// <summary>
// Propagate changes from C-Space (contained in <paramref name="parent" /> to the S-Space.
// </summary>
// <remarks>
// See Walker class for an explanation of this coding pattern.
// </remarks>
// <param name="parent"> Grouper supporting retrieval of changes for C-Space extents referenced in the update mapping view. </param>
// <param name="table"> Table for which updates are being produced. </param>
// <param name="umView"> Update mapping view to propagate. </param>
// <returns> Changes in S-Space. </returns>
internal static ChangeNode Propagate(UpdateTranslator parent, EntitySet table, DbQueryCommandTree umView)
{
// Construct a new instance of a propagator, which implements a visitor interface
// for expression nodes (nodes in the update mapping view) and returns changes nodes
// (seeded by C-Space extent changes returned by the grouper).
DbExpressionVisitor <ChangeNode> propagator = new Propagator(parent, table);
// Walk the update mapping view using the visitor pattern implemented in this class.
// The update mapping view describes the S-Space table we're targeting, so the result
// returned for the root of view corresponds to changes propagated to the S-Space.
return(umView.Query.Accept(propagator));
}
// <summary>
// Constructs a join propagator.
// </summary>
// <param name="left"> Result of propagating changes in the left input to the join </param>
// <param name="right"> Result of propagating changes in the right input to the join </param>
// <param name="node"> Join operator in update mapping view over which to propagate changes </param>
// <param name="parent"> Handler of propagation for the entire update mapping view </param>
internal JoinPropagator(ChangeNode left, ChangeNode right, DbJoinExpression node, Propagator parent)
{
DebugCheck.NotNull(left);
DebugCheck.NotNull(right);
DebugCheck.NotNull(node);
DebugCheck.NotNull(parent);
m_left = left;
m_right = right;
m_joinExpression = node;
m_parent = parent;
Debug.Assert(
DbExpressionKind.LeftOuterJoin == node.ExpressionKind || DbExpressionKind.InnerJoin == node.ExpressionKind,
"(Update/JoinPropagagtor/JoinEvaluator) " +
"caller must ensure only left outer and inner joins are requested");
// Retrieve propagation rules for the join type of the expression.
if (DbExpressionKind.InnerJoin
== m_joinExpression.ExpressionKind)
{
m_insertRules = _innerJoinInsertRules;
m_deleteRules = _innerJoinDeleteRules;
}
else
{
m_insertRules = _leftOuterJoinInsertRules;
m_deleteRules = _leftOuterJoinDeleteRules;
}
// Figure out key selectors involved in the equi-join (if it isn't an equi-join, we don't support it)
JoinConditionVisitor.GetKeySelectors(node.JoinCondition, out m_leftKeySelectors, out m_rightKeySelectors);
// Find the key selector expressions in the left and right placeholders
m_leftPlaceholderKey = ExtractKey(m_left.Placeholder, m_leftKeySelectors);
m_rightPlaceholderKey = ExtractKey(m_right.Placeholder, m_rightKeySelectors);
}
