private static FilterExpression PrepareJoins(QueryTableSetPlanner tablePlanner, TableSelectExpression expression, TableExpressionFromSet fromSet, FilterExpression whereClause)
{
// Look at the join set and resolve the ON Expression to this statement
JoiningSet joinSet = expression.From.JoinSet;
var result = whereClause;
// Perform a quick scan and see if there are any outer joins in the
// expression.
bool allInnerJoins = true;
for (int i = 0; i < joinSet.TableCount - 1; ++i)
{
JoinType type = joinSet.GetJoinType(i);
if (type != JoinType.Inner)
{
allInnerJoins = false;
}
}
// Prepare the joins
for (int i = 0; i < joinSet.TableCount - 1; ++i)
{
JoinType type = joinSet.GetJoinType(i);
Expression onExpression = joinSet.GetOnExpression(i);
if (allInnerJoins)
{
// If the whole join set is inner joins then simply move the on
// expression (if there is one) to the WHERE clause.
if (onExpression != null)
{
result = result.Append(onExpression);
}
}
else
{
// Not all inner joins,
if (type == JoinType.Inner && onExpression == null)
{
// Regular join with no ON expression, so no preparation necessary
}
else
{
// Either an inner join with an ON expression, or an outer join with
// ON expression
if (onExpression == null)
{
throw new Exception("No ON expression in join.");
}
// Resolve the on_expression
onExpression = onExpression.Prepare(fromSet.ExpressionQualifier);
// And set it in the planner
tablePlanner.SetJoinInfoBetweenSources(i, type, onExpression);
}
}
}
return(result);
}
private static QueryTableSetPlanner SetupPlanners(IDatabaseConnection db, TableExpressionFromSet fromSet)
{
// Set up plans for each table in the from clause of the command. For
// sub-queries, we recurse.
var tablePlanner = new QueryTableSetPlanner();
for (int i = 0; i < fromSet.SetCount; ++i)
{
IFromTableSource table = fromSet.GetTable(i);
if (table is FromTableSubQuerySource)
{
// This represents a sub-command in the FROM clause
var sqlTable = (FromTableSubQuerySource)table;
TableSelectExpression sqlExpr = sqlTable.TableExpression;
TableExpressionFromSet sqlFromSet = sqlTable.FromSet;
// Form a plan for evaluating the sub-command FROM
IQueryPlanNode sqlPlan = FormQueryPlan(db, sqlExpr, sqlFromSet, null);
// The top should always be a SubsetNode,
if (sqlPlan is SubsetNode)
{
var subsetNode = (SubsetNode)sqlPlan;
subsetNode.SetGivenName(sqlTable.AliasedName);
}
else
{
throw new Exception("Top plan is not a SubsetNode!");
}
tablePlanner.AddTableSource(sqlPlan, sqlTable);
}
else if (table is FromTableDirectSource)
{
// This represents a direct referencable table in the FROM clause
var dsTable = (FromTableDirectSource)table;
IQueryPlanNode dsPlan = dsTable.CreateFetchQueryPlanNode();
tablePlanner.AddTableSource(dsPlan, dsTable);
}
else
{
throw new Exception("Unknown table source instance: " + table.GetType());
}
}
return(tablePlanner);
}
