private DataPage <TResource> ExecuteAdjustedQuery <TResource>(string query, Pagination pagination, SortingInstructions sorting, AttributesToFetch attributes = null) where TResource : RmResource
{
attributes = attributes ?? AttributesToFetch.All;
Initialize();
var ctx = LogContext.WithConfigFormat();
_log.Debug(ctx.Format("Executing query {0} with paging: {1}, sorting {2} and attributes {3}"), query, pagination.ToJSON(), sorting.ToJSON(), attributes.GetNames().ToJSON());
// first request - only to get enumeration context and total rows count
var enumerationRequest = new EnumerationRequest(query);
// do not fetch any items - total count only; however this cannot be set to 0 because then total count is not returned (is always set to 0)
enumerationRequest.MaxElements = 1;
// get only ObjectID attribute to minimize overhead caused by this operation which returns elements not used for further processing
enumerationRequest.Selection = new List <string>
{
RmResource.AttributeNames.ObjectID.Name
};
var enumerateResponse = _pagedQueriesClient.Enumerate(enumerationRequest);
long totalCount = enumerateResponse.Count ?? 0;
// second request - to actually get desired data
var pullRequest = new PullRequest();
// set enumeration context from previous query
pullRequest.EnumerationContext = enumerateResponse.EnumerationContext;
// if attributes names to fetch defined...
var attributeNames = attributes.GetNames();
if (attributeNames != null)
{
// ... set them to context
pullRequest.EnumerationContext.Selection = new Selection();
pullRequest.EnumerationContext.Selection.@string = attributeNames.ToList();
}
else
{
pullRequest.EnumerationContext.Selection = null;
}
// if paging defined...
if (pagination.PageSize != Pagination.AllPagesSize)
{
// set current page's first row index...
pullRequest.EnumerationContext.CurrentIndex = pagination.GetFirstRowIndex();
// ...and page size
pullRequest.MaxElements = pagination.PageSize;
}
// ... if not - get all elements
else
{
// reset current row index...
pullRequest.EnumerationContext.CurrentIndex = 0;
// ... page size to max (this may throw if message size exceeds configured maximum, but this situation - getting all items using this method - is not likely to happen)
pullRequest.MaxElements = int.MaxValue;
}
// if sorting defined...
if (sorting != SortingInstructions.None)
{
var sortingAttribute = new SortingAttribute()
{
Ascending = sorting.Order == SortOrder.Ascending,
Value = sorting.AttributeName
};
// due to implementation details of these classes, new instances of each of them needs to be created
pullRequest.EnumerationContext.Sorting = new Sorting
{
SortingAttribute = new List <SortingAttribute>
{
sortingAttribute
}
};
}
var pullResponse = _pagedQueriesClient.Pull(pullRequest);
var results = _defaultClient.ResourceFactory.CreateResource(pullResponse)
.Cast <TResource>()
.ToList();
log_query_executed(ctx, "Paged query {0} returned {1} results and {2} total count", query, results.Count, totalCount);
return(new DataPage <TResource>(results, totalCount));
}
public bool MoveNext()
{
lock (this.client) {
if (resultIndex < results.Count)
{
this.current = results[resultIndex++];
return(true);
}
else
{
PullResponse response;
if (this.context == null)
{
if (resultIndex > 0)
{
// case: previous pull returned an invalid context
return(false);
}
EnumerationRequest request = new EnumerationRequest(filter);
if (attributes != null)
{
request.Selection = new List <string>();
request.Selection.AddRange(this.attributes);
}
response = client.Enumerate(request);
this.endOfSequence = response.EndOfSequence != null;
}
else
{
if (this.endOfSequence == true)
{
// case: previous pull returned an end of sequence flag
this.current = null;
return(false);
}
PullRequest request = new PullRequest();
request.EnumerationContext = this.context;
response = client.Pull(request);
}
if (response == null)
{
return(false);
}
resultIndex = 0;
this.results = resourceFactory.CreateResource(response);
this.context = response.EnumerationContext;
this.endOfSequence = response.IsEndOfSequence;
if (this.results.Count > 0)
{
this.current = results[resultIndex++];
return(true);
}
else
{
this.current = null;
return(false);
}
}
}
}
