MDEV-5093, MDEV-5094:

- Make EXPLAIN {PARTITIONS,EXTENDED} {UPDATE,DELETE} work.

mysql-test/r/explain_non_select.result

@@ -138,3 +138,26 @@ i	i
 0	0
 9	9
 DROP TABLE t1;
+#
+# MDEV-5093, MDEV-5094: EXPLAIN PARTITIONS and EXPLAIN EXTENDED do not
+#  work for EXPLAIN UPDATE.
+#
+create table t1 (i int);
+explain partitions update t1 set i = 3;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	NULL	ALL	NULL	NULL	NULL	NULL	0	
+create table t2 (a int, b int) partition by hash(a) partitions 5;
+insert into t2 values (0,0),(1,1),(2,2),(3,3),(4,4);
+explain partitions update t2 set b=3 where a in (3,4);
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	p3,p4	ALL	NULL	NULL	NULL	NULL	2	Using where
+explain partitions delete from t2 where a in (3,4);
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	p3,p4	ALL	NULL	NULL	NULL	NULL	2	Using where
+explain extended update t2 set b=3 where a in (3,4);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+explain extended delete from t2 where a in (3,4);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+drop table t1,t2;

mysql-test/t/explain_non_select.test

@@ -1,6 +1,8 @@
 #
 # MariaDB tests for EXPLAIN UPDATE/DELETE.
 #
+--source include/have_partition.inc
+
 --disable_warnings
 drop table if exists t0, t1;
 --enable_warnings
@@ -115,3 +117,22 @@ INSERT INTO t1 VALUES (7),(0),(9);
 SELECT * FROM t1 INNER JOIN ( SELECT DISTINCT * FROM t1 ) AS sq ON (sq.i = t1.i);
 
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-5093, MDEV-5094: EXPLAIN PARTITIONS and EXPLAIN EXTENDED do not
+--echo #  work for EXPLAIN UPDATE.
+--echo #
+create table t1 (i int);
+explain partitions update t1 set i = 3;
+
+create table t2 (a int, b int) partition by hash(a) partitions 5;
+insert into t2 values (0,0),(1,1),(2,2),(3,3),(4,4);
+
+explain partitions update t2 set b=3 where a in (3,4);
+explain partitions delete from t2 where a in (3,4);
+
+explain extended update t2 set b=3 where a in (3,4);
+explain extended delete from t2 where a in (3,4);
+
+drop table t1,t2;
+

sql/opt_qpf.cc

@@ -796,7 +796,7 @@ int QPF_update::print_explain(QPF_query *query, select_result_sink *output,
                     1, /* id */
                     select_type,
                     table_name.c_ptr(), 
-                    // partitions,
+                    used_partitions_set? used_partitions.c_ptr() : NULL,
                     jtype,
                     possible_keys_line.length()? possible_keys_line.c_ptr(): NULL,
                     key_str.length()? key_str.c_ptr() : NULL,

sql/opt_qpf.h

@@ -454,6 +454,9 @@ public:
 
   const char *select_type;
 
+  StringBuffer<32> used_partitions;
+  bool used_partitions_set;
+
   bool impossible_where;
   StringBuffer<64> table_name;
 

sql/sql_delete.cc

@@ -40,7 +40,7 @@
 #include "records.h"                            // init_read_record,
 #include "sql_derived.h"                        // mysql_handle_list_of_derived
                                                 // end_read_record
-
+#include "sql_partition.h"       // make_used_partitions_str
 
 /*
   @brief
@@ -92,7 +92,24 @@ void Update_plan::save_qpf_intern(QPF_query *query, QPF_update *qpf)
 
   select_lex->set_explain_type(TRUE);
   qpf->select_type= select_lex->type;
-  
+  /* Partitions */
+  {
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+    partition_info *part_info;
+    if ((part_info= table->part_info))
+    {          
+      make_used_partitions_str(part_info, &qpf->used_partitions);
+      qpf->used_partitions_set= true;
+    }
+    else
+      qpf->used_partitions_set= false;
+#else
+    /* just produce empty column if partitioning is not compiled in */
+    qpf->used_partitions_set= false;
+#endif
+  }
+
+
   /* Set jtype */
   if (select && select->quick)
   {

sql/sql_select.cc

@@ -22331,7 +22331,7 @@ int print_explain_row(select_result_sink *result,
                       uint select_number,
                       const char *select_type,
                       const char *table_name,
-                      //const char *partitions, (todo)
+                      const char *partitions,
                       enum join_type jtype,
                       const char *possible_keys,
                       const char *index,
@@ -22351,7 +22351,15 @@ int print_explain_row(select_result_sink *result,
   item_list.push_back(new Item_string(table_name,
                                       strlen(table_name), cs));
   if (options & DESCRIBE_PARTITIONS)
-    item_list.push_back(item_null); // psergey-todo: produce proper value
+  {
+    if (partitions)
+    {
+      item_list.push_back(new Item_string(partitions,
+                                          strlen(partitions), cs));
+    }
+    else
+      item_list.push_back(item_null);
+  }
   
   const char *jtype_str= join_type_str[jtype];
   item_list.push_back(new Item_string(jtype_str,
@@ -22377,8 +22385,9 @@ int print_explain_row(select_result_sink *result,
   item_list.push_back(new Item_int(rows, 
                                    MY_INT64_NUM_DECIMAL_DIGITS));
   /* 'filtered' */
+  const double filtered=100.0;
   if (options & DESCRIBE_EXTENDED)
-    item_list.push_back(item_null);
+    item_list.push_back(new Item_float(filtered, 2));
   
   /* 'Extra' */
   item_list.push_back(new Item_string(extra, strlen(extra), cs));
@@ -22489,7 +22498,7 @@ void explain_append_mrr_info(QUICK_RANGE_SELECT *quick, String *res)
 
 
 ///////////////////////////////////////////////////////////////////////////////
-
+// TODO: join with make_possible_keys_line ?
 void append_possible_keys(String *str, TABLE *table, key_map possible_keys)
 {
   uint j;

sql/sql_select.h

@@ -1853,7 +1853,7 @@ int print_explain_row(select_result_sink *result,
                       uint select_number,
                       const char *select_type,
                       const char *table_name,
-                      //const char *partitions, (todo)
+                      const char *partitions,
                       enum join_type jtype,
                       const char *possible_keys,
                       const char *index,