MDEV-3798: EXPLAIN UPDATE/DELETE

- Better EXPLAIN-saving methods for quick selects

sql/opt_range.cc

@@ -11940,110 +11940,134 @@ void QUICK_SELECT_I::add_key_name(String *str, bool *first)
 }
  
 
-void QUICK_RANGE_SELECT::save_info(MEM_ROOT *alloc,
-                                   Explain_quick_select *explain)
+Explain_quick_select* QUICK_RANGE_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= QS_TYPE_RANGE;
-  explain->range.set(alloc, head->key_info[index].name, max_used_key_length);
+  Explain_quick_select *res;
+  if ((res= new (alloc) Explain_quick_select(QS_TYPE_RANGE)))
+    res->range.set(alloc, head->key_info[index].name, max_used_key_length);
+  return res;
 }
 
 
-void QUICK_GROUP_MIN_MAX_SELECT::save_info(MEM_ROOT *alloc, 
-                                           Explain_quick_select *explain)
+Explain_quick_select* QUICK_GROUP_MIN_MAX_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= QS_TYPE_GROUP_MIN_MAX;
-  explain->range.set(alloc, head->key_info[index].name, max_used_key_length);
+  Explain_quick_select *res;
+  if ((res= new (alloc) Explain_quick_select(QS_TYPE_GROUP_MIN_MAX)))
+    res->range.set(alloc, head->key_info[index].name, max_used_key_length);
+  return res;
 }
 
 
-void QUICK_INDEX_SORT_SELECT::save_info(MEM_ROOT *alloc, 
-                                        Explain_quick_select *explain)
+Explain_quick_select* QUICK_INDEX_SORT_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= get_type();
+  Explain_quick_select *res;
+  if (!(res= new (alloc) Explain_quick_select(get_type())))
+    return NULL;
 
   QUICK_RANGE_SELECT *quick;
-  Explain_quick_select *child_qpf;
+  Explain_quick_select *child_explain;
   List_iterator_fast<QUICK_RANGE_SELECT> it(quick_selects);
   while ((quick= it++))
   {
-    child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    quick->save_info(alloc, child_qpf);
+    if ((child_explain= quick->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
 
   if (pk_quick_select)
   {
-    child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    pk_quick_select->save_info(alloc, child_qpf);
+    if ((child_explain= pk_quick_select->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
+  return res;
 }
 
+
 /*
-  Same as QUICK_INDEX_SORT_SELECT::save_info(), but primary key is printed
+  Same as QUICK_INDEX_SORT_SELECT::get_explain(), but primary key is printed
   first
 */
-void QUICK_INDEX_INTERSECT_SELECT::save_info(MEM_ROOT *alloc, 
-                                             Explain_quick_select *explain)
+
+Explain_quick_select* QUICK_INDEX_INTERSECT_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= get_type();
-  Explain_quick_select *child_qpf;
+  Explain_quick_select *res;
+  Explain_quick_select *child_explain;
+
+  if (!(res= new (alloc) Explain_quick_select(get_type())))
+    return NULL;
 
   if (pk_quick_select)
   {
-    child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    pk_quick_select->save_info(alloc, child_qpf);
+    if ((child_explain= pk_quick_select->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
 
   QUICK_RANGE_SELECT *quick;
   List_iterator_fast<QUICK_RANGE_SELECT> it(quick_selects);
   while ((quick= it++))
   {
-    child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    quick->save_info(alloc, child_qpf);
+    if ((child_explain= quick->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
-
+  return res;
 }
 
 
-void QUICK_ROR_INTERSECT_SELECT::save_info(MEM_ROOT *alloc, 
-                                           Explain_quick_select *explain)
+Explain_quick_select* QUICK_ROR_INTERSECT_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= get_type();
+  Explain_quick_select *res;
+  Explain_quick_select *child_explain;
+
+  if (!(res= new (alloc) Explain_quick_select(get_type())))
+    return NULL;
 
   QUICK_SELECT_WITH_RECORD *qr;
   List_iterator_fast<QUICK_SELECT_WITH_RECORD> it(quick_selects);
   while ((qr= it++))
   {
-    Explain_quick_select *child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    qr->quick->save_info(alloc, child_qpf);
+    if ((child_explain= qr->quick->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
 
   if (cpk_quick)
   {
-    Explain_quick_select *child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    cpk_quick->save_info(alloc, child_qpf);
+    if ((child_explain= cpk_quick->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
+  return res;
 }
 
 
-void QUICK_ROR_UNION_SELECT::save_info(MEM_ROOT *alloc, 
-                                       Explain_quick_select *explain)
+Explain_quick_select* QUICK_ROR_UNION_SELECT::get_explain(MEM_ROOT *alloc)
 {
-  explain->quick_type= get_type();
+  Explain_quick_select *res;
+  Explain_quick_select *child_explain;
+
+  if (!(res= new (alloc) Explain_quick_select(get_type())))
+    return NULL;
 
   QUICK_SELECT_I *quick;
   List_iterator_fast<QUICK_SELECT_I> it(quick_selects);
   while ((quick= it++))
   {
-    Explain_quick_select *child_qpf= new Explain_quick_select;
-    explain->children.push_back(child_qpf);
-    quick->save_info(alloc, child_qpf);
+    if ((child_explain= quick->get_explain(alloc)))
+      res->children.push_back(child_explain);
+    else
+      return NULL;
   }
+
+  return res;
 }
 
 

sql/opt_range.h

@@ -346,7 +346,7 @@ class QUICK_SELECT_I
   void add_key_name(String *str, bool *first);
 
   /* Save information about quick select's query plan */
-  virtual void save_info(MEM_ROOT *alloc, Explain_quick_select *explain)= 0;
+  virtual Explain_quick_select* get_explain(MEM_ROOT *alloc)= 0;
 
   /*
     Return 1 if any index used by this quick select
@@ -473,7 +473,7 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
   { file->position(record); }
   int get_type() { return QS_TYPE_RANGE; }
   void add_keys_and_lengths(String *key_names, String *used_lengths);
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
 #endif
@@ -610,7 +610,7 @@ class QUICK_INDEX_SORT_SELECT : public QUICK_SELECT_I
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
 #endif
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
 
   bool push_quick_back(QUICK_RANGE_SELECT *quick_sel_range);
 
@@ -674,7 +674,7 @@ class QUICK_INDEX_INTERSECT_SELECT : public QUICK_INDEX_SORT_SELECT
   int get_next();
   int get_type() { return QS_TYPE_INDEX_INTERSECT; }
   void add_keys_and_lengths(String *key_names, String *used_lengths);
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
 };
 
 
@@ -712,7 +712,7 @@ class QUICK_ROR_INTERSECT_SELECT : public QUICK_SELECT_I
   bool unique_key_range() { return false; }
   int get_type() { return QS_TYPE_ROR_INTERSECT; }
   void add_keys_and_lengths(String *key_names, String *used_lengths);
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
   bool is_keys_used(const MY_BITMAP *fields);
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
@@ -791,7 +791,7 @@ class QUICK_ROR_UNION_SELECT : public QUICK_SELECT_I
   bool unique_key_range() { return false; }
   int get_type() { return QS_TYPE_ROR_UNION; }
   void add_keys_and_lengths(String *key_names, String *used_lengths);
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
   bool is_keys_used(const MY_BITMAP *fields);
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
@@ -940,7 +940,7 @@ class QUICK_GROUP_MIN_MAX_SELECT : public QUICK_SELECT_I
 #endif
   bool is_agg_distinct() { return have_agg_distinct; }
   bool loose_scan_is_scanning() { return is_index_scan; }
-  void save_info(MEM_ROOT *alloc, Explain_quick_select *explain);
+  Explain_quick_select *get_explain(MEM_ROOT *alloc);
 };
 
 

sql/sql_explain.h

@@ -341,7 +341,10 @@ class Explain_index_use : public Sql_alloc
 class Explain_quick_select : public Sql_alloc
 {
 public:
-  int quick_type;
+  Explain_quick_select(int quick_type_arg) : quick_type(quick_type_arg) 
+  {}
+
+  const int quick_type;
   
   /* This is used when quick_type == QUICK_SELECT_I::QS_TYPE_RANGE */
   Explain_index_use range;

sql/sql_select.cc

@@ -22657,8 +22657,7 @@ int JOIN::save_explain_data(Explain_query *output, bool need_tmp_table,
       */
       if (tab->select && tab->select->quick && tab_type != JT_CONST)
       {
-        eta->quick_info= new Explain_quick_select;
-        tab->select->quick->save_info(thd->mem_root, eta->quick_info);
+        eta->quick_info= tab->select->quick->get_explain(thd->mem_root);
       }
 
       if (key_info) /* 'index' or 'ref' access */