private static IEnumerable <CosmosElement> ProjectOnGroupings(
IEnumerable <IGrouping <GroupByKey, CosmosElement> > groupings,
SqlSelectClause sqlSelectClause)
{
foreach (IGrouping <GroupByKey, CosmosElement> grouping in groupings)
{
IEnumerable <CosmosElement> dataSource = grouping;
if (AggregateProjectionDector.HasAggregate(sqlSelectClause.SelectSpec))
{
// If there is an aggregate then we need to just project out the one document
// But we need to transform the query to first evaluate the aggregate on all the documents
AggregateProjectionTransformer aggregateProjectionTransformer = new AggregateProjectionTransformer(dataSource);
SqlSelectSpec transformedSpec = aggregateProjectionTransformer
.TransformAggregatesInProjection(sqlSelectClause.SelectSpec);
CosmosElement aggregationResult = transformedSpec.Accept(
Projector.Singleton,
dataSource.FirstOrDefault());
if (aggregationResult != null)
{
dataSource = new CosmosElement[] { aggregationResult };
}
else
{
dataSource = Array.Empty <CosmosElement>();
}
}
else
{
dataSource = dataSource
.Select(element => sqlSelectClause.SelectSpec.Accept(
Projector.Singleton,
element))
.Where(projection => projection != Undefined);
}
if (dataSource.Any())
{
yield return(dataSource.First());
}
}
}
public static IEnumerable <CosmosElement> ExecuteQuery(
IEnumerable <CosmosElement> dataSource,
SqlQuery sqlQuery,
IReadOnlyDictionary <string, PartitionKeyRange> ridToPartitionKeyRange = null)
{
if (dataSource == null)
{
throw new ArgumentNullException($"{nameof(dataSource)} must not be null.");
}
if (sqlQuery == null)
{
throw new ArgumentNullException($"{nameof(sqlQuery)} must not be null.");
}
PerformStaticAnalysis(sqlQuery);
if (ridToPartitionKeyRange == null)
{
ridToPartitionKeyRange = SinglePartitionRidToPartitionKeyRange.Value;
}
// From clause binds the data for the rest of the pipeline
if (sqlQuery.FromClause != null)
{
dataSource = ExecuteFromClause(
dataSource,
sqlQuery.FromClause);
}
else
{
dataSource = NoFromClauseDataSource;
}
// We execute the filter here to reduce the data set as soon as possible.
if (sqlQuery.WhereClause != null)
{
dataSource = ExecuteWhereClause(
dataSource,
sqlQuery.WhereClause);
}
// We sort before the projection,
// since the projection might remove the order by items.
if (sqlQuery.OrderByClause != null)
{
dataSource = ExecuteOrderByClause(
dataSource,
sqlQuery.OrderByClause,
ridToPartitionKeyRange);
}
else
{
// Even for non order by queries we need to order by partition key ranges and document ids
dataSource = ExecuteCrossPartitionOrdering(
dataSource,
ridToPartitionKeyRange);
}
IEnumerable <IGrouping <GroupByKey, CosmosElement> > groupings;
// We need to create the groupings at this point for the rest of the pipeline
if (sqlQuery.GroupByClause != null)
{
groupings = ExecuteGroupByClause(
dataSource,
sqlQuery.GroupByClause);
}
else
{
if (AggregateProjectionDector.HasAggregate(sqlQuery.SelectClause.SelectSpec))
{
groupings = CreateOneGroupingForWholeCollection(dataSource);
}
else
{
groupings = CreateOneGroupingForEachDocument(dataSource);
}
}
// We finally project out the needed columns and remove all binding artifacts
dataSource = ExecuteSelectClause(
groupings,
sqlQuery.SelectClause);
// Offset limit just performs skip take
if (sqlQuery.OffsetLimitClause != null)
{
dataSource = ExecuteOffsetLimitClause(dataSource, sqlQuery.OffsetLimitClause);
}
return(dataSource);
}
