/// <summary>
/// Returns a list of conditon groups and an associated list of supporting indexes to satisify each group (nested conditions).
/// </summary>
/// <param name="transaction"></param>
/// <param name="schemaMeta"></param>
/// <param name="conditions"></param>
/// <returns></returns>
public List <IndexSelections> SelectIndexes(Transaction transaction, PersistSchema schemaMeta, Conditions conditions)
{
List <IndexSelections> indexSelections = new List <IndexSelections>();
IndexSelections indexSelection = new IndexSelections(conditions);
SelectIndexes(transaction, schemaMeta, conditions.Root, ref indexSelection);
indexSelections.Add(indexSelection);
if (conditions.Children != null && conditions.Children.Count > 0)
{
foreach (var childConditions in conditions.Children)
{
var childIndexSelections = SelectIndexes(transaction, schemaMeta, childConditions);
if (childIndexSelections != null && childIndexSelections.Count > 0)
{
indexSelections.AddRange(childIndexSelections);
}
}
}
return(indexSelections);
}
private void SelectIndexes(Transaction transaction, PersistSchema schemaMeta, List <Condition> conditions, ref IndexSelections indexSelection)
{
try
{
var indexCatalog = GetIndexCatalog(transaction, schemaMeta, LockOperation.Read);
List <PotentialIndex> potentialIndexs = new List <PotentialIndex>();
var indexConditions = new IndexConditions(conditions);
//Loop though each index in the schema and create a list of all indexes which could potentially be used to match the conditions.
foreach (var indexMeta in indexCatalog.Collection)
{
var indexHandledCondition = new List <IndexHandledCondition>();
for (int i = 0; i < indexMeta.Attributes.Count; i++)
{
var indexConditonMatches = indexConditions.FindAll(o => o.Key == indexMeta.Attributes[i].Name.ToLower() && o.Handled == false);
if (indexConditonMatches.Count > 0)
{
foreach (var indexConditonMatche in indexConditonMatches)
{
indexHandledCondition.Add(new IndexHandledCondition(indexConditonMatche, i));
}
}
else
{
break;
}
}
if (indexHandledCondition.Count > 0)
{
potentialIndexs.Add(new PotentialIndex(indexMeta, indexHandledCondition));
}
}
//Group the indexes by their first attribute.
var distinctFirstAttributes = potentialIndexs.Select(o => o.Index.Attributes[0].Name).Distinct();
foreach (var distinctFirstAttribute in distinctFirstAttributes)
{
//Find all idexes with the same first attribute:
var indexGroup = potentialIndexs.Where(o => o.FirstAttributeName == distinctFirstAttribute);
//For the group of indexes, find the one index that handles the most keys but also has the fewest atributes.
var firstIndexInGroup = (from o in indexGroup select o)
.OrderByDescending(s => s.IndexHandledConditions.Count)
.ThenBy(t => t.Index.Attributes.Count).FirstOrDefault();
foreach (var indexHandledCondition in firstIndexInGroup.IndexHandledConditions)
{
//Mark the keys which are handled by this index as "handled".
var handledKeys = (from o in indexConditions where o.Id == indexHandledCondition.Id select o).ToList();
foreach (var handledKey in handledKeys)
{
handledKey.Handled = true;
}
}
indexSelection.Add(new IndexSelection(firstIndexInGroup.Index, firstIndexInGroup.IndexHandledConditions));
}
indexSelection.UnhandledKeys.AddRange((from o in indexConditions where o.Handled == false select o.Key).ToList());
}
catch (Exception ex)
{
core.Log.Write(String.Format("Failed to select indexes for process {0}.", transaction.ProcessId), ex);
throw;
}
}
