/// <summary>
/// Provides language specific query translation. Use this to apply language specific rewrites or
/// to make assertions/validations about the query.
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
public virtual Expression Translate(Expression expression)
{
// remove redundant layers again before cross apply rewrite
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
// convert cross-apply and outer-apply joins into inner & left-outer-joins if possible
var rewritten = CrossApplyRewriter.Rewrite(this.language, expression);
// convert cross joins into inner joins
rewritten = CrossJoinRewriter.Rewrite(rewritten);
if (rewritten != expression)
{
expression = rewritten;
// do final reduction
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
}
return(expression);
}
/// <summary>
/// Apply mapping translations to this expression
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
public virtual Expression Translate(Expression expression)
{
// convert references to LINQ operators into query specific nodes
expression = QueryBinder.Bind(this, expression);
// move aggregate computations so they occur in same select as group-by
expression = AggregateRewriter.Rewrite(this.Translator.Linguist.Language, expression);
// do reduction so duplicate association's are likely to be clumped together
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
// convert references to association properties into correlated queries
var bound = RelationshipBinder.Bind(this, expression);
if (bound != expression)
{
expression = bound;
// clean up after ourselves! (multiple references to same association property)
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
}
// rewrite comparision checks between entities and multi-valued constructs
expression = ComparisonRewriter.Rewrite(this.Mapping, expression);
return(expression);
}
/// <summary>
/// Provides policy specific query translations. This is where choices about inclusion of related objects and how
/// heirarchies are materialized affect the definition of the queries.
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
public virtual Expression Translate(Expression expression)
{
// add included relationships to client projection
var rewritten = RelationshipIncluder.Include(this.translator.Mapper, expression);
if (rewritten != expression)
{
expression = rewritten;
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
}
// convert any singleton (1:1 or n:1) projections into server-side joins (cardinality is preserved)
rewritten = SingletonProjectionRewriter.Rewrite(this.translator.Linguist.Language, expression);
if (rewritten != expression)
{
expression = rewritten;
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
}
// convert projections into client-side joins
rewritten = ClientJoinedProjectionRewriter.Rewrite(this.policy, this.translator.Linguist.Language, expression);
if (rewritten != expression)
{
expression = rewritten;
expression = UnusedColumnRemover.Remove(expression);
expression = RedundantColumnRemover.Remove(expression);
expression = RedundantSubqueryRemover.Remove(expression);
expression = RedundantJoinRemover.Remove(expression);
}
return(expression);
}
public static Expression Remove(Expression expression)
{
expression = new RedundantSubqueryRemover().Visit(expression);
expression = SubqueryMerger.Merge(expression);
return(expression);
}