped by the key so that
* the parent (outer select) will not be repeated
* This operation needs to happen here not in the aggregation method call.
* The reason is that in aggregtion method calls we do not know which column
* from the entity is used in relation, so they will not be able to create
* the correct column
*/
childSelect.Selection.Add(_dbFactory.BuildRefColumn(childRef));
childSelect.Selection.Add(childColumn);
childSelect.GroupBys.Add(childColumn);
toColumn.Name = alias;
toColumn.Alias = string.Empty;
}
// if the relation is found on a fromRef which is referring a sub-select,
// it means the from key of the join is not on a table but a derived select.
// In this case, we need to add the from key into the derived select, as we will
// be using it in the join
if (fromRef.Referee is IDbSelect)
{
var alias = _nameGenerator.GenerateAlias(dbSelect, toKey.DbName + TranslationConstants.JoinKeySuffix, true);
fromColumn.Name = alias;
fromColumn.Alias = string.Empty;
// try to recursively add the join key to all connected sub select.
refCol.RefTo?.AddToReferedSelect(_dbFactory, fromKey.DbName, fromKey.ValType, alias);
}
var binary = _dbFactory.BuildBinary(fromColumn, DbOperator.Equal, toColumn);
condition = condition.UpdateBinary(binary, _dbFactory);
}
dbJoin.Condition = condition;
// all relations need to follow the join type
if (fromRef.OwnerJoin != null)
{
dbJoin.Type = fromRef.OwnerJoin.Type;
}
if (relation.IsChildRelation)
{
dbJoin.Type = DbJoinType.LeftOuter;
}
return(_state.CreatedJoins[tupleKey] = dbJoin);
}
