From c5870cbaba9f99022238ac44df60fd3ffb79b208 Mon Sep 17 00:00:00 2001
From: Johan Wikman <johan.wikman@gmail.com>
Date: Thu, 20 Aug 2020 13:04:02 +0300
Subject: [PATCH] MXS-3121 Expose statement currently being classified

Intended to be used from fatal signal handlers. As the statement will
be returned only while classification is in process, if a statement
is returned, it is an indication that the crash was caused by the
classification.
---
 include/maxscale/query_classifier.h           | 30 +++++++++++++++++++
 .../qc_mysqlembedded/qc_mysqlembedded.cc      |  9 +++++-
 query_classifier/qc_sqlite/qc_sqlite.cc       | 17 ++++++++++-
 server/core/query_classifier.cc               |  8 +++++
 4 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/include/maxscale/query_classifier.h b/include/maxscale/query_classifier.h
index 4a5c78751..41c10c98d 100644
--- a/include/maxscale/query_classifier.h
+++ b/include/maxscale/query_classifier.h
@@ -469,6 +469,19 @@ typedef struct query_classifier
      * @return QC_RESULT_OK if @c options is valid, otherwise QC_RESULT_ERROR.
      */
     int32_t (* qc_set_options)(uint32_t options);
+
+    /**
+     * Return statement currently being classified.
+     *
+     * @param ppStmp  Pointer to pointer that on return will point to the
+     *                statement being classified.
+     * @param pLen    Pointer to value that on return will contain the length
+     *                of the returned string.
+     *
+     * @return QC_RESULT_OK if a statement was returned (i.e. a statement is being
+     *         classified), QC_RESULT_ERROR otherwise.
+     */
+    int32_t (* qc_get_current_stmt)(const char** ppStmt, size_t* pLen);
 } QUERY_CLASSIFIER;
 
 /**
@@ -996,4 +1009,21 @@ uint32_t qc_get_options();
  */
 bool qc_set_options(uint32_t options);
 
+/**
+ * Return statement currently being classified.
+ *
+ * @param ppStmp  Pointer to pointer that on return will point to the
+ *                statement being classified.
+ * @param pLen    Pointer to value that on return will contain the length
+ *                of the returned string.
+ *
+ * @return True, if a statement was returned (i.e. a statement is being
+ *         classified), false otherwise.
+ *
+ * @note A string /may/ be returned /only/ when this function is called from
+ *       a signal handler that is called due to the classifier causing
+ *       a crash.
+ */
+bool qc_get_current_stmt(const char** ppStmt, size_t* pLen);
+
 MXS_END_DECLS
diff --git a/query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc b/query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc
index 4599ed0d2..7fb77fe20 100644
--- a/query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc
+++ b/query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc
@@ -3648,6 +3648,12 @@ int32_t qc_mysql_set_options(uint32_t options)
     return rv;
 }
 
+int32_t qc_mysql_get_current_stmt(const char** ppStmt, size_t* pLen)
+{
+    return QC_RESULT_ERROR;
+}
+
+
 /**
  * EXPORTS
  */
@@ -3684,7 +3690,8 @@ extern "C"
             nullptr,    // qc_info_dup not supported.
             nullptr,    // qc_info_close not supported.
             qc_mysql_get_options,
-            qc_mysql_set_options
+            qc_mysql_set_options,
+            qc_mysql_get_current_stmt
         };
 
         static MXS_MODULE info =
diff --git a/query_classifier/qc_sqlite/qc_sqlite.cc b/query_classifier/qc_sqlite/qc_sqlite.cc
index 864c48683..5ac743ccc 100644
--- a/query_classifier/qc_sqlite/qc_sqlite.cc
+++ b/query_classifier/qc_sqlite/qc_sqlite.cc
@@ -5359,6 +5359,20 @@ int32_t qc_sqlite_set_options(uint32_t options)
     return rv;
 }
 
+int32_t qc_sqlite_get_current_stmt(const char** ppStmt, size_t* pLen)
+{
+    int32_t rv = QC_RESULT_ERROR;
+
+    if (this_thread.pInfo && this_thread.pInfo->m_pQuery && (this_thread.pInfo->m_nQuery != 0))
+    {
+        *ppStmt = this_thread.pInfo->m_pQuery;
+        *pLen = this_thread.pInfo->m_nQuery;
+        rv = QC_RESULT_OK;
+    }
+
+    return rv;
+}
+
 /**
  * EXPORTS
  */
@@ -5395,7 +5409,8 @@ extern "C"
             qc_sqlite_info_dup,
             qc_sqlite_info_close,
             qc_sqlite_get_options,
-            qc_sqlite_set_options
+            qc_sqlite_set_options,
+            qc_sqlite_get_current_stmt
         };
 
         static MXS_MODULE info =
diff --git a/server/core/query_classifier.cc b/server/core/query_classifier.cc
index 14e9fda2e..425167f60 100644
--- a/server/core/query_classifier.cc
+++ b/server/core/query_classifier.cc
@@ -1313,6 +1313,14 @@ bool qc_set_options(uint32_t options)
     return rv == QC_RESULT_OK;
 }
 
+bool qc_get_current_stmt(const char** ppStmt, size_t* pLen)
+{
+    QC_TRACE();
+    mxb_assert(this_unit.classifier);
+
+    return this_unit.classifier->qc_get_current_stmt(ppStmt, pLen) == QC_RESULT_OK;
+}
+
 void qc_get_cache_properties(QC_CACHE_PROPERTIES* properties)
 {
     properties->max_size = this_unit.cache_max_size();