/// <summary>
/// Builds a graph of outer joins given the outer join information from the statement.
/// Eliminates right and left joins and full joins by placing the information in a graph object.
/// </summary>
/// <param name="numStreams">is the number of streams</param>
/// <param name="outerJoinDescList">list of outer join stream numbers and property names</param>
/// <returns>graph object</returns>
public static OuterInnerDirectionalGraph GraphOuterJoins(
int numStreams,
OuterJoinDesc[] outerJoinDescList)
{
if (outerJoinDescList.Length + 1 != numStreams) {
throw new ArgumentException("Number of outer join descriptors and number of streams not matching up");
}
var graph = new OuterInnerDirectionalGraph(numStreams);
for (var i = 0; i < outerJoinDescList.Length; i++) {
var desc = outerJoinDescList[i];
var streamMax = i + 1; // the outer join must references streams less then streamMax
// Check outer join on-expression, if provided
int streamOne;
int streamTwo;
int lowerStream;
int higherStream;
if (desc.OptLeftNode != null) {
streamOne = desc.OptLeftNode.StreamId;
streamTwo = desc.OptRightNode.StreamId;
if (streamOne > streamMax ||
streamTwo > streamMax ||
streamOne == streamTwo) {
throw new ArgumentException("Outer join descriptors reference future streams, or same streams");
}
// Determine who is the first stream in the streams listed
lowerStream = streamOne;
higherStream = streamTwo;
if (streamOne > streamTwo) {
lowerStream = streamTwo;
higherStream = streamOne;
}
}
else {
streamOne = i;
streamTwo = i + 1;
lowerStream = i;
higherStream = i + 1;
graph.AddUnqualifiedNavigable(streamOne, streamTwo);
}
// Add to graph
if (desc.OuterJoinType == OuterJoinType.FULL) {
graph.Add(streamOne, streamTwo);
graph.Add(streamTwo, streamOne);
}
else if (desc.OuterJoinType == OuterJoinType.LEFT) {
graph.Add(lowerStream, higherStream);
}
else if (desc.OuterJoinType == OuterJoinType.RIGHT) {
graph.Add(higherStream, lowerStream);
}
else if (desc.OuterJoinType == OuterJoinType.INNER) {
// no navigability for inner joins
}
else {
throw new ArgumentException(
"Outer join descriptors join type not handled, type=" + desc.OuterJoinType);
}
}
return graph;
}
