/// <summary>
/// Creates a new instance of the <see cref="SearchParamTableExpression"/> class.
/// </summary>
/// <param name="queryGenerator">The search parameter query generator</param>
/// <param name="predicate">The search expression over a columns belonging exclusively to a search parameter table.
/// Applies to the chain target if a chained expression.</param>
/// <param name="kind">The table expression kind.</param>
/// <param name="chainLevel">The nesting chain nesting level of the current expression. 0 if not a chain expression.</param>
public SearchParamTableExpression(
SearchParamTableExpressionQueryGenerator queryGenerator,
Expression predicate,
SearchParamTableExpressionKind kind,
int chainLevel = 0)
{
QueryGenerator = queryGenerator;
Predicate = predicate;
Kind = kind;
ChainLevel = chainLevel;
}
public override Expression VisitSqlRoot(SqlRootExpression expression, SqlSearchOptions context)
{
// If we only need the count, we don't want to execute any sort specific queries.
if (context.CountOnly)
{
return(expression);
}
// Proceed if no sort params were requested.
if (context.Sort.Count == 0)
{
return(expression);
}
// _type and _lastUpdated sort params are handled differently than others, because they can be
// inferred directly from the resource table itself.
if (context.Sort.All(s => s.searchParameterInfo.Name is SearchParameterNames.ResourceType or SearchParameterNames.LastUpdated))
{
return(expression);
}
// Check if the parameter being sorted on is also part of another parameter for the search.
// If the parameter being sorted on is part of a filter then we don't need to run the seperate search for resources that are missing a value for the field being sorted on.
// If the parameter being sorted on is not part of a filter we need to run a seperate search to get resources that don't have a value for the field being sorted on.
bool matchFound = false;
for (int i = 0; i < expression.SearchParamTableExpressions.Count; i++)
{
Expression updatedExpression = expression.SearchParamTableExpressions[i].Predicate.AcceptVisitor(this, context);
if (updatedExpression == null)
{
matchFound = true;
break;
}
}
var newTableExpressions = new List <SearchParamTableExpression>();
newTableExpressions.AddRange(expression.SearchParamTableExpressions);
var continuationToken = ContinuationToken.FromString(context.ContinuationToken);
if (!matchFound)
{
// We are running a sort query where the parameter by which we are sorting
// is not present as part of other search parameters in the query.
// Check whether we have to execute the second phase of the search for a sort query.
// This can occur when SearchService decides to run a second search while processing the current query.
// Or it could be a query from the client with a hardcoded "special" continuation token.
if (context.SortQuerySecondPhase ||
(continuationToken != null &&
continuationToken.ResourceSurrogateId == 0 &&
continuationToken.SortValue == SqlSearchConstants.SortSentinelValueForCt))
{
context.ContinuationToken = null;
if (context.Sort[0].sortOrder == SortOrder.Descending)
{
// For descending order, the second phase of the sort query deals with searching
// for resources that do not have a value for the _sort parameter.
var missingExpression = Expression.MissingSearchParameter(context.Sort[0].searchParameterInfo, isMissing: true);
var queryGenForMissing = _searchParamTableExpressionQueryGeneratorFactory.GetSearchParamTableExpressionQueryGenerator(context.Sort[0].searchParameterInfo);
var notExistsExpression = new SearchParamTableExpression(
queryGenForMissing,
missingExpression,
SearchParamTableExpressionKind.NotExists);
newTableExpressions.Add(notExistsExpression);
return(new SqlRootExpression(newTableExpressions, expression.ResourceTableExpressions));
}
// For ascending, the second phase of the sort query deals with searching
// for resources that have a value for the _sort parameter. So we will generate
// the appropriate Sort expression below.
}
else if (continuationToken != null && continuationToken.SortValue == null)
{
// We have a ct for resourceid but not for the sort value.
// This means we are paging through resources that do not have values for the _sort parameter.
var missingExpression = Expression.MissingSearchParameter(context.Sort[0].searchParameterInfo, isMissing: true);
var queryGenForMissing = _searchParamTableExpressionQueryGeneratorFactory.GetSearchParamTableExpressionQueryGenerator(context.Sort[0].searchParameterInfo);
var notExistsExpression = new SearchParamTableExpression(
queryGenForMissing,
missingExpression,
SearchParamTableExpressionKind.NotExists);
newTableExpressions.Add(notExistsExpression);
return(new SqlRootExpression(newTableExpressions, expression.ResourceTableExpressions));
}
else if (continuationToken == null)
{
// This means we are in the first "phase" of searching for resources for the _sort query.
// For ascending order, we will search for resources that do not have a value for the
// corresponding _sort parameter.
if (context.Sort[0].sortOrder == SortOrder.Ascending)
{
var missingExpression = Expression.MissingSearchParameter(context.Sort[0].searchParameterInfo, isMissing: true);
var queryGenForMissing = _searchParamTableExpressionQueryGeneratorFactory.GetSearchParamTableExpressionQueryGenerator(context.Sort[0].searchParameterInfo);
var notExistsExpression = new SearchParamTableExpression(
queryGenForMissing,
missingExpression,
SearchParamTableExpressionKind.NotExists);
newTableExpressions.Add(notExistsExpression);
return(new SqlRootExpression(newTableExpressions, expression.ResourceTableExpressions));
}
// For descending order, we will search for resources that have a value for the
// corresponding _sort parameter. We will generate the appropriate Sort expression below.
}
}
SearchParamTableExpressionKind sortKind = matchFound ? SearchParamTableExpressionKind.SortWithFilter : SearchParamTableExpressionKind.Sort;
if (sortKind == SearchParamTableExpressionKind.SortWithFilter)
{
context.IsSortWithFilter = true;
}
var queryGenerator = _searchParamTableExpressionQueryGeneratorFactory.GetSearchParamTableExpressionQueryGenerator(context.Sort[0].searchParameterInfo);
newTableExpressions.Add(new SearchParamTableExpression(queryGenerator, new SortExpression(context.Sort[0].searchParameterInfo), sortKind));
return(new SqlRootExpression(newTableExpressions, expression.ResourceTableExpressions));
}