Expression VisitSelectExpression(SelectExpression selectExpression)
{
base.Visit(selectExpression);
if (!RequiresRowNumberPaging(selectExpression))
{
return(selectExpression);
}
var subQuery = selectExpression.PushDownSubquery();
foreach (var projection in subQuery.Projection)
{
selectExpression.AddToProjection(projection.LiftExpressionFromSubquery(subQuery));
}
if (subQuery.OrderBy.Count == 0)
{
subQuery.AddToOrderBy(
new Ordering(new SqlFunctionExpression("@@RowCount", typeof(int)), OrderingDirection.Asc));
}
var innerRowNumberExpression = new AliasExpression(
RowNumberColumnName + (_counter != 0 ? $"{_counter}" : ""),
new RowNumberExpression_SqlServer(subQuery.OrderBy));
_counter++;
subQuery.ClearOrderBy();
subQuery.AddToProjection(innerRowNumberExpression, false);
var rowNumberReferenceExpression = new ColumnReferenceExpression(innerRowNumberExpression, subQuery);
var offset = subQuery.Offset ?? Expression.Constant(0);
if (subQuery.Offset != null)
{
selectExpression.AddToPredicate
(Expression.GreaterThan(rowNumberReferenceExpression, offset));
subQuery.Offset = null;
}
if (subQuery.Limit != null)
{
var constantValue = (subQuery.Limit as ConstantExpression)?.Value;
var offsetValue = (offset as ConstantExpression)?.Value;
var limitExpression
= constantValue != null &&
offsetValue != null
? (Expression)Expression.Constant((int)offsetValue + (int)constantValue)
: Expression.Add(offset, subQuery.Limit);
selectExpression.AddToPredicate(
Expression.LessThanOrEqual(rowNumberReferenceExpression, limitExpression));
subQuery.Limit = null;
}
return(selectExpression);
}
internal static SelectExpression WhereAndSelectDatabaseExpressions(AdventureWorks adventureWorks)
{
QueryCompilationContext compilationContext = adventureWorks.GetService <IQueryCompilationContextFactory>()
.Create(async: false);
SelectExpression databaseExpression = new SelectExpression(
dependencies: new SelectExpressionDependencies(adventureWorks.GetService <IQuerySqlGeneratorFactory>(), adventureWorks.GetService <IRelationalTypeMappingSource>()),
queryCompilationContext: (RelationalQueryCompilationContext)compilationContext);
MainFromClause querySource = new MainFromClause(
itemName: "product",
itemType: typeof(Product),
fromExpression: Expression.Constant(adventureWorks.ProductCategories));
TableExpression tableExpression = new TableExpression(
table: nameof(Product),
schema: AdventureWorks.Production,
alias: querySource.ItemName,
querySource: querySource);
databaseExpression.AddTable(tableExpression);
IEntityType productEntityType = adventureWorks.Model.FindEntityType(typeof(Product));
IProperty nameProperty = productEntityType.FindProperty(nameof(Product.Name));
ColumnExpression nameColumn = new ColumnExpression(
name: nameof(Product.Name), property: nameProperty, tableExpression: tableExpression);
databaseExpression.AddToProjection(nameColumn);
databaseExpression.AddToPredicate(Expression.GreaterThan(
left: new ExplicitCastExpression(
operand: new SqlFunctionExpression(
functionName: "LEN",
returnType: typeof(int),
arguments: new Expression[] { nameColumn }),
type: typeof(int)),
right: Expression.Constant(10)));
return(databaseExpression.WriteLine());
}
Expression VisitSelectExpression(SelectExpression selectExpression)
{
base.Visit(selectExpression);
if (!RequiresRowNumberPaging(selectExpression))
{
return(selectExpression);
}
SelectExpression selectExpression2 = selectExpression.PushDownSubquery();
foreach (Expression item in selectExpression2.Projection)
{
selectExpression.AddToProjection(item.LiftExpressionFromSubquery(selectExpression2), true);
}
AliasExpression aliasExpression = new AliasExpression("row_number" + ((_counter != 0) ? $"{_counter}" : ""), new RowNumberExpression_DB2(selectExpression2.OrderBy));
_counter++;
selectExpression2.ClearOrderBy();
selectExpression2.AddToProjection(aliasExpression, false);
ColumnReferenceExpression left = new ColumnReferenceExpression(aliasExpression, selectExpression2);
Expression expression = selectExpression2.Offset ?? Expression.Constant(0);
if (selectExpression2.Offset != null)
{
selectExpression.AddToPredicate(Expression.GreaterThan(left, expression));
selectExpression2.Offset = null;
}
if (selectExpression2.Limit != null)
{
object obj = (selectExpression2.Limit as ConstantExpression)?.Value;
object obj2 = (expression as ConstantExpression)?.Value;
Expression right = (obj != null && obj2 != null) ? ((Expression)Expression.Constant((int)obj2 + (int)obj)) : ((Expression)Expression.Add(expression, selectExpression2.Limit));
selectExpression.AddToPredicate(Expression.LessThanOrEqual(left, right));
selectExpression2.Limit = null;
}
return(selectExpression);
}
private Expression VisitSelectExpression(SelectExpression selectExpression)
{
base.Visit(selectExpression);
if (!RequiresRowNumberPaging(selectExpression))
{
return(selectExpression);
}
var subQuery = selectExpression.PushDownSubquery();
if (subQuery.Projection.Count > 0)
{
selectExpression.ExplodeStarProjection();
}
if (subQuery.OrderBy.Count == 0)
{
subQuery.AddToOrderBy(
new Ordering(new SqlFunctionExpression("@@RowCount", typeof(int)), OrderingDirection.Asc));
}
var innerRowNumberExpression = new AliasExpression(
RowNumberColumnName + (_counter != 0 ? $"{_counter}" : ""),
new RowNumberExpression(
subQuery.OrderBy
.Select(
o => new Ordering(
o.Expression is AliasExpression ae ? ae.Expression : o.Expression,
o.OrderingDirection))
.ToList()));
_counter++;
subQuery.ClearOrderBy();
subQuery.AddToProjection(innerRowNumberExpression, resetProjectStar: false);
var rowNumberReferenceExpression = new ColumnReferenceExpression(innerRowNumberExpression, subQuery);
var offset = subQuery.Offset ?? Expression.Constant(0);
if (subQuery.Offset != null)
{
selectExpression.AddToPredicate(
Expression.GreaterThan(
rowNumberReferenceExpression,
ApplyConversion(offset, rowNumberReferenceExpression.Type)));
subQuery.Offset = null;
}
if (subQuery.Limit != null)
{
var constantValue = (subQuery.Limit as ConstantExpression)?.Value;
var offsetValue = (offset as ConstantExpression)?.Value;
var limitExpression
= constantValue != null &&
offsetValue != null
? (Expression)Expression.Constant((int)offsetValue + (int)constantValue)
: Expression.Add(offset, subQuery.Limit);
selectExpression.AddToPredicate(
Expression.LessThanOrEqual(
rowNumberReferenceExpression,
ApplyConversion(limitExpression, rowNumberReferenceExpression.Type)));
subQuery.Limit = null;
}
return(selectExpression);
}
public Expression CreateQueryExpression(Type elementType, DbContext context)
{
var targetType = context.Model.GetEntityTypes().SingleOrDefault(t => t.ClrType == elementType);
Expression queryExpression;
if (targetType.DefiningQuery != null)
{
queryExpression = targetType.DefiningQuery.Body;
goto ApplyQueryFilters;
}
var rootType = targetType.RootType();
var schemaName = rootType.Relational().Schema ?? context.Model.Relational().DefaultSchema;
var tableName = rootType.Relational().TableName;
var table
= new BaseTableExpression(
schemaName,
tableName,
tableName.Substring(0, 1).ToLower(),
rootType.ClrType);
var materializer = CreateMaterializer(targetType, table);
var projection = new ServerProjectionExpression(materializer);
var selectExpression = new SelectExpression(projection, table);
var discriminatingType = targetType;
while (discriminatingType != null)
{
var discriminatorProperty = discriminatingType.Relational().DiscriminatorProperty;
if (discriminatorProperty != null)
{
selectExpression
= selectExpression.AddToPredicate(
new SqlInExpression(
MakeColumnExpression(
table,
discriminatorProperty),
Expression.NewArrayInit(
discriminatorProperty.ClrType,
from t in discriminatingType.GetDerivedTypesInclusive()
where !t.IsAbstract()
select Expression.Constant(
t.Relational().DiscriminatorValue,
discriminatorProperty.ClrType))));
}
discriminatingType = FindSameTabledPrincipalType(discriminatingType);
}
queryExpression = new EnumerableRelationalQueryExpression(selectExpression);
ApplyQueryFilters:
var currentType = targetType;
var recast = false;
while (currentType != null)
{
if (currentType.QueryFilter != null)
{
var filterBody = currentType.QueryFilter.Body;
var repointer
= new QueryFilterRepointingExpressionVisitor(
DbContextParameter.GetInstance(context.GetType()));
filterBody = repointer.Visit(filterBody);
// Use a method call instead of adding to the SelectExpression
// so the rewriting visitors are guaranteed to get their hands on the
// filter.
queryExpression
= Expression.Call(
queryableWhereMethodInfo.MakeGenericMethod(currentType.ClrType),
queryExpression,
Expression.Quote(
Expression.Lambda(
new QueryFilterExpression(filterBody),
currentType.QueryFilter.Parameters)));
recast |= currentType != targetType;
}
currentType = currentType.BaseType;
}
if (recast)
{
queryExpression
= Expression.Call(
queryableCastMethodInfo.MakeGenericMethod(targetType.ClrType),
queryExpression);
}
return(queryExpression);
}