MDEV-7856: EXPLAIN FORMAT=JSON should show partitions

mysql-test/r/explain_json_format_partitions.result

+create table t2(a int);
+insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (
+a int not null
+) partition by key(a);
+insert into t1 select a from t2;
+explain partitions select * from t1 where a in (2,3,4);
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p0	ALL	NULL	NULL	NULL	NULL	10	Using where
+explain format=json select * from t1 where a in (2,3,4);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "table_name": "t1",
+      "partitions": ["p0"],
+      "access_type": "ALL",
+      "rows": 10,
+      "filtered": 100,
+      "attached_condition": "(t1.a in (2,3,4))"
+    }
+  }
+}
+analyze format=json select * from t1 where a in (2,3,4);
+ANALYZE
+{
+  "query_block": {
+    "select_id": 1,
+    "r_loops": 1,
+    "r_total_time_ms": "REPLACED",
+    "table": {
+      "table_name": "t1",
+      "partitions": ["p0"],
+      "access_type": "ALL",
+      "r_loops": 1,
+      "rows": 10,
+      "r_rows": 10,
+      "r_total_time_ms": "REPLACED",
+      "filtered": 100,
+      "r_filtered": 30,
+      "attached_condition": "(t1.a in (2,3,4))"
+    }
+  }
+}
+analyze format=json update t1 set a=a+10 where a in (2,3,4);
+ANALYZE
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "update": 1,
+      "table_name": "t1",
+      "partitions": ["p0"],
+      "access_type": "ALL",
+      "rows": 10,
+      "r_rows": 3,
+      "r_filtered": 100,
+      "using_io_buffer": 1,
+      "r_total_time_ms": "REPLACED",
+      "attached_condition": "(t1.a in (2,3,4))"
+    }
+  }
+}
+analyze format=json delete from t1 where a in (20,30,40);
+ANALYZE
+{
+  "query_block": {
+    "select_id": 1,
+    "table": {
+      "delete": 1,
+      "table_name": "t1",
+      "partitions": ["p0"],
+      "access_type": "ALL",
+      "rows": 10,
+      "r_rows": 10,
+      "r_filtered": 0,
+      "r_total_time_ms": "REPLACED",
+      "attached_condition": "(t1.a in (20,30,40))"
+    }
+  }
+}
+drop table t1,t2;

mysql-test/t/explain_json_format_partitions.test

+
+--source include/have_partition.inc
+create table t2(a int);
+insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (
+  a int not null
+) partition by key(a);
+insert into t1 select a from t2;
+explain partitions select * from t1 where a in (2,3,4);
+explain format=json select * from t1 where a in (2,3,4);
+--replace_regex /"r_total_time_ms": [0-9]*[.]?[0-9]*/"r_total_time_ms": "REPLACED"/
+analyze format=json select * from t1 where a in (2,3,4);
+--replace_regex /"r_total_time_ms": [0-9]*[.]?[0-9]*/"r_total_time_ms": "REPLACED"/
+analyze format=json update t1 set a=a+10 where a in (2,3,4);
+--replace_regex /"r_total_time_ms": [0-9]*[.]?[0-9]*/"r_total_time_ms": "REPLACED"/
+analyze format=json delete from t1 where a in (20,30,40);
+drop table t1,t2;

sql/sql_delete.cc

@@ -117,7 +117,8 @@ void Update_plan::save_explain_data_intern(MEM_ROOT *mem_root,
     partition_info *part_info;
     if ((part_info= table->part_info))
     {          
-      make_used_partitions_str(part_info, &explain->used_partitions);
+      make_used_partitions_str(mem_root, part_info, &explain->used_partitions,
+                               explain->used_partitions_list);
       explain->used_partitions_set= true;
     }
     else

sql/sql_explain.cc

@@ -37,6 +37,18 @@ Explain_query::Explain_query(THD *thd_arg, MEM_ROOT *root) :
 {
 }
 
+static void print_json_array(Json_writer *writer,
+                             const char *title, String_list &list)
+{
+  List_iterator_fast<char> it(list);
+  const char *name;
+  writer->add_member(title).start_array();
+  while ((name= it++))
+    writer->add_str(name);
+  writer->end_array();
+}
+
+
 
 Explain_query::~Explain_query()
 {
@@ -1219,17 +1231,9 @@ void add_json_keyset(Json_writer *writer, const char *elem_name,
                      String_list *keyset)
 {
   if (!keyset->is_empty())
-  {
-    List_iterator_fast<char> it(*keyset);
-    const char *name;
-    writer->add_member(elem_name).start_array();
-    while ((name= it++))
-      writer->add_str(name);
-    writer->end_array();
-  }
+    print_json_array(writer, elem_name, *keyset);
 }
 
-
 void Explain_table_access::print_explain_json(Explain_query *query,
                                               Json_writer *writer,
                                               bool is_analyze)
@@ -1252,7 +1256,10 @@ void Explain_table_access::print_explain_json(Explain_query *query,
   writer->add_member("table").start_object();
 
   writer->add_member("table_name").add_str(table_name);
-  // partitions
+
+  if (used_partitions_set)
+    print_json_array(writer, "partitions", used_partitions_list);
+
   writer->add_member("access_type").add_str(join_type_str[type]);
 
   add_json_keyset(writer, "possible_keys", &possible_keys);
@@ -1281,14 +1288,7 @@ void Explain_table_access::print_explain_json(Explain_query *query,
     parts_list= &key.key_parts_list;
 
   if (parts_list && !parts_list->is_empty())
-  {
-    List_iterator_fast<char> it(*parts_list);
-    const char *name;
-    writer->add_member("used_key_parts").start_array();
-    while ((name= it++))
-      writer->add_str(name);
-    writer->end_array();
-  }
+    print_json_array(writer, "used_key_parts", *parts_list);
 
   if (quick_info && !quick_info->is_basic())
   {
@@ -1299,14 +1299,7 @@ void Explain_table_access::print_explain_json(Explain_query *query,
   
   /* `ref` */
   if (!ref_list.is_empty())
-  {
-    List_iterator_fast<char> it(ref_list);
-    const char *str;
-    writer->add_member("ref").start_array();
-    while ((str= it++))
-      writer->add_str(str);
-    writer->end_array();
-  }
+    print_json_array(writer, "ref", ref_list);
 
   /* r_loops (not present in tabular output) */
   if (is_analyze)
@@ -1555,12 +1548,7 @@ void Explain_quick_select::print_json(Json_writer *writer)
 
     writer->add_member("key").add_str(range.get_key_name());
 
-    List_iterator_fast<char> it(range.key_parts_list);
-    const char *name;
-    writer->add_member("used_key_parts").start_array();
-    while ((name= it++))
-        writer->add_str(name);
-    writer->end_array();
+    print_json_array(writer, "used_key_parts", range.key_parts_list);
 
     writer->end_object();
   }
@@ -1845,6 +1833,10 @@ void Explain_update::print_explain_json(Explain_query *query,
     writer->add_member("delete").add_ll(1);
 
   writer->add_member("table_name").add_str(table_name);
+
+  if (used_partitions_set)
+    print_json_array(writer, "partitions", used_partitions_list);
+
   writer->add_member("access_type").add_str(join_type_str[jtype]);
 
   if (!possible_keys.is_empty())

sql/sql_explain.h

@@ -51,6 +51,9 @@ it into the slow query log.
 
 */
 
+#ifndef SQL_EXPLAIN_INCLUDED
+#define SQL_EXPLAIN_INCLUDED
+
 class String_list: public List<char>
 {
 public:
@@ -646,6 +649,7 @@ class Explain_table_access : public Sql_alloc
   /* id and 'select_type' are cared-of by the parent Explain_select */
   StringBuffer<32> table_name;
   StringBuffer<32> used_partitions;
+  String_list used_partitions_list;
   // valid with ET_USING_MRR
   StringBuffer<32> mrr_type;
   StringBuffer<32> firstmatch_table_name;
@@ -768,6 +772,7 @@ class Explain_update : public Explain_node
   const char *select_type;
 
   StringBuffer<32> used_partitions;
+  String_list used_partitions_list;
   bool used_partitions_set;
 
   bool impossible_where;
@@ -863,3 +868,4 @@ class Explain_delete: public Explain_update
 };
 
 
+#endif //SQL_EXPLAIN_INCLUDED

sql/sql_partition.cc

@@ -68,6 +68,7 @@
                                         // mysql_*_alter_copy_data
 #include "opt_range.h"                  // store_key_image_to_rec
 #include "sql_alter.h"                  // Alter_table_ctx
+#include "sql_select.h"
 
 #include <algorithm>
 using std::max;
@@ -7290,8 +7291,10 @@ void mem_alloc_error(size_t size)
 /**
   Return comma-separated list of used partitions in the provided given string.
 
+    @param      mem_root   Where to allocate following list
     @param      part_info  Partitioning info
     @param[out] parts      The resulting list of string to fill
+    @param[out] used_partitions_list result list to fill
 
     Generate a list of used partitions (from bits in part_info->read_partitions
     bitmap), and store it into the provided String object.
@@ -7302,7 +7305,10 @@ void mem_alloc_error(size_t size)
     that was written or locked.
 */
 
-void make_used_partitions_str(partition_info *part_info, String *parts_str)
+void make_used_partitions_str(MEM_ROOT *alloc,
+                              partition_info *part_info,
+                              String *parts_str,
+                              String_list &used_partitions_list)
 {
   parts_str->length(0);
   partition_element *pe;
@@ -7321,6 +7327,7 @@ void make_used_partitions_str(partition_info *part_info, String *parts_str)
         {
           if (parts_str->length())
             parts_str->append(',');
+          uint index= parts_str->length();
           parts_str->append(head_pe->partition_name,
                            strlen(head_pe->partition_name),
                            system_charset_info);
@@ -7328,6 +7335,7 @@ void make_used_partitions_str(partition_info *part_info, String *parts_str)
           parts_str->append(pe->partition_name,
                            strlen(pe->partition_name),
                            system_charset_info);
+          used_partitions_list.append_str(alloc, parts_str->ptr() + index);
         }
         partition_id++;
       }
@@ -7341,6 +7349,7 @@ void make_used_partitions_str(partition_info *part_info, String *parts_str)
       {
         if (parts_str->length())
           parts_str->append(',');
+        used_partitions_list.append_str(alloc, pe->partition_name);
         parts_str->append(pe->partition_name, strlen(pe->partition_name),
                          system_charset_info);
       }

sql/sql_partition.h

@@ -74,6 +74,7 @@ typedef struct {
   uint32 end_part;
 } part_id_range;
 
+class String_list;
 struct st_partition_iter;
 #define NOT_A_PARTITION_ID UINT_MAX32
 
@@ -114,7 +115,9 @@ bool mysql_unpack_partition(THD *thd, char *part_buf,
                             TABLE *table, bool is_create_table_ind,
                             handlerton *default_db_type,
                             bool *work_part_info_used);
-void make_used_partitions_str(partition_info *part_info, String *parts_str);
+void make_used_partitions_str(MEM_ROOT *mem_root,
+                              partition_info *part_info, String *parts_str,
+                              String_list &used_partitions_list);
 uint32 get_list_array_idx_for_endpoint(partition_info *part_info,
                                        bool left_endpoint,
                                        bool include_endpoint);

sql/sql_select.cc

@@ -23500,8 +23500,9 @@ void JOIN_TAB::save_explain_data(Explain_table_access *eta, table_map prefix_tab
     partition_info *part_info;
     if (!table->derived_select_number && 
         (part_info= table->part_info))
-    {          
-      make_used_partitions_str(part_info, &eta->used_partitions);
+    { //TODO: all thd->mem_root here should be fixed
+      make_used_partitions_str(thd->mem_root, part_info, &eta->used_partitions,
+                               eta->used_partitions_list);
       eta->used_partitions_set= true;
     }
     else

sql/sql_update.cc

@@ -517,7 +517,7 @@ int mysql_update(THD *thd,
   */
   if (thd->lex->describe)
     goto produce_explain_and_leave;
-  explain= query_plan.save_explain_update_data(thd->mem_root, thd);
+  explain= query_plan.save_explain_update_data(query_plan.mem_root, thd);
 
   ANALYZE_START_TRACKING(&explain->command_tracker);
 
@@ -1046,7 +1046,7 @@ int mysql_update(THD *thd,
     We come here for various "degenerate" query plans: impossible WHERE,
     no-partitions-used, impossible-range, etc.
   */
-  query_plan.save_explain_update_data(thd->mem_root, thd);
+  query_plan.save_explain_update_data(query_plan.mem_root, thd);
 
 emit_explain_and_leave:
   int err2= thd->lex->explain->send_explain(thd);