private static bool GetNextRelationAndTable(DbRelationCollection allRelations, List<JoinMode> allJoinModes, TableWithJoinMode[] usedTables, out DbRelation nextRelation, out TableWithJoinMode nextTable)
{
nextRelation = null;
nextTable = null;
for (int idxRelation = 0; idxRelation < allRelations.Count; idxRelation++)
{
DbRelation currentRelation = allRelations[idxRelation];
IDbTable newTableCandidate = null;
TableWithJoinMode alreadyUsedTableFromCurrentRelation = null;
bool connectAsOuter = false;
int numOfTablesCurrentRelationConnects = 0;
// Check how many of the used tables current relation connects.
for (int idxTable = 0; idxTable < usedTables.Length; idxTable++)
{
if (usedTables[idxTable] == null)
continue;
if (currentRelation.Parent.HasEqualAliasAndNameAs(usedTables[idxTable].Table))
{
// Parent table is already in the ordered from tables list.
numOfTablesCurrentRelationConnects++;
newTableCandidate = currentRelation.Child;
alreadyUsedTableFromCurrentRelation = usedTables[idxTable];
if (allJoinModes[idxRelation].ChildrenAsOuter == true)
connectAsOuter = true;
}
if (currentRelation.Child.HasEqualAliasAndNameAs(usedTables[idxTable].Table))
{
// Child table is already in the ordered from tables list.
numOfTablesCurrentRelationConnects++;
newTableCandidate = currentRelation.Parent;
alreadyUsedTableFromCurrentRelation = usedTables[idxTable];
if (allJoinModes[idxRelation].ParentAsOuter == true)
connectAsOuter = true;
}
}
// If current relation connects only one used table than the other one is a new table.
// Return the new relation and table.
if (numOfTablesCurrentRelationConnects == 1)
{
// If the already used table is connected as outer then the new one MUST be outer, too.
if (alreadyUsedTableFromCurrentRelation.JoinAsOuter == true)
connectAsOuter = true;
nextRelation = currentRelation;
nextTable = new TableWithJoinMode(newTableCandidate, connectAsOuter);
return true;
}
}
return false;
}
private static void SortRelationsAndJoinModes(DbRelationCollection allRelations, List<JoinMode> allJoinModes, IDbTable firstTable, out DbRelation[] orderedRelations, out TableWithJoinMode[] orderedFromTables)
{
// Sorts relations in a fashion so that only INNER and LEFT OUTER joins are used. RIGHT joins will never be required.
orderedRelations = new DbRelation[allRelations.Count];
int relationIdx = 0;
orderedFromTables = new TableWithJoinMode[allJoinModes.Count + 1];
int fromIdx = 0;
// JoinAsOuter property doesn't doesn't affect 1st table.
orderedFromTables[fromIdx] = new TableWithJoinMode(firstTable, false);
fromIdx++;
DbRelation nextRelation;
TableWithJoinMode nextTable;
while (GetNextRelationAndTable(allRelations, allJoinModes, orderedFromTables, out nextRelation, out nextTable))
{
orderedRelations[relationIdx++] = nextRelation;
orderedFromTables[fromIdx++] = nextTable;
}
}
