Progressive Results Part 1: Batch Completion Notification (#95)

The main feature of this pull request is a new callback that's added to the query class that is called when a batch has completed execution and retrieval of results. This callback will send an event to the extension with the batch summary information. After that, the extension can submit subset requests for the resultsets of the batch.
Other smaller changes in this pull request:
Refactor to assign a batch a id when its created instead of when returning the list of batch summaries
Passing the SelectionData around instead of extracting the values for it
Moving creation of BatchSummary into the Batch class
Retrieval of results is now permitted even if the entire query has not completed, as long as the batch requested has completed.
Also note, this does not break the protocol. It adds a new event that a queryRunner can listen to, but it doesn't require it to be listened to.

* Refactor to remove SectionData class in favor of BufferRange

* Adding callback for batch completion that will let the extension know that a batch has completed execution

* Refactoring to make progressive results work as per async query execution

* Allowing retrieval of batch results while query is in progress

* reverting global.json, whoops

* Adding a few missing comments, and fixing a couple code style bugs

* Using SelectionData everywhere again

* One more missing comment

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Batch.cs

@@ -57,16 +57,19 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
 
         #endregion
 
-        internal Batch(string batchText, int startLine, int startColumn, int endLine, int endColumn, IFileStreamFactory outputFileFactory)
+        internal Batch(string batchText, SelectionData selection, int ordinalId, IFileStreamFactory outputFileFactory)
         {
             // Sanity check for input
             Validate.IsNotNullOrEmptyString(nameof(batchText), batchText);
             Validate.IsNotNull(nameof(outputFileFactory), outputFileFactory);
+            Validate.IsGreaterThan(nameof(ordinalId), ordinalId, 0);
 
             // Initialize the internal state
             BatchText = batchText;
-            Selection = new SelectionData(startLine, startColumn, endLine, endColumn);
+            Selection = selection;
+            executionStartTime = DateTime.Now;
             HasExecuted = false;
+            Id = ordinalId;
             resultSets = new List<ResultSet>();
             resultMessages = new List<ResultMessage>();
             this.outputFileFactory = outputFileFactory;
@@ -74,6 +77,17 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
 
         #region Properties
 
+        /// <summary>
+        /// Asynchronous handler for when batches are completed
+        /// </summary>
+        /// <param name="batch">The batch that completed</param>
+        public delegate Task BatchAsyncEventHandler(Batch batch);
+
+        /// <summary>
+        /// Event that will be called when the batch has completed execution
+        /// </summary>
+        public event BatchAsyncEventHandler BatchCompletion;
+
         /// <summary>
         /// The text of batch that will be executed
         /// </summary>
@@ -113,6 +127,11 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// </summary>
         public bool HasExecuted { get; set; }
 
+        /// <summary>
+        /// Ordinal of the batch in the query
+        /// </summary>
+        public int Id { get; private set; }
+
         /// <summary>
         /// Messages that have come back from the server
         /// </summary>
@@ -145,6 +164,27 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             }
         }
 
+        /// <summary>
+        /// Creates a <see cref="BatchSummary"/> based on the batch instance
+        /// </summary>
+        public BatchSummary Summary
+        {
+            get
+            {
+                return new BatchSummary
+                {
+                    HasError = HasError,
+                    Id = Id,
+                    ResultSetSummaries = ResultSummaries,
+                    Messages = ResultMessages.ToArray(),
+                    Selection = Selection,
+                    ExecutionElapsed = ExecutionElapsedTime,
+                    ExecutionStart = ExecutionStartTimeStamp,
+                    ExecutionEnd = ExecutionEndTimeStamp
+                };
+            }
+        }
+
         /// <summary>
         /// The range from the file that is this batch
         /// </summary>
@@ -169,8 +209,10 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
 
             try
             {
-                DbCommand command = null;
+                // Register the message listener to *this instance* of the batch
+                // Note: This is being done to associate messages with batches
                 ReliableSqlConnection sqlConn = conn as ReliableSqlConnection;
+                DbCommand command;
                 if (sqlConn != null)
                 {
                     // Register the message listener to *this instance* of the batch
@@ -258,6 +300,12 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
                 // Mark that we have executed
                 HasExecuted = true;
                 executionEndTime = DateTime.Now;
+
+                // Fire an event to signify that the batch has completed
+                if (BatchCompletion != null)
+                {
+                    await BatchCompletion(this);
+                }
             }
         }
 
@@ -270,6 +318,12 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         /// <returns>A subset of results</returns>
         public Task<ResultSetSubset> GetSubset(int resultSetIndex, int startRow, int rowCount)
         {
+            // Sanity check to make sure that the batch has finished
+            if (!HasExecuted)
+            {
+                throw new InvalidOperationException(SR.QueryServiceSubsetBatchNotCompleted);
+            }
+
             // Sanity check to make sure we have valid numbers
             if (resultSetIndex < 0 || resultSetIndex >= resultSets.Count)
             {