Correctly handle multi-queries passed into single query API

Summary:
Prior the refactoring work on Squangle calling the single query API with a multi-query generated some sort of exception, but during the refactor this instead hit a failed CHECK() and crashed.  We had no test in our own test suite for this but a customer ran into it (https://fb.workplace.com/groups/mysql.users/posts/26881187268169867/).

Here I've modified the code to detect the situation and return an appropriate exception for the issue.  In addition I've added a test to check for this in the MySQL C++ Client to prevent regressions in the future.

Reviewed By: fadimounir

Differential Revision: D62663718

fbshipit-source-id: 72aa3c4381c7f927b5a931a01685954ec421e3df

third-party/squangle/src/squangle/mysql_client/FetchOperation.cpp

@@ -339,7 +339,11 @@ void FetchOperationImpl::actionable() {
         ++num_queries_executed_;
         no_index_used_ |= conn().getNoIndexUsed();
         was_slow_ |= conn().wasSlow();
-        op.notifyQuerySuccess(more_results);
+        if (!op.notifyQuerySuccess(more_results)) {
+          // This usually means a multi-query was passed to the single query API
+          active_fetch_action_ = FetchAction::CompleteOperation;
+          return;
+        }
       }
       current_row_stream_.reset();
     }

third-party/squangle/src/squangle/mysql_client/FetchOperation.h

@@ -302,7 +302,7 @@ class FetchOperation : public Operation {
   // store fetched data, initialize data).
   virtual void notifyInitQuery() = 0;
   virtual void notifyRowsReady() = 0;
-  virtual void notifyQuerySuccess(bool more_results) = 0;
+  virtual bool notifyQuerySuccess(bool more_results) = 0;
   virtual void notifyFailure(OperationResult result) = 0;
   virtual void notifyOperationCompleted(OperationResult result) = 0;
 

third-party/squangle/src/squangle/mysql_client/MultiQueryOperation.cpp

@@ -47,7 +47,7 @@ void MultiQueryOperation::notifyFailure(OperationResult result) {
   current_query_result_->setOperationResult(result);
 }
 
-void MultiQueryOperation::notifyQuerySuccess(bool) {
+bool MultiQueryOperation::notifyQuerySuccess(bool) {
   current_query_result_->setPartial(false);
 
   current_query_result_->setOperationResult(OperationResult::Succeeded);
@@ -70,6 +70,7 @@ void MultiQueryOperation::notifyQuerySuccess(bool) {
   query_results_.emplace_back(std::move(*current_query_result_.get()));
   current_query_result_ =
       std::make_unique<QueryResult>(current_query_result_->queryNum() + 1);
+  return true;
 }
 
 void MultiQueryOperation::notifyOperationCompleted(OperationResult result) {

third-party/squangle/src/squangle/mysql_client/MultiQueryOperation.h

@@ -90,7 +90,7 @@ class MultiQueryOperation : public FetchOperation {
  protected:
   void notifyInitQuery() override;
   void notifyRowsReady() override;
-  void notifyQuerySuccess(bool more_results) override;
+  bool notifyQuerySuccess(bool more_results) override;
   void notifyFailure(OperationResult result) override;
   void notifyOperationCompleted(OperationResult result) override;
 

third-party/squangle/src/squangle/mysql_client/MultiQueryStreamOperation.cpp

@@ -44,12 +44,13 @@ void MultiQueryStreamOperation::notifyRowsReady() {
   invokeCallback(StreamState::RowsReady);
 }
 
-void MultiQueryStreamOperation::notifyQuerySuccess(bool) {
+bool MultiQueryStreamOperation::notifyQuerySuccess(bool) {
   // Query Boundary, only for streaming to allow the user to read from the
   // connection.
   // This will allow pause in the end of the query. End of operations don't
   // allow.
   invokeCallback(StreamState::QueryEnded);
+  return true;
 }
 
 void MultiQueryStreamOperation::notifyFailure(OperationResult) {

third-party/squangle/src/squangle/mysql_client/MultiQueryStreamOperation.h

@@ -28,7 +28,7 @@ class MultiQueryStreamOperation : public FetchOperation {
 
   void notifyInitQuery() override;
   void notifyRowsReady() override;
-  void notifyQuerySuccess(bool more_results) override;
+  bool notifyQuerySuccess(bool more_results) override;
   void notifyFailure(OperationResult result) override;
   void notifyOperationCompleted(OperationResult result) override;
 

third-party/squangle/src/squangle/mysql_client/QueryOperation.cpp

@@ -44,10 +44,16 @@ void QueryOperation::notifyRowsReady() {
   }
 }
 
-void QueryOperation::notifyQuerySuccess(bool more_results) {
+bool QueryOperation::notifyQuerySuccess(bool more_results) {
   if (more_results) {
-    // Bad usage of QueryOperation, we are going to cancel the query
+    // This is the single-query API; we can't support multi-queries here, so if
+    // we have more results we need to generate an error and cancel.
+    setAsyncClientError(
+        (unsigned int)SquangleErrno::SQ_INVALID_API_USAGE,
+        "Multi-queries are not supported in this API - "
+        "use the multi-query API instead");
     cancel();
+    return false;
   }
 
   query_result_->setOperationResult(OperationResult::Succeeded);
@@ -62,6 +68,8 @@ void QueryOperation::notifyQuerySuccess(bool more_results) {
 
   // We are not going to make callback to user now since this only one query,
   // we make when we finish the operation
+
+  return true;
 }
 
 void QueryOperation::notifyFailure(OperationResult result) {

third-party/squangle/src/squangle/mysql_client/QueryOperation.h

@@ -101,7 +101,7 @@ class QueryOperation : public FetchOperation {
  protected:
   void notifyInitQuery() override;
   void notifyRowsReady() override;
-  void notifyQuerySuccess(bool more_results) override;
+  bool notifyQuerySuccess(bool more_results) override;
   void notifyFailure(OperationResult result) override;
   void notifyOperationCompleted(OperationResult result) override;