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Refactoring query executor to ensure that transaction is released #2024

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Refactoring query executor to ensure that transaction is released #2024

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86 changes: 38 additions & 48 deletions LiteDB/Engine/Query/QueryExecutor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,75 +63,65 @@ internal BsonDataReader ExecuteQuery(bool executionPlan)

IEnumerable<BsonDocument> RunQuery()
{
var snapshot = transaction.CreateSnapshot(_query.ForUpdate ? LockMode.Write : LockMode.Read, _collection, false);

// no collection, no documents
if (snapshot.CollectionPage == null && _source == null)
try
{
// if query use Source (*) need runs with empty data source
if (_query.Select.UseSource)
{
yield return _query.Select.ExecuteScalar(_pragmas.Collation).AsDocument;
}
var snapshot = transaction.CreateSnapshot(_query.ForUpdate ? LockMode.Write : LockMode.Read, _collection, false);

transaction.OpenCursors.Remove(_cursor);

if (isNew)
// no collection, no documents
if (snapshot.CollectionPage == null && _source == null)
{
_monitor.ReleaseTransaction(transaction);
// if query use Source (*) need runs with empty data source
if (_query.Select.UseSource)
{
yield return _query.Select.ExecuteScalar(_pragmas.Collation).AsDocument;
}
yield break;
}

yield break;
}
// execute optimization before run query (will fill missing _query properties instance)
var optimizer = new QueryOptimization(snapshot, _query, _source, _pragmas.Collation);

// execute optimization before run query (will fill missing _query properties instance)
var optimizer = new QueryOptimization(snapshot, _query, _source, _pragmas.Collation);
var queryPlan = optimizer.ProcessQuery();

var queryPlan = optimizer.ProcessQuery();
// if execution is just to get explan plan, return as single document result
if (executionPlan)
{
yield return queryPlan.GetExecutionPlan();
yield break;
}

// if execution is just to get explan plan, return as single document result
if (executionPlan)
{
yield return queryPlan.GetExecutionPlan();
// get node list from query - distinct by dataBlock (avoid duplicate)
var nodes = queryPlan.Index.Run(snapshot.CollectionPage, new IndexService(snapshot, _pragmas.Collation));

transaction.OpenCursors.Remove(_cursor);
// get current query pipe: normal or groupby pipe
var pipe = queryPlan.GetPipe(transaction, snapshot, _sortDisk, _pragmas);

if (isNew)
try
{
_monitor.ReleaseTransaction(transaction);
}
// start cursor elapsed timer
_cursor.Elapsed.Start();

yield break;
}
// call safepoint just before return each document
foreach (var doc in pipe.Pipe(nodes, queryPlan))
{
_cursor.Fetched++;
_cursor.Elapsed.Stop();

// get node list from query - distinct by dataBlock (avoid duplicate)
var nodes = queryPlan.Index.Run(snapshot.CollectionPage, new IndexService(snapshot, _pragmas.Collation));
yield return doc;

// get current query pipe: normal or groupby pipe
var pipe = queryPlan.GetPipe(transaction, snapshot, _sortDisk, _pragmas);
if (transaction.State != TransactionState.Active) throw new LiteException(0, $"There is no more active transaction for this cursor: {_cursor.Query.ToSQL(_cursor.Collection)}");

try
{
// start cursor elapsed timer
_cursor.Elapsed.Start();

// call safepoint just before return each document
foreach (var doc in pipe.Pipe(nodes, queryPlan))
_cursor.Elapsed.Start();
}
}
finally
{
_cursor.Fetched++;
// stop cursor elapsed
_cursor.Elapsed.Stop();

yield return doc;

if (transaction.State != TransactionState.Active) throw new LiteException(0, $"There is no more active transaction for this cursor: {_cursor.Query.ToSQL(_cursor.Collection)}");

_cursor.Elapsed.Start();
}
}
finally
{
// stop cursor elapsed
_cursor.Elapsed.Stop();

transaction.OpenCursors.Remove(_cursor);

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