MDEV-25008 Estimate outer_lookup_keys later in mysql_delete and mysql_update

This helps make better choice of materialization vs in-to-exists

mysql-test/main/update.result

@@ -801,3 +801,42 @@ DROP FUNCTION f1;
 DROP FUNCTION f2;
 DROP TABLE t1;
 # End of MariaDB 10.10 tests
+#
+# MDEV-25008: Delete query gets stuck on mariadb, same query works
+#             on MySQL 8.0.21
+#
+CREATE TABLE t1 (
+id int NOT NULL PRIMARY KEY,
+item_id varchar(100),
+seller_name varchar(400),
+variant varchar(400),
+FULLTEXT KEY t1_serial_IDX (item_id,seller_name,variant)
+)engine=innodb;
+insert into t1 select seq,seq,seq,seq from seq_1_to_10000;
+explain
+DELETE FROM t1 WHERE id NOT IN
+(SELECT m FROM (SELECT max(id) m FROM t1 GROUP BY item_id, seller_name, variant) AS innertable);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	#	Using where
+2	MATERIALIZED	<derived3>	ALL	NULL	NULL	NULL	NULL	#	
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	#	Using temporary; Using filesort
+explain
+UPDATE t1 SET item_id="foo" WHERE id NOT IN
+(SELECT m FROM (SELECT max(id) m FROM t1 GROUP BY item_id, seller_name, variant) AS innertable);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	#	Using where
+2	MATERIALIZED	<derived3>	ALL	NULL	NULL	NULL	NULL	#	
+3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	#	Using temporary; Using filesort
+drop table t1;
+create table t1 (a int primary key, b int, c int, key(b));
+insert into t1 select seq, seq, seq from seq_1_to_20000;
+create table t2 as select * from t1;
+explain delete from t1  where    b <= 2 and a not in (select b from t2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	b	b	5	NULL	2	Using where
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	20000	Using where
+explain delete from t1  where    b <= 3 and a not in (select b from t2);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	range	b	b	5	NULL	3	Using where
+2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	20000	
+drop table t1, t2;

mysql-test/main/update.test

@@ -743,3 +743,44 @@ DROP TABLE t1;
 --enable_ps2_protocol
 
 --echo # End of MariaDB 10.10 tests
+
+--echo #
+--echo # MDEV-25008: Delete query gets stuck on mariadb, same query works
+--echo #             on MySQL 8.0.21
+--echo #
+
+--source include/have_innodb.inc
+--source include/have_sequence.inc
+
+# original case
+CREATE TABLE t1 (
+  id int NOT NULL PRIMARY KEY,
+  item_id varchar(100),
+  seller_name varchar(400),
+  variant varchar(400),
+  FULLTEXT KEY t1_serial_IDX (item_id,seller_name,variant)
+)engine=innodb;
+
+insert into t1 select seq,seq,seq,seq from seq_1_to_10000;
+
+# Masking the `rows` column as the value might vary a bit
+--replace_column 9 #
+explain
+DELETE FROM t1 WHERE id NOT IN
+  (SELECT m FROM (SELECT max(id) m FROM t1 GROUP BY item_id, seller_name, variant) AS innertable);
+
+# Masking the `rows` column as the value might vary a bit
+--replace_column 9 #
+explain
+UPDATE t1 SET item_id="foo" WHERE id NOT IN
+  (SELECT m FROM (SELECT max(id) m FROM t1 GROUP BY item_id, seller_name, variant) AS innertable);
+
+drop table t1;
+
+# example of not full table
+create table t1 (a int primary key, b int, c int, key(b));
+insert into t1 select seq, seq, seq from seq_1_to_20000;
+create table t2 as select * from t1;
+explain delete from t1  where    b <= 2 and a not in (select b from t2);
+explain delete from t1  where    b <= 3 and a not in (select b from t2);
+drop table t1, t2;

sql/opt_range.cc

@@ -2663,9 +2663,7 @@ static int fill_used_fields_bitmap(PARAM *param)
 
     In the table struct the following information is updated:
       quick_keys           - Which keys can be used
-      quick_rows           - How many rows the key matches
-      opt_range_condition_rows - E(# rows that will satisfy the table
-                                 condition)
+      opt_range_condition_rows - E(# rows that will satisfy the table condition)
 
   IMPLEMENTATION
     opt_range_condition_rows value is obtained as follows:

sql/opt_subselect.cc

@@ -6803,15 +6803,15 @@ bool JOIN::choose_subquery_plan(table_map join_tables)
                                               &dummy,
                                               &outer_lookup_keys);
     }
+    /*
+      In case of a DELETE or UPDATE, get number of scanned rows as an
+      (upper bound) estimate of how many times the subquery will be
+      executed.
+    */
+    else if (outer_join && outer_join->sql_cmd_dml)
+      outer_lookup_keys= (double) outer_join->sql_cmd_dml->get_scanned_rows();
     else
-    {
-      /*
-        TODO: outer_join can be NULL for DELETE statements.
-        How to compute its cost?
-      */
       outer_lookup_keys= 1;
-    }
-
     /*
       B. Estimate the cost and number of records of the subquery both
       unmodified, and with injected IN->EXISTS predicates.

sql/sql_cmd.h

@@ -329,10 +329,12 @@ class Sql_cmd_dml : public Sql_cmd
 
   select_result *get_result() { return result; }
 
+  my_off_t get_scanned_rows() { return scanned_rows; }
+
 protected:
   Sql_cmd_dml()
       : Sql_cmd(), lex(nullptr), result(nullptr),
-        m_empty_query(false)
+        m_empty_query(false), scanned_rows(0)
   {}
 
   /**
@@ -399,6 +401,7 @@ class Sql_cmd_dml : public Sql_cmd
   LEX *lex;              /**< Pointer to LEX for this statement */
   select_result *result; /**< Pointer to object for handling of the result */
   bool m_empty_query;    /**< True if query will produce no rows */
+  my_off_t scanned_rows; /**< Number of scanned rows */
 };
 
 

sql/sql_delete.cc

@@ -388,8 +388,13 @@ bool Sql_cmd_delete::delete_from_single_table(THD *thd)
 
   thd->lex->promote_select_describe_flag_if_needed();
 
-  /* Apply the IN=>EXISTS transformation to all subqueries and optimize them. */
-  if (select_lex->optimize_unflattened_subqueries(false))
+  /*
+    It is too early to choose subquery optimization strategies without
+    an estimate of how many times the subquery will be executed so we
+    call optimize_unflattened_subqueries() with const_only= true, and
+    apply materialization / in-to-exists later.
+  */
+  if (select_lex->optimize_unflattened_subqueries(true))
     DBUG_RETURN(TRUE);
 
   const_cond= (!conds || conds->const_item());
@@ -517,6 +522,8 @@ bool Sql_cmd_delete::delete_from_single_table(THD *thd)
       goto produce_explain_and_leave;
 
     delete select;
+    if (select_lex->optimize_unflattened_subqueries(false))
+      DBUG_RETURN(TRUE);
     free_underlaid_joins(thd, select_lex);
     /* 
       Error was already created by quick select evaluation (check_quick()).
@@ -556,7 +563,16 @@ bool Sql_cmd_delete::delete_from_single_table(THD *thd)
   if (options & OPTION_QUICK)
     (void) table->file->extra(HA_EXTRA_QUICK);
 
-  query_plan.scanned_rows= select? select->records: table->file->stats.records;
+  /*
+    Estimate the number of scanned rows and have it accessible in
+    JOIN::choose_subquery_plan() from the outer join through
+    JOIN::sql_cmd_dml
+  */
+  scanned_rows= query_plan.scanned_rows= select ?
+    select->records : table->file->stats.records;
+  select_lex->join->sql_cmd_dml= (Sql_cmd_dml *) this;
+  if (select_lex->optimize_unflattened_subqueries(false))
+    DBUG_RETURN(TRUE);
   if (order)
   {
     table->update_const_key_parts(conds);

sql/sql_select.cc

@@ -564,6 +564,7 @@ void JOIN::init(THD *thd_arg, List<Item> &fields_arg,
   is_orig_degenerated= false;
   with_ties_order_count= 0;
   prepared= false;
+  sql_cmd_dml= NULL;
 };
 
 

sql/sql_select.h

@@ -33,6 +33,7 @@
 #include "records.h"                          /* READ_RECORD */
 #include "opt_range.h"                /* SQL_SELECT, QUICK_SELECT_I */
 #include "filesort.h"
+#include "sql_delete.h"
 
 #include "cset_narrowing.h"
 
@@ -1722,6 +1723,13 @@ class JOIN :public Sql_alloc
   */
   bool is_orig_degenerated;
 
+  /*
+    UPDATE and DELETE may have an imitation JOIN, which is not NULL,
+    but has NULL join_tab. In such cases we may want to access
+    sql_cmd_dml::scanned_rows to choose optimization strategies.
+  */
+  Sql_cmd_dml *sql_cmd_dml;
+
   JOIN(THD *thd_arg, List<Item> &fields_arg, ulonglong select_options_arg,
        select_result *result_arg)
     :fields_list(fields_arg)

sql/sql_update.cc

@@ -423,7 +423,7 @@ bool Sql_cmd_update::update_single_table(THD *thd)
   switch_to_nullable_trigger_fields(*values, table);
 
   /* Apply the IN=>EXISTS transformation to all subqueries and optimize them */
-  if (select_lex->optimize_unflattened_subqueries(false))
+  if (select_lex->optimize_unflattened_subqueries(true))
     DBUG_RETURN(TRUE);
 
   if (conds)
@@ -481,6 +481,8 @@ bool Sql_cmd_update::update_single_table(THD *thd)
       goto produce_explain_and_leave;
 
     delete select;
+    if (select_lex->optimize_unflattened_subqueries(false))
+      DBUG_RETURN(TRUE);
     free_underlaid_joins(thd, select_lex);
     /*
       There was an error or the error was already sent by
@@ -533,8 +535,18 @@ bool Sql_cmd_update::update_single_table(THD *thd)
 
   table->update_const_key_parts(conds);
   order= simple_remove_const(order, conds);
-  query_plan.scanned_rows= select? select->records: table->file->stats.records;
-        
+
+  /*
+    Estimate the number of scanned rows and have it accessible in
+    JOIN::choose_subquery_plan() from the outer join through
+    JOIN::sql_cmd_dml
+  */
+  scanned_rows= query_plan.scanned_rows= select ?
+    select->records : table->file->stats.records;
+  select_lex->join->sql_cmd_dml= (Sql_cmd_dml *) this;
+  if (select_lex->optimize_unflattened_subqueries(false))
+    DBUG_RETURN(TRUE);
+
   if (select && select->quick && select->quick->unique_key_range())
   {
     /* Single row select (always "ordered"): Ok to use with key field UPDATE */