From 83123412f00d9b69f1c5ea39b160d1d27be701a9 Mon Sep 17 00:00:00 2001
From: Oleksandr Byelkin <sanja@mariadb.com>
Date: Wed, 18 Apr 2018 19:34:12 +0200
Subject: MDEV-11975: SQLCOM_PREPARE of EXPLAIN & ANALYZE statement do not
 return correct metadata info

Added metadate info after prepare EXPLAIN/ANALYZE.
---
 sql/sql_class.cc   | 29 +++++++++++++++++++++--------
 sql/sql_class.h    |  2 ++
 sql/sql_prepare.cc | 24 ++++++++++++++++++++++--
 3 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 0971d4fdaaa..628dcee0570 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -2405,18 +2405,31 @@ CHANGED_TABLE_LIST* THD::changed_table_dup(const char *key, long key_length)
 }
 
 
-int THD::send_explain_fields(select_result *result, uint8 explain_flags, bool is_analyze)
+void THD::prepare_explain_fields(select_result *result,
+                                 List<Item> *field_list,
+                                 uint8 explain_flags,
+                                 bool is_analyze)
 {
-  List<Item> field_list;
   if (lex->explain_json)
-    make_explain_json_field_list(field_list, is_analyze);
+    make_explain_json_field_list(*field_list, is_analyze);
   else
-    make_explain_field_list(field_list, explain_flags, is_analyze);
+    make_explain_field_list(*field_list, explain_flags, is_analyze);
+
+  result->prepare(*field_list, NULL);
+}
 
-  result->prepare(field_list, NULL);
-  return (result->send_result_set_metadata(field_list,
-                                           Protocol::SEND_NUM_ROWS | 
-                                           Protocol::SEND_EOF));
+
+int THD::send_explain_fields(select_result *result,
+                             uint8 explain_flags,
+                             bool is_analyze)
+{
+  List<Item> field_list;
+  int rc;
+  prepare_explain_fields(result, &field_list, explain_flags, is_analyze);
+  rc= result->send_result_set_metadata(field_list,
+                                       Protocol::SEND_NUM_ROWS |
+                                       Protocol::SEND_EOF);
+  return(rc);
 }
 
 
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 8dde68b7fba..e93bd00eec0 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -3331,6 +3331,8 @@ public:
   void add_changed_table(TABLE *table);
   void add_changed_table(const char *key, long key_length);
   CHANGED_TABLE_LIST * changed_table_dup(const char *key, long key_length);
+  void prepare_explain_fields(select_result *result, List<Item> *field_list,
+                              uint8 explain_flags, bool is_analyze);
   int send_explain_fields(select_result *result, uint8 explain_flags,
                           bool is_analyze);
   void make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index 455d6b3cb86..89b7e490cb9 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -2475,8 +2475,28 @@ static bool check_prepared_statement(Prepared_statement *stmt)
     break;
   }
   if (res == 0)
-    DBUG_RETURN(stmt->is_sql_prepare() ?
-                FALSE : (send_prep_stmt(stmt, 0) || thd->protocol->flush()));
+  {
+    if (!stmt->is_sql_prepare())
+    {
+       if (lex->describe || lex->analyze_stmt)
+       {
+         if (!lex->result &&
+             !(lex->result= new (stmt->mem_root) select_send(thd)))
+              DBUG_RETURN(TRUE);
+         List<Item> field_list;
+         thd->prepare_explain_fields(lex->result, &field_list,
+                                     lex->describe, lex->analyze_stmt);
+         res= send_prep_stmt(stmt, lex->result->field_count(field_list)) ||
+              lex->result->send_result_set_metadata(field_list,
+                                                    Protocol::SEND_EOF);
+       }
+       else
+         res= send_prep_stmt(stmt, 0);
+       if (!res)
+         thd->protocol->flush();
+    }
+    DBUG_RETURN(FALSE);
+  }
 error:
   DBUG_RETURN(TRUE);
 }
-- 
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