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Make query execution truly asynchronous (#83)

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The two main changes in this pull request:
Launching query execution as an asynchronous task that performs a callback upon completion or failure of a query. (Which also sets us up for callbacks progressive results)
Moving away from using the Result of a query execution to return an error. Instead we'll use an error event to return an error
Additionally, some nice refactoring and cleaning up of the unit tests to take advantage of the cool RequestContext mock tooling by @kevcunnane

* Initial commit of refactor to run execution truely asynchronously

* Moving the storage of the task into Query class

Callbacks for completion of a query and failure of a query are setup as
events in the Query class. This actually sets us up for a very nice
framework for adding batch and resultset completion callbacks.

However, this also exposes a problem with cancelling queries and returning
errors -- we don't properly handle errors during execution of a query
(aside from DB errors).

* Wrapping things up in order to submit for code review

* Adding fixes as per comments
This commit is contained in:
Benjamin Russell
2016-10-11 10:51:52 -07:00
committed by GitHub
parent a2f2dd7b5e
commit 60edcc3057
12 changed files with 272 additions and 282 deletions
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95
src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Query.cs
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@@ -96,6 +96,22 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
#region Properties
/// <summary>
/// Delegate type for callback when a query completes or fails
/// </summary>
/// <param name="q">The query that completed</param>
public delegate Task QueryAsyncEventHandler(Query q);
/// <summary>
/// Callback for when the query has completed successfully
/// </summary>
public event QueryAsyncEventHandler QueryCompleted;
/// <summary>
/// Callback for when the query has failed
/// </summary>
public event QueryAsyncEventHandler QueryFailed;
/// <summary>
/// The batches underneath this query
/// </summary>
@@ -124,6 +140,8 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
}
}
internal Task ExecutionTask { get; private set; }
/// <summary>
/// Whether or not the query has completed executed, regardless of success or failure
/// </summary>
@@ -167,10 +185,44 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
cancellationSource.Cancel();
}
public void Execute()
{
ExecutionTask = Task.Run(ExecuteInternal);
}
/// <summary>
/// Retrieves a subset of the result sets
/// </summary>
/// <param name="batchIndex">The index for selecting the batch item</param>
/// <param name="resultSetIndex">The index for selecting the result set</param>
/// <param name="startRow">The starting row of the results</param>
/// <param name="rowCount">How many rows to retrieve</param>
/// <returns>A subset of results</returns>
public Task<ResultSetSubset> GetSubset(int batchIndex, int resultSetIndex, int startRow, int rowCount)
{
// Sanity check that the results are available
if (!HasExecuted)
{
throw new InvalidOperationException(SR.QueryServiceSubsetNotCompleted);
}
// Sanity check to make sure that the batch is within bounds
if (batchIndex < 0 || batchIndex >= Batches.Length)
{
throw new ArgumentOutOfRangeException(nameof(batchIndex), SR.QueryServiceSubsetBatchOutOfRange);
}
return Batches[batchIndex].GetSubset(resultSetIndex, startRow, rowCount);
}
#endregion
#region Private Helpers
/// <summary>
/// Executes this query asynchronously and collects all result sets
/// </summary>
public async Task Execute()
private async Task ExecuteInternal()
{
// Mark that we've internally executed
hasExecuteBeenCalled = true;
@@ -202,6 +254,20 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
{
await b.Execute(conn, cancellationSource.Token);
}
// Call the query execution callback
if (QueryCompleted != null)
{
await QueryCompleted(this);
}
}
catch (Exception)
{
// Call the query failure callback
if (QueryFailed != null)
{
await QueryFailed(this);
}
}
finally
{
@@ -227,7 +293,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
throw new InvalidOperationException(SR.QueryServiceMessageSenderNotSql);
}
foreach(SqlError error in args.Errors)
foreach (SqlError error in args.Errors)
{
// Did the database context change (error code 5701)?
if (error.Number == DatabaseContextChangeErrorNumber)
@@ -237,31 +303,6 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
}
}
/// <summary>
/// Retrieves a subset of the result sets
/// </summary>
/// <param name="batchIndex">The index for selecting the batch item</param>
/// <param name="resultSetIndex">The index for selecting the result set</param>
/// <param name="startRow">The starting row of the results</param>
/// <param name="rowCount">How many rows to retrieve</param>
/// <returns>A subset of results</returns>
public Task<ResultSetSubset> GetSubset(int batchIndex, int resultSetIndex, int startRow, int rowCount)
{
// Sanity check that the results are available
if (!HasExecuted)
{
throw new InvalidOperationException(SR.QueryServiceSubsetNotCompleted);
}
// Sanity check to make sure that the batch is within bounds
if (batchIndex < 0 || batchIndex >= Batches.Length)
{
throw new ArgumentOutOfRangeException(nameof(batchIndex), SR.QueryServiceSubsetBatchOutOfRange);
}
return Batches[batchIndex].GetSubset(resultSetIndex, startRow, rowCount);
}
#endregion
#region IDisposable Implementation