MDEV-6398: ANALYZE UPDATE does not populate r_rows

- In print_explain_row(), do not forget to print r_rows.
- Switch Explain_update from using its own counters to re-using
  Table_access_tracker.
- Make ANALYZE UPDATE code structure uniform with ANALYZE DELETE.

mysql-test/r/analyze_stmt.result

@@ -16,7 +16,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_f
 # ANALYZE DELETE will delete rows:
 analyze delete from t1 where a in (2,3,4);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	NULL	100.00	30.00	Using where
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	10	100.00	30.00	Using where
 select * from t1;
 a
 0
@@ -32,7 +32,7 @@ create table t1(a int, b int);
 insert into t1 select a,a from t0;
 analyze update t1 set b=100+b where a in (6,7,8);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	NULL	100.00	30.00	Using where
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	10	100.00	30.00	Using where
 select * from t1;
 a	b
 0	0
@@ -233,3 +233,12 @@ analyze update t1 set b=12345 where a > 30 and a < 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 drop table t1;
+#
+# MDEV-6398: ANALYZE UPDATE does not populate r_rows
+#
+create table t1 (i int);
+insert into t1 values (1),(2),(3),(4);
+analyze update t1 set i=8;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	4	100.00	100.00	
+drop table t1;

mysql-test/t/analyze_stmt.test

@@ -183,4 +183,11 @@ analyze update t1 set b=12345 where 1 > 2;
 analyze update t1 set b=12345 where a > 30 and a < 10;
 
 drop table t1;
+--echo #
+--echo # MDEV-6398: ANALYZE UPDATE does not populate r_rows
+--echo #
+create table t1 (i int);
+insert into t1 values (1),(2),(3),(4);
+analyze update t1 set i=8;
+drop table t1;
 

sql/sql_delete.cc

@@ -539,10 +539,12 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   }
 
   explain= (Explain_delete*)thd->lex->explain->get_upd_del_plan();
+  explain->tracker.on_scan_init();
+
   while (!(error=info.read_record(&info)) && !thd->killed &&
 	 ! thd->is_error())
   {
-    explain->on_record_read();
+    explain->tracker.on_record_read();
     if (table->vfield)
       update_virtual_fields(thd, table,
                             table->triggers ? VCOL_UPDATE_ALL :
@@ -551,7 +553,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     // thd->is_error() is tested to disallow delete row on error
     if (!select || select->skip_record(thd) > 0)
     {
-      explain->on_record_after_where();
+      explain->tracker.on_record_after_where();
       if (table->triggers &&
           table->triggers->process_triggers(thd, TRG_EVENT_DELETE,
                                             TRG_ACTION_BEFORE, FALSE))

sql/sql_explain.cc

@@ -957,7 +957,8 @@ int Explain_update::print_explain(Explain_query *query,
     Single-table DELETE commands do not do "Using temporary".
     "Using index condition" is also not possible (which is an unjustified limitation)
   */
-  double r_filtered= 100 * (r_rows?((double)r_rows_after_where/r_rows):1.0); 
+  double r_filtered= 100 * tracker.get_filtered_after_where();
+  ha_rows r_rows= tracker.get_avg_rows();
 
   print_explain_row(output, explain_flags, is_analyze,
                     1, /* id */
@@ -970,7 +971,7 @@ int Explain_update::print_explain(Explain_query *query,
                     key_len_buf.length() ? key_len_buf.c_ptr() : NULL,
                     NULL, /* 'ref' is always NULL in single-table EXPLAIN DELETE */
                     &rows,
-                    &r_rows,
+                    tracker.has_scans()? &r_rows : NULL,
                     r_filtered,
                     extra_str.c_ptr_safe());
 

sql/sql_explain.h

@@ -44,6 +44,10 @@ public:
 
     return r_filtered;
   }
+  
+  inline void on_scan_init() { r_scans++; }
+  inline void on_record_read() { r_rows++; }
+  inline void on_record_after_where() { r_rows_after_where++; }
 };
 
 
@@ -576,14 +580,8 @@ public:
   bool using_io_buffer;
 
   /* ANALYZE members and methods */
-  ha_rows r_rows;
-  ha_rows r_rows_after_where;
-  inline void on_record_read() { r_rows++; }
-  inline void on_record_after_where() { r_rows_after_where++; }
+  Table_access_tracker tracker;
 
-  Explain_update() : 
-    r_rows(0), r_rows_after_where(0)
-  {}
   virtual int print_explain(Explain_query *query, select_result_sink *output, 
                             uint8 explain_flags, bool is_analyze);
 };

sql/sql_select.cc

@@ -23131,7 +23131,15 @@ int print_explain_row(select_result_sink *result,
   
   /* 'r_rows' */
   if (is_analyze)
+  {
+    if (r_rows)
+    {
+      item_list.push_back(new Item_int(*r_rows, 
+                                       MY_INT64_NUM_DECIMAL_DIGITS));
+    }
+    else
       item_list.push_back(item_null);
+  }
 
   /* 'filtered' */
   const double filtered=100.0;

sql/sql_update.cc

@@ -725,9 +725,11 @@ int mysql_update(THD *thd,
     if all updated columns are read
   */
   can_compare_record= records_are_comparable(table);
+  explain->tracker.on_scan_init();
+
   while (!(error=info.read_record(&info)) && !thd->killed)
   {
-    explain->on_record_read();
+    explain->tracker.on_record_read();
     if (table->vfield)
       update_virtual_fields(thd, table,
                             table->triggers ? VCOL_UPDATE_ALL :
@@ -738,7 +740,7 @@ int mysql_update(THD *thd,
       if (table->file->was_semi_consistent_read())
         continue;  /* repeat the read of the same row if it still exists */
 
-      explain->on_record_after_where();
+      explain->tracker.on_record_after_where();
       store_record(table,record[1]);
       if (fill_record_n_invoke_before_triggers(thd, table, fields, values, 0,
                                                TRG_EVENT_UPDATE))
@@ -947,6 +949,7 @@ int mysql_update(THD *thd,
 
   end_read_record(&info);
   delete select;
+  select= NULL;
   THD_STAGE_INFO(thd, stage_end);
   (void) table->file->extra(HA_EXTRA_NO_IGNORE_DUP_KEY);
 
@@ -996,11 +999,7 @@ int mysql_update(THD *thd,
   id= thd->arg_of_last_insert_id_function ?
     thd->first_successful_insert_id_in_prev_stmt : 0;
 
-  if (thd->lex->analyze_stmt)
-  {
-    error= thd->lex->explain->send_explain(thd);
-  }
-  else if (error < 0)
+  if (error < 0 && !thd->lex->analyze_stmt)
   {
     char buff[MYSQL_ERRMSG_SIZE];
     my_snprintf(buff, sizeof(buff), ER(ER_UPDATE_INFO), (ulong) found,
@@ -1019,10 +1018,14 @@ int mysql_update(THD *thd,
   }
   *found_return= found;
   *updated_return= updated;
+  
+  
+  if (thd->lex->analyze_stmt)
+    goto emit_explain_and_leave;
+
   DBUG_RETURN((error >= 0 || thd->is_error()) ? 1 : 0);
 
 err:
-
   delete select;
   free_underlaid_joins(thd, select_lex);
   table->disable_keyread();
@@ -1036,6 +1039,7 @@ produce_explain_and_leave:
   */
   query_plan.save_explain_data(thd->lex->explain);
 
+emit_explain_and_leave:
   int err2= thd->lex->explain->send_explain(thd);
 
   delete select;