MDEV-3798: EXPLAIN UPDATE/DELETE

- Add support for EXPLAIN INSERT.

mysql-test/r/explain_non_select.result

@@ -181,3 +181,20 @@ explain partitions update t1 set b=12345 where a in (32,33);
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No matching rows after partition pruning
 drop table t1;
+#
+# Tests for EXPLAIN INSERT ... VALUES 
+#
+create table t1 (a int, key(a));
+explain insert into t1 values (1),(2),(3);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	INSERT	t1	ALL	NULL	NULL	NULL	NULL	NULL	NULL
+insert into t1 values (1),(2),(3);
+create table t2 (a int, b int);
+explain insert into t2 values 
+(10, 1+(select max(a)   from t1)),
+(11, 1+(select max(a+1) from t1));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	INSERT	t2	ALL	NULL	NULL	NULL	NULL	NULL	NULL
+3	SUBQUERY	t1	index	NULL	a	5	NULL	3	Using index
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+drop table t1,t2;

mysql-test/t/explain_non_select.test

@@ -155,3 +155,18 @@ explain partitions delete from t1 where a in (32,33);
 explain partitions update t1 set b=12345 where a in (32,33);
 
 drop table t1;
+
+--echo #
+--echo # Tests for EXPLAIN INSERT ... VALUES 
+--echo #
+create table t1 (a int, key(a));
+explain insert into t1 values (1),(2),(3);
+insert into t1 values (1),(2),(3);
+
+create table t2 (a int, b int);
+explain insert into t2 values 
+  (10, 1+(select max(a)   from t1)),
+  (11, 1+(select max(a+1) from t1));
+
+drop table t1,t2;
+

sql/sp_head.cc

@@ -328,6 +328,10 @@ sp_get_flags_for_command(LEX *lex)
   }
   case SQLCOM_UPDATE:
   case SQLCOM_UPDATE_MULTI:
+  case SQLCOM_INSERT:
+  case SQLCOM_REPLACE:
+  case SQLCOM_REPLACE_SELECT:
+  case SQLCOM_INSERT_SELECT:
   {
     if (!lex->describe)
       flags= 0;

sql/sql_delete.cc

@@ -680,20 +680,8 @@ cleanup:
   /* Special exits */
 exit_without_my_ok:
   query_plan.save_explain_data(thd->lex->explain);
+  int err2= thd->lex->explain->send_explain(thd);
 
-  select_send *result2;
-  if (!(result2= new select_send()))
-    return 1;                               /* purecov: inspected */
-  List<Item> dummy; /* note: looked in 5.6 and they too use a dummy list like this */
-  result2->prepare(dummy, &thd->lex->unit);
-  thd->send_explain_fields(result2);
-  int err2= thd->lex->explain->print_explain(result2, thd->lex->describe);
-
-  if (err2)
-    result2->abort_result_set();
-  else
-    result2->send_eof();
-  
   delete select;
   free_underlaid_joins(thd, select_lex);
   //table->set_keyread(false);

sql/sql_explain.cc

@@ -22,9 +22,8 @@
 #include "sql_select.h"
 
 
-Explain_query::Explain_query()
+Explain_query::Explain_query() : upd_del_plan(NULL), insert_plan(NULL)
 {
-  upd_del_plan= NULL;
   operations= 0;
 }
 
@@ -32,6 +31,7 @@ Explain_query::Explain_query()
 Explain_query::~Explain_query()
 {
   delete upd_del_plan;
+  delete insert_plan;
   uint i;
   for (i= 0 ; i < unions.elements(); i++)
     delete unions.at(i);
@@ -100,18 +100,46 @@ void Explain_query::add_node(Explain_node *node)
 }
 
 
+/*
+  Send EXPLAIN output to the client.
+*/
+
+int Explain_query::send_explain(THD *thd)
+{
+  select_result *result;
+  LEX *lex= thd->lex;
+ 
+  if (!(result= new select_send()) || 
+      thd->send_explain_fields(result))
+    return 1;
+
+  int res;
+  if ((res= print_explain(result, lex->describe)))
+    result->abort_result_set();
+  else
+    result->send_eof();
+
+  return res;
+}
+
+
 /*
   The main entry point to print EXPLAIN of the entire query
 */
 
 int Explain_query::print_explain(select_result_sink *output, 
-                             uint8 explain_flags)
+                                 uint8 explain_flags)
 {
   if (upd_del_plan)
   {
     upd_del_plan->print_explain(this, output, explain_flags);
     return 0;
   }
+  else if (insert_plan)
+  {
+    insert_plan->print_explain(this, output, explain_flags);
+    return 0;
+  }
   else
   {
     /* Start printing from node with id=1 */
@@ -681,7 +709,7 @@ const char * Explain_quick_select::get_name_by_type()
       return "sort_intersect";
     default:
       DBUG_ASSERT(0);
-      return "Oops";
+      return "unknown quick select type";
   }
 }
 
@@ -809,13 +837,34 @@ int Explain_update::print_explain(Explain_query *query,
                     key_str.length()? key_str.c_ptr() : NULL,
                     key_len_str.length() ? key_len_str.c_ptr() : NULL,
                     NULL, /* 'ref' is always NULL in single-table EXPLAIN DELETE */
-                    rows,
+                    &rows,
                     extra_str.c_ptr());
 
   return print_explain_for_children(query, output, explain_flags);
 }
 
 
+int Explain_insert::print_explain(Explain_query *query, select_result_sink *output, 
+                                  uint8 explain_flags)
+{
+  const char *select_type="INSERT";
+  print_explain_row(output, explain_flags, 
+                    1, /* id */
+                    select_type,
+                    table_name.c_ptr(), 
+                    NULL, // partitions
+                    JT_ALL,
+                    NULL, // possible_keys
+                    NULL, // key
+                    NULL, // key_len
+                    NULL, // ref
+                    NULL, // rows
+                    NULL);
+
+  return print_explain_for_children(query, output, explain_flags);
+}
+
+
 void delete_explain_query(LEX *lex)
 {
   delete lex->explain;

sql/sql_explain.h

@@ -37,10 +37,16 @@ class Explain_query;
 class Explain_node : public Sql_alloc
 {
 public:
-  enum explain_node_type {EXPLAIN_UNION, EXPLAIN_SELECT, EXPLAIN_UPDATE, EXPLAIN_DELETE };
-  virtual enum explain_node_type get_type()= 0;
-
+  enum explain_node_type 
+  {
+    EXPLAIN_UNION, 
+    EXPLAIN_SELECT, 
+    EXPLAIN_UPDATE,
+    EXPLAIN_DELETE, 
+    EXPLAIN_INSERT
+  };
 
+  virtual enum explain_node_type get_type()= 0;
   virtual int get_select_id()= 0;
 
   /* 
@@ -172,8 +178,10 @@ public:
   bool using_filesort;
 };
 
-class Explain_delete;
 
+class Explain_update;
+class Explain_delete;
+class Explain_insert;
 
 /*
   Explain structure for a query (i.e. a statement).
@@ -229,14 +237,20 @@ public:
   /* Explain_delete inherits from Explain_update */
   Explain_update *upd_del_plan;
 
+  /* Query "plan" for INSERTs */
+  Explain_insert *insert_plan;
+
   /* Produce a tabular EXPLAIN output */
   int print_explain(select_result_sink *output, uint8 explain_flags);
   
+  /* Send tabular EXPLAIN to the client */
+  int send_explain(THD *thd);
+  
   /* Return tabular EXPLAIN output as a text string */
   bool print_explain_str(THD *thd, String *out_str);
 
   /* If true, at least part of EXPLAIN can be printed */
-  bool have_query_plan() { return upd_del_plan!= NULL || get_node(1) != NULL; }
+  bool have_query_plan() { return insert_plan || upd_del_plan|| get_node(1) != NULL; }
   MEM_ROOT *mem_root;
 private:
   Dynamic_array<Explain_union*> unions;
@@ -445,7 +459,7 @@ private:
 
 
 /*
-  Query Plan Footprint for single-table UPDATE. 
+  EXPLAIN structure for single-table UPDATE. 
   
   This is similar to Explain_table_access, except that it is more restrictive.
   Also, it can have UPDATE operation options, but currently there aren't any.
@@ -482,8 +496,28 @@ public:
 };
 
 
+/*
+  EXPLAIN data structure for an INSERT.
+  
+  At the moment this doesn't do much as we don't really have any query plans
+  for INSERT statements.
+*/
+
+class Explain_insert : public Explain_node
+{
+public:
+  StringBuffer<64> table_name;
+
+  enum explain_node_type get_type() { return EXPLAIN_INSERT; }
+  int get_select_id() { return 1; /* always root */ }
+
+  int print_explain(Explain_query *query, select_result_sink *output, 
+                    uint8 explain_flags);
+};
+
+
 /* 
-  Explain data of a single-table DELETE.
+  EXPLAIN data of a single-table DELETE.
 */
 
 class Explain_delete: public Explain_update

sql/sql_insert.cc

@@ -644,6 +644,36 @@ create_insert_stmt_from_insert_delayed(THD *thd, String *buf)
 }
 
 
+static void save_insert_query_plan(THD* thd, TABLE_LIST *table_list)
+{
+  Explain_insert* explain= new Explain_insert;
+  explain->table_name.append(table_list->table->alias);
+
+  thd->lex->explain->insert_plan= explain;
+  
+  /* See Update_plan::updating_a_view for details */
+  bool skip= test(table_list->view);
+
+  /* Save subquery children */
+  for (SELECT_LEX_UNIT *unit= thd->lex->select_lex.first_inner_unit();
+       unit;
+       unit= unit->next_unit())
+  {
+    if (skip)
+    {
+      skip= false;
+      continue;
+    }
+    /* 
+      Table elimination doesn't work for INSERTS, but let's still have this
+      here for consistency
+    */
+    if (!(unit->item && unit->item->eliminated))
+      explain->add_child(unit->first_select()->select_number);
+  }
+}
+
+
 /**
   INSERT statement implementation
 
@@ -660,6 +690,7 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
                   enum_duplicates duplic,
 		  bool ignore)
 {
+  bool retval= true;
   int error, res;
   bool transactional_table, joins_freed= FALSE;
   bool changed;
@@ -780,6 +811,17 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
  
   /* Restore the current context. */
   ctx_state.restore_state(context, table_list);
+  
+  if (thd->lex->unit.first_select()->optimize_unflattened_subqueries(false))
+  {
+    goto abort;
+  }
+  save_insert_query_plan(thd, table_list);
+  if (thd->lex->describe)
+  {
+    retval= 0;
+    goto exit_without_my_ok;
+  }
 
   /*
     Fill in the given fields and dump it to the table file
@@ -1128,16 +1170,19 @@ bool mysql_insert(THD *thd,TABLE_LIST *table_list,
   DBUG_RETURN(FALSE);
 
 abort:
+exit_without_my_ok:
 #ifndef EMBEDDED_LIBRARY
   if (lock_type == TL_WRITE_DELAYED)
     end_delayed_insert(thd);
 #endif
   if (table != NULL)
     table->file->ha_release_auto_increment();
+  retval= thd->lex->explain->send_explain(thd);
+
   if (!joins_freed)
     free_underlaid_joins(thd, &thd->lex->select_lex);
   thd->abort_on_warning= 0;
-  DBUG_RETURN(TRUE);
+  DBUG_RETURN(retval);
 }
 
 

sql/sql_parse.cc

@@ -3245,14 +3245,7 @@ end_with_restore_list:
       }
 
       if (!res && explain)
-      {
-        select_result *result= new select_send();
-        LEX *lex= thd->lex;
-        if (thd->send_explain_fields(result) ||
-            lex->explain->print_explain(result, lex->describe) ||
-            result->send_eof())
-          res= 1;
-      }
+        res= thd->lex->explain->send_explain(thd);
 
       /* revert changes for SP */
       MYSQL_INSERT_SELECT_DONE(res, (ulong) thd->get_row_count_func());
@@ -3341,14 +3334,7 @@ end_with_restore_list:
         else
         {
           if (explain)
-          {
-            select_result *result= new select_send();
-            LEX *lex= thd->lex;
-            if (thd->send_explain_fields(result) ||
-                lex->explain->print_explain(result, lex->describe) ||
-                result->send_eof())
-              res= 1;
-          }
+            res= thd->lex->explain->send_explain(thd);
         }
         delete result;
       }

sql/sql_select.cc

@@ -22238,7 +22238,10 @@ int print_explain_message_line(select_result_sink *result,
   if (options & DESCRIBE_EXTENDED)
     item_list.push_back(item_null);
 
-  item_list.push_back(new Item_string(message,strlen(message),cs));
+  if (message)
+    item_list.push_back(new Item_string(message,strlen(message),cs));
+  else
+    item_list.push_back(item_null);
 
   if (result->send_data(item_list))
     return 1;
@@ -22292,7 +22295,7 @@ int print_explain_row(select_result_sink *result,
                       const char *index,
                       const char *key_len,
                       const char *ref,
-                      ha_rows rows,
+                      ha_rows *rows,
                       const char *extra)
 {
   const CHARSET_INFO *cs= system_charset_info;
@@ -22337,15 +22340,24 @@ int print_explain_row(select_result_sink *result,
   item_list.push_back(item);
 
   /* 'rows' */
-  item_list.push_back(new Item_int(rows, 
-                                   MY_INT64_NUM_DECIMAL_DIGITS));
+  if (rows)
+  {
+    item_list.push_back(new Item_int(*rows, 
+                                     MY_INT64_NUM_DECIMAL_DIGITS));
+  }
+  else
+    item_list.push_back(item_null);
+
   /* 'filtered' */
   const double filtered=100.0;
   if (options & DESCRIBE_EXTENDED)
     item_list.push_back(new Item_float(filtered, 2));
   
   /* 'Extra' */
-  item_list.push_back(new Item_string(extra, strlen(extra), cs));
+  if (extra)
+    item_list.push_back(new Item_string(extra, strlen(extra), cs));
+  else
+    item_list.push_back(item_null);
 
   if (result->send_data(item_list))
     return 1;

sql/sql_select.h

@@ -1865,7 +1865,7 @@ int print_explain_row(select_result_sink *result,
                       const char *index,
                       const char *key_len,
                       const char *ref,
-                      ha_rows rows,
+                      ha_rows *rows,
                       const char *extra);
 void make_possible_keys_line(TABLE *table, key_map possible_keys, String *line);
 

sql/sql_update.cc

@@ -948,7 +948,7 @@ int mysql_update(THD *thd,
   if (!transactional_table && updated > 0)
     thd->transaction.stmt.modified_non_trans_table= TRUE;
 
-  thd->apc_target.disable(); //psergey-todo.
+  thd->apc_target.disable();
   apc_target_enabled= false;
   end_read_record(&info);
   delete select;
@@ -1035,19 +1035,8 @@ err:
 exit_without_my_ok:
   DBUG_ASSERT(!apc_target_enabled);
   query_plan.save_explain_data(thd->lex->explain);
-  
-  select_send *result;
-  if (!(result= new select_send()))
-    return 1;                               /* purecov: inspected */
-  List<Item> dummy; /* note: looked in 5.6 and they too use a dummy list like this */
-  result->prepare(dummy, &thd->lex->unit);
-  thd->send_explain_fields(result);
-  int err2= thd->lex->explain->print_explain(result,
-                                                          thd->lex->describe);
-  if (err2)
-    result->abort_result_set();
-  else
-    result->send_eof();
+
+  int err2= thd->lex->explain->send_explain(thd);
 
   delete select;
   free_underlaid_joins(thd, select_lex);