MDEV-39538: Different costs when same range is read twice

mysql-test/main/opt_context_load_stats_basic.result

@@ -343,7 +343,7 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].name');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "name" element not present at offset 1387.
+Warning	4253	Failed to parse saved optimizer context: "name" element not present at offset 1441.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].ddl');
 select * from t1 where a > 10;
 a	b
@@ -354,12 +354,12 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1380.
+Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1434.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].file_stat_records');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1380.
+Warning	4253	Failed to parse saved optimizer context: "file_stat_records" element not present at offset 1434.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0].index_name');
 select * from t1 where a > 10;
 a	b
@@ -374,32 +374,37 @@ set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_rang
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 621.
+Warning	4253	Failed to parse saved optimizer context: "index_name" element not present at offset 639.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].ranges');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "ranges" element not present at offset 613.
+Warning	4253	Failed to parse saved optimizer context: "ranges" element not present at offset 631.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].num_rows');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "num_rows" element not present at offset 631.
+Warning	4253	Failed to parse saved optimizer context: "num_rows" element not present at offset 649.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].cost');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "cost" element not present at offset 415.
+Warning	4253	Failed to parse saved optimizer context: "cost" element not present at offset 433.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].max_index_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 624.
+Warning	4253	Failed to parse saved optimizer context: "max_index_blocks" element not present at offset 642.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].max_row_blocks');
 select * from t1 where a > 10;
 a	b
 Warnings:
-Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 626.
+Warning	4253	Failed to parse saved optimizer context: "max_row_blocks" element not present at offset 644.
+set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].call_number');
+select * from t1 where a > 10;
+a	b
+Warnings:
+Warning	4253	Failed to parse saved optimizer context: "call_number" element not present at offset 647.
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0]');
 select * from t1 where a > 10;
 a	b

mysql-test/main/opt_context_load_stats_basic.test

@@ -253,6 +253,9 @@ select * from t1 where a > 10;
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].max_row_blocks');
 select * from t1 where a > 10;
 
+set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].list_ranges[0].call_number');
+select * from t1 where a > 10;
+
 set @opt_context=json_remove(@saved_opt_context_1, '$.list_contexts[0].indexes[0]');
 select * from t1 where a > 10;
 

mysql-test/main/opt_context_replay_basic.result

@@ -409,4 +409,130 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	4	Using where
 set optimizer_replay_context='';
 drop table t1;
+#
+# MDEV-39538: Different cost when same rangeis read twice
+#
+create table t1 (pk int primary key, a datetime, c int, key(a));
+insert into t1 (pk,a,c) values (1,'2009-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (2,'2009-11-29 03:23:32', 2);
+insert into t1 (pk,a,c) values (3,'2009-10-16 05:56:32', 2);
+insert into t1 (pk,a,c) values (4,'2010-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (5,'2010-10-16 05:56:32', 2);
+insert into t1 (pk,a,c) values (6,'2011-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (7,'2012-10-16 05:56:32', 2);
+set optimizer_record_context=1;
+explain format=json select * from t1
+where year(a) = 2010 and c < (select count(*) from t1 where year(a) = 2010);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "cost": 0.003808422,
+    "nested_loop": [
+      {
+        "table": {
+          "table_name": "t1",
+          "access_type": "range",
+          "possible_keys": ["a"],
+          "key": "a",
+          "key_length": "6",
+          "used_key_parts": ["a"],
+          "loops": 1,
+          "rows": 2,
+          "cost": 0.003808422,
+          "filtered": 100,
+          "index_condition": "t1.a between '2010-01-01 00:00:00' and '2010-12-31 23:59:59'",
+          "attached_condition": "t1.c < (subquery#2)"
+        }
+      }
+    ],
+    "subqueries": [
+      {
+        "query_block": {
+          "select_id": 2,
+          "cost": 0.001617224,
+          "nested_loop": [
+            {
+              "table": {
+                "table_name": "t1",
+                "access_type": "range",
+                "possible_keys": ["a"],
+                "key": "a",
+                "key_length": "6",
+                "used_key_parts": ["a"],
+                "loops": 1,
+                "rows": 2,
+                "cost": 0.001617224,
+                "filtered": 100,
+                "attached_condition": "t1.a between '2010-01-01 00:00:00' and '2010-12-31 23:59:59'",
+                "using_index": true
+              }
+            }
+          ]
+        }
+      }
+    ]
+  }
+}
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+set optimizer_record_context=0;
+drop table t1;
+set optimizer_replay_context='opt_context';
+# Same query as above, must have same explain cost:
+explain format=json select * from t1
+where year(a) = 2010 and c < (select count(*) from t1 where year(a) = 2010);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "cost": 0.003808422,
+    "nested_loop": [
+      {
+        "table": {
+          "table_name": "t1",
+          "access_type": "range",
+          "possible_keys": ["a"],
+          "key": "a",
+          "key_length": "6",
+          "used_key_parts": ["a"],
+          "loops": 1,
+          "rows": 2,
+          "cost": 0.003808422,
+          "filtered": 100,
+          "index_condition": "t1.a between '2010-01-01 00:00:00' and '2010-12-31 23:59:59'",
+          "attached_condition": "t1.c < (subquery#2)"
+        }
+      }
+    ],
+    "subqueries": [
+      {
+        "query_block": {
+          "select_id": 2,
+          "cost": 0.001617224,
+          "nested_loop": [
+            {
+              "table": {
+                "table_name": "t1",
+                "access_type": "range",
+                "possible_keys": ["a"],
+                "key": "a",
+                "key_length": "6",
+                "used_key_parts": ["a"],
+                "loops": 1,
+                "rows": 2,
+                "cost": 0.001617224,
+                "filtered": 100,
+                "attached_condition": "t1.a between '2010-01-01 00:00:00' and '2010-12-31 23:59:59'",
+                "using_index": true
+              }
+            }
+          ]
+        }
+      }
+    ]
+  }
+}
+set optimizer_replay_context='';
+drop table t1;
 drop database db1;

mysql-test/main/opt_context_replay_basic.test

@@ -200,4 +200,39 @@ set optimizer_replay_context='';
 --remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
 drop table t1;
 
+--echo #
+--echo # MDEV-39538: Different cost when same rangeis read twice
+--echo #
+create table t1 (pk int primary key, a datetime, c int, key(a));
+
+insert into t1 (pk,a,c) values (1,'2009-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (2,'2009-11-29 03:23:32', 2);
+insert into t1 (pk,a,c) values (3,'2009-10-16 05:56:32', 2);
+insert into t1 (pk,a,c) values (4,'2010-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (5,'2010-10-16 05:56:32', 2);
+insert into t1 (pk,a,c) values (6,'2011-11-29 13:43:32', 2);
+insert into t1 (pk,a,c) values (7,'2012-10-16 05:56:32', 2);
+
+set optimizer_record_context=1;
+explain format=json select * from t1
+  where year(a) = 2010 and c < (select count(*) from t1 where year(a) = 2010);
+select context into dumpfile "../../tmp/dump1.sql"
+from information_schema.optimizer_context;
+set optimizer_record_context=0;
+drop table t1;
+--disable_query_log
+--disable_result_log
+--source "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+--enable_query_log
+--enable_result_log
+set optimizer_replay_context='opt_context';
+--echo # Same query as above, must have same explain cost:
+explain format=json select * from t1
+  where year(a) = 2010 and c < (select count(*) from t1 where year(a) = 2010);
+
+set optimizer_replay_context='';
+--remove_file "$MYSQLTEST_VARDIR/tmp/dump1.sql"
+drop table t1;
+
+
 drop database db1;

sql/opt_context_store_replay.cc

@@ -112,6 +112,7 @@ class Multi_range_read_const_call_record : public Sql_alloc
   Cost_estimate cost;
   ha_rows max_index_blocks;
   ha_rows max_row_blocks;
+  ulong call_number;
 };
 
 /*
@@ -257,6 +258,7 @@ void dump_mrr_info_calls(List<Multi_range_read_const_call_record> *mrr_list,
 
     irc_wrapper.add("max_index_blocks", irc->max_index_blocks);
     irc_wrapper.add("max_row_blocks", irc->max_row_blocks);
+    irc_wrapper.add("call_number", irc->call_number);
   }
 }
 
@@ -818,11 +820,13 @@ void Optimizer_context_recorder::record_multi_range_read_info_const(
   if (current_thd->lex->explain->is_query_plan_ready())
     return;
 
+  mrr_counter++;
   auto *range_ctx= new (mem_root) Multi_range_read_const_call_record;
 
   if (unlikely(!range_ctx))
     return; // OOM
 
+  range_ctx->call_number= mrr_counter;
   const char *index_name= tbl->table->key_info[keynr].name.str;
   if (!(range_ctx->idx_name= strdup_root(mem_root, index_name)))
     return; // OOM
@@ -1285,8 +1289,7 @@ static int parse_range_context(MEM_ROOT *mem_root, json_engine_t *je, String *er
   Read_named_member array[]= {
       {"index_name", Read_string(mem_root, &out->idx_name), false},
       {"ranges", Read_array_of_strings(mem_root, &out->range_list), false},
-      {"num_rows",
-       Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->rows),
+      {"num_rows", Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->rows),
        false},
       {"cost", Read_range_cost_estimate(mem_root, &out->cost), false},
       {"max_index_blocks",
@@ -1295,6 +1298,8 @@ static int parse_range_context(MEM_ROOT *mem_root, json_engine_t *je, String *er
       {"max_row_blocks",
        Read_non_neg_integer<ha_rows, ULONGLONG_MAX>(&out->max_row_blocks),
        false},
+      {"call_number",
+       Read_non_neg_integer<ulong, ULONG_MAX>(&out->call_number), false},
       {NULL, Read_double(NULL), true}};
 
   return parse_context_obj_from_json_array(je, err_buf, err_msg, array);
@@ -1516,6 +1521,7 @@ bool Optimizer_context_replay::infuse_range_stats(
   if (!has_records() || !is_base_table(table->pos_in_table_list))
     return true;
 
+  mrr_counter++;
   KEY *keyinfo= table->key_info + keynr;
   const char *idx_name= keyinfo->name.str;
   const KEY_PART_INFO *key_part= keyinfo->key_part;
@@ -1544,6 +1550,9 @@ bool Optimizer_context_replay::infuse_range_stats(
     List_iterator<Multi_range_read_const_call_record> range_ctx_itr(mrr_const_calls);
     while (Multi_range_read_const_call_record *range_ctx= range_ctx_itr++)
     {
+      if (range_ctx->call_number != mrr_counter)
+        continue;
+
       List_iterator<char> range_itr(range_ctx->range_list);
       seq_it= seq_if->init((void *) seq, 0, 0);
       bool matched= true;

sql/opt_context_store_replay.h

@@ -88,9 +88,12 @@ class Optimizer_context_recorder
   table_context_for_store *get_table_context(const TABLE_LIST *tbl);
   static const uchar *get_tbl_ctx_key(const void *entry_, size_t *length,
                                       my_bool flags);
+  /*
+    counter that tracks record_multi_range_read_info_const() calls
+  */
+  ulong mrr_counter= 0;
 };
 
-
 /* Save the collected context into optimizer_context IS table */
 bool store_optimizer_context(THD *thd);
 
@@ -150,6 +153,10 @@ class Optimizer_context_replay
   bool infuse_table_rows(const TABLE *tbl, ha_rows *rows);
 
   THD *thd;
+  /*
+    counter that tracks infuse_range_stats() calls
+  */
+  ulong mrr_counter= 0;
   /*
     Statistics that tables had before we've replaced them with values from
     the saved context. To be used to restore the original values.