public QueryOptimization(Snapshot snapshot, Query query, IEnumerable<BsonDocument> source, Collation collation)
{
if (query.Select == null) throw new ArgumentNullException(nameof(query.Select));
_snapshot = snapshot;
_query = query;
_collation = collation;
_queryPlan = new QueryPlan(snapshot.CollectionName)
{
// define index only if source are external collection
Index = source != null ? new IndexVirtual(source) : null,
Select = new Select(_query.Select, _query.Select.UseSource),
ForUpdate = query.ForUpdate,
Limit = query.Limit,
Offset = query.Offset
};
}
/// <summary> /// Abstract method to be implement according pipe workflow /// </summary> public abstract IAsyncEnumerable <BsonDocument> Pipe(IAsyncEnumerable <IndexNode> nodes, QueryPlan query);
/// <summary>
/// Query Pipe order
/// - LoadDocument
/// - IncludeBefore
/// - Filter
/// - OrderBy
/// - OffSet
/// - Limit
/// - IncludeAfter
/// - Select
/// </summary>
public override IEnumerable <BsonDocument> Pipe(IEnumerable <IndexNode> nodes, QueryPlan query)
{
// starts pipe loading document
var source = this.LoadDocument(nodes);
// do includes in result before filter
foreach (var path in query.IncludeBefore)
{
source = this.Include(source, path);
}
// filter results according expressions
foreach (var expr in query.Filters)
{
source = this.Filter(source, expr);
}
if (query.OrderBy != null)
{
// pipe: orderby with offset+limit
source = this.OrderBy(source, query.OrderBy.Expression, query.OrderBy.Order, query.Offset, query.Limit);
}
else
{
// pipe: apply offset (no orderby)
if (query.Offset > 0)
{
source = source.Skip(query.Offset);
}
// pipe: apply limit (no orderby)
if (query.Limit < int.MaxValue)
{
source = source.Take(query.Limit);
}
}
// do includes in result after filter
foreach (var path in query.IncludeAfter)
{
source = this.Include(source, path);
}
// if is an aggregate query, run select transform over all resultset - will return a single value
if (query.Select.All)
{
return(this.SelectAll(source, query.Select.Expression));
}
// run select transform in each document and return a new document or value
else
{
return(this.Select(source, query.Select.Expression));
}
}
/// <summary>
/// GroupBy Pipe Order
/// - LoadDocument
/// - Filter
/// - OrderBy (to GroupBy)
/// - GroupBy
/// - HavingSelectGroupBy
/// - OffSet
/// - Limit
/// </summary>
public override IEnumerable <BsonDocument> Pipe(IEnumerable <IndexNode> nodes, QueryPlan query)
{
// starts pipe loading document
var source = this.LoadDocument(nodes);
// filter results according filter expressions
foreach (var expr in query.Filters)
{
source = this.Filter(source, expr);
}
// run orderBy used in GroupBy (if not already ordered by index)
if (query.OrderBy != null)
{
source = this.OrderBy(source, query.OrderBy.Expression, query.OrderBy.Order, 0, int.MaxValue);
}
// apply groupby
var groups = this.GroupBy(source, query.GroupBy);
// apply group filter and transform result
var result = this.SelectGroupBy(groups, query.GroupBy);
// apply offset
if (query.Offset > 0)
{
result = result.Skip(query.Offset);
}
// apply limit
if (query.Limit < int.MaxValue)
{
result = result.Take(query.Limit);
}
return(result);
}
/// <summary>
/// Query Pipe order
/// - LoadDocument
/// - IncludeBefore
/// - Filter
/// - OrderBy
/// - OffSet
/// - Limit
/// - IncludeAfter
/// - Select
/// </summary>
public override async IAsyncEnumerable <BsonDocument> Pipe(IAsyncEnumerable <IndexNode> nodes, QueryPlan query)
{
// starts pipe loading document
var source = this.LoadDocument(nodes);
// do includes in result before filter
foreach (var path in query.IncludeBefore)
{
source = this.Include(source, path);
}
// filter results according expressions
foreach (var expr in query.Filters)
{
source = this.Filter(source, expr);
}
if (query.OrderBy != null)
{
// pipe: orderby with offset+limit
source = this.OrderBy(source, query.OrderBy.Expression, query.OrderBy.Order, query.Offset, query.Limit);
}
else
{
// pipe: apply offset (no orderby)
if (query.Offset > 0)
{
source = source.SkipAsync(query.Offset);
}
// pipe: apply limit (no orderby)
if (query.Limit < int.MaxValue)
{
source = source.TakeAsync(query.Limit);
}
}
// do includes in result after filter
foreach (var path in query.IncludeAfter)
{
source = this.Include(source, path);
}
var result = query.Select.All ?
this.SelectAll(source, query.Select.Expression) :
this.Select(source, query.Select.Expression);
await foreach (var doc in result)
{
yield return(doc);
}
}
