MDEV-5273 Prepared statement doesn't return metadata after prepare.

        The metadata creation part of the mysqld_shww_create separated
        to be used on the mysqld_stmt_prepare stage.

sql/sql_prepare.cc

@@ -103,6 +103,7 @@ When one supplies long data for a placeholder:
 #include "sql_derived.h" // mysql_derived_prepare,
                          // mysql_handle_derived
 #include "sql_cursor.h"
+#include "sql_show.h"
 #include "sp_head.h"
 #include "sp.h"
 #include "sp_cache.h"
@@ -1811,6 +1812,42 @@ static bool mysql_test_create_table(Prepared_statement *stmt)
 }
 
 
+/**
+  Validate and prepare for execution CREATE TABLE statement.
+
+  @param stmt               prepared statement
+  @param tables             list of tables used in this query
+
+  @retval
+    FALSE             success
+  @retval
+    TRUE              error, error message is set in THD
+*/
+
+static int mysql_test_show_create_table(Prepared_statement *stmt,
+                                        TABLE_LIST *tables)
+{
+  DBUG_ENTER("mysql_test_show_create_table");
+  THD *thd= stmt->thd;
+  List<Item> fields;
+  char buff[2048];
+  String buffer(buff, sizeof(buff), system_charset_info);
+
+  if (mysqld_show_create_get_fields(thd, tables, &fields, &buffer))
+    goto err_exit;
+    
+  if (send_prep_stmt(stmt, fields.elements) ||
+      thd->protocol->send_result_set_metadata(&fields, Protocol::SEND_EOF) ||
+      thd->protocol->flush())
+    goto err_exit;
+
+  DBUG_RETURN(2);
+
+err_exit:
+  DBUG_RETURN(1);
+}
+
+
 /**
   @brief Validate and prepare for execution CREATE VIEW statement
 
@@ -2144,7 +2181,14 @@ static bool check_prepared_statement(Prepared_statement *stmt)
   case SQLCOM_CREATE_TABLE:
     res= mysql_test_create_table(stmt);
     break;
-
+  case SQLCOM_SHOW_CREATE:
+    res= mysql_test_show_create_table(stmt, tables);
+    if (res == 2)
+    {
+      /* Statement and field info has already been sent */
+      DBUG_RETURN(FALSE);
+    }
+    break;
   case SQLCOM_CREATE_VIEW:
     if (lex->create_view_mode == VIEW_ALTER)
     {

sql/sql_show.cc

@@ -1092,39 +1092,29 @@ public:
 
 
 /*
-  Return CREATE command for table or view
+  Return metadata for CREATE command for table or view
 
   @param thd	     Thread handler
   @param table_list  Table / view
+  @param field_list  resulting list of fields
+  @param buffer      resulting CREATE statement
 
   @return
   @retval 0      OK
   @retval 1      Error
 
-  @notes
-  table_list->db and table_list->table_name are kept unchanged to
-  not cause problems with SP.
 */
 
 bool
-mysqld_show_create(THD *thd, TABLE_LIST *table_list)
+mysqld_show_create_get_fields(THD *thd, TABLE_LIST *table_list,
+                              List<Item> *field_list, String *buffer)
 {
-  Protocol *protocol= thd->protocol;
-  char buff[2048];
-  String buffer(buff, sizeof(buff), system_charset_info);
-  List<Item> field_list;
   bool error= TRUE;
   MEM_ROOT *mem_root= thd->mem_root;
-  DBUG_ENTER("mysqld_show_create");
+  DBUG_ENTER("mysqld_show_create_get_fields");
   DBUG_PRINT("enter",("db: %s  table: %s",table_list->db,
                       table_list->table_name));
 
-  /*
-    Metadata locks taken during SHOW CREATE should be released when
-    the statmement completes as it is an information statement.
-  */
-  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
-
   /* We want to preserve the tree for views. */
   thd->lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_VIEW;
 
@@ -1155,45 +1145,89 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list)
     goto exit;
   }
 
-  buffer.length(0);
+  buffer->length(0);
 
   if (table_list->view)
-    buffer.set_charset(table_list->view_creation_ctx->get_client_cs());
+    buffer->set_charset(table_list->view_creation_ctx->get_client_cs());
 
   if ((table_list->view ?
-       show_create_view(thd, table_list, &buffer) :
-       show_create_table(thd, table_list, &buffer, NULL, WITHOUT_DB_NAME)))
+       show_create_view(thd, table_list, buffer) :
+       show_create_table(thd, table_list, buffer, NULL, WITHOUT_DB_NAME)))
     goto exit;
 
   if (table_list->view)
   {
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "View", NAME_CHAR_LEN),
                          mem_root);
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "Create View",
-                                           MY_MAX(buffer.length(),1024)),
+                                           MY_MAX(buffer->length(),1024)),
                          mem_root);
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "character_set_client",
                                            MY_CS_NAME_SIZE),
                          mem_root);
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "collation_connection",
                                            MY_CS_NAME_SIZE),
                          mem_root);
   }
   else
   {
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "Table", NAME_CHAR_LEN),
                          mem_root);
     // 1024 is for not to confuse old clients
-    field_list.push_back(new (mem_root)
+    field_list->push_back(new (mem_root)
                          Item_empty_string(thd, "Create Table",
-                                           MY_MAX(buffer.length(),1024)),
+                                           MY_MAX(buffer->length(),1024)),
                          mem_root);
   }
+  error= FALSE;
+
+exit:
+  DBUG_RETURN(error);
+}
+
+
+/*
+  Return CREATE command for table or view
+
+  @param thd	     Thread handler
+  @param table_list  Table / view
+
+  @return
+  @retval 0      OK
+  @retval 1      Error
+
+  @notes
+  table_list->db and table_list->table_name are kept unchanged to
+  not cause problems with SP.
+*/
+
+bool
+mysqld_show_create(THD *thd, TABLE_LIST *table_list)
+{
+  Protocol *protocol= thd->protocol;
+  char buff[2048];
+  String buffer(buff, sizeof(buff), system_charset_info);
+  List<Item> field_list;
+  bool error= TRUE;
+  MEM_ROOT *mem_root= thd->mem_root;
+  DBUG_ENTER("mysqld_show_create");
+  DBUG_PRINT("enter",("db: %s  table: %s",table_list->db,
+                      table_list->table_name));
+
+  /*
+    Metadata locks taken during SHOW CREATE should be released when
+    the statmement completes as it is an information statement.
+  */
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
+
+
+  if (mysqld_show_create_get_fields(thd, table_list, &field_list, &buffer))
+    goto exit;
 
   if (protocol->send_result_set_metadata(&field_list,
                                          Protocol::SEND_NUM_ROWS |

sql/sql_show.h

@@ -85,6 +85,8 @@ bool append_identifier(THD *thd, String *packet, const char *name,
 		       uint length);
 void mysqld_list_fields(THD *thd,TABLE_LIST *table, const char *wild);
 int mysqld_dump_create_info(THD *thd, TABLE_LIST *table_list, int fd);
+bool mysqld_show_create_get_fields(THD *thd, TABLE_LIST *table_list,
+                                   List<Item> *field_list, String *buffer);
 bool mysqld_show_create(THD *thd, TABLE_LIST *table_list);
 bool mysqld_show_create_db(THD *thd, LEX_STRING *db_name,
                            LEX_STRING *orig_db_name,

tests/mysql_client_test.c

@@ -422,6 +422,15 @@ static void test_prepare_simple()
 
   mysql_stmt_close(stmt);
 
+  /* show create */
+  strmov(query, "SHOW CREATE TABLE test_prepare_simple");
+  stmt= mysql_simple_prepare(mysql, query);
+  check_stmt(stmt);
+
+  DIE_UNLESS(mysql_stmt_field_count(stmt) == 2);
+
+  mysql_stmt_close(stmt);
+
   /* now fetch the results ..*/
   rc= mysql_commit(mysql);
   myquery(rc);