bzr push into mysql-5.5-next-mr branch (alik:2935 to 2937)

[Alexander Nozdrin]

 2937 Alexander Nozdrin	2009-11-06 [merge]
      Auto-merge from mysql-trunk-merge.

    modified:
      libmysql/libmysql.c
      mysql-test/t/disabled.def
 2936 Alexander Nozdrin	2009-11-06 [merge]
      Manual merge from mysql-trunk-merge.

    modified:
      mysql-test/r/innodb_lock_wait_timeout_1.result
      mysql-test/t/innodb_lock_wait_timeout_1.test
      sql/item_subselect.cc
      sql/records.cc
      sql/records.h
      sql/sql_select.cc
      sql/sql_select.h
 2935 Alexander Nozdrin	2009-11-06 [merge]
      Auto-merge from mysql-trunk-merge.

    modified:
      extra/yassl/taocrypt/src/random.cpp
      mysql-test/lib/My/SafeProcess/safe_process_win.cc
=== modified file 'libmysql/libmysql.c'
--- a/libmysql/libmysql.c	2009-11-06 14:20:27 +0000
+++ b/libmysql/libmysql.c	2009-11-06 16:15:09 +0000
@@ -1260,12 +1260,14 @@ mysql_real_escape_string(MYSQL *mysql, c
 
 
 char * STDCALL
-mysql_odbc_escape_string(MYSQL *mysql,
-			 char *to, ulong to_length,
-			 const char *from, ulong from_length,
-			 void *param,
-			 char * (*extend_buffer)
-			 (void *, char *, ulong *))
+mysql_odbc_escape_string(MYSQL *mysql __attribute__((unused)),
+                         char *to __attribute__((unused)),
+                         ulong to_length __attribute__((unused)),
+                         const char *from __attribute__((unused)),
+                         ulong from_length __attribute__((unused)),
+                         void *param __attribute__((unused)),
+                         char * (*extend_buffer)(void *, char *, ulong *)
+                         __attribute__((unused)))
 {
   return NULL;
 }

=== modified file 'mysql-test/r/innodb_lock_wait_timeout_1.result'
--- a/mysql-test/r/innodb_lock_wait_timeout_1.result	2009-10-28 14:49:56 +0000
+++ b/mysql-test/r/innodb_lock_wait_timeout_1.result	2009-11-03 17:45:52 +0000
@@ -48,5 +48,310 @@ commit;
 set autocommit=default;
 drop table t1;
 #
+# Bug#41756 Strange error messages about locks from InnoDB
+#
+drop table if exists t1;
+# In the default transaction isolation mode, and/or with
+# innodb_locks_unsafe_for_binlog=OFF, handler::unlock_row()
+# in InnoDB does nothing.
+# Thus in order to reproduce the condition that led to the
+# warning, one needs to relax isolation by either
+# setting a weaker tx_isolation value, or by turning on
+# the unsafe replication switch.
+# For testing purposes, choose to tweak the isolation level,
+# since it's settable at runtime, unlike
+# innodb_locks_unsafe_for_binlog, which is
+# only a command-line switch.
+#
+set @@session.tx_isolation="read-committed";
+# Prepare data. We need a table with a unique index,
+# for join_read_key to be used. The other column
+# allows to control what passes WHERE clause filter.
+create table t1 (a int primary key, b int) engine=innodb;
+# Let's make sure t1 has sufficient amount of rows
+# to exclude JT_ALL access method when reading it,
+# i.e. make sure that JT_EQ_REF(a) is always preferred.
+insert into t1 values (1,1), (2,null), (3,1), (4,1),
+(5,1), (6,1), (7,1), (8,1), (9,1), (10,1),
+(11,1), (12,1), (13,1), (14,1), (15,1),
+(16,1), (17,1), (18,1), (19,1), (20,1);
+#
+# Demonstrate that for the SELECT statement
+# used later in the test JT_EQ_REF access method is used.
+#
+explain
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+select 2 as a, 2 as b) as t2 for update;
+id	1
+select_type	PRIMARY
+table	<derived2>
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	2
+Extra	
+id	1
+select_type	PRIMARY
+table	t1
+type	eq_ref
+possible_keys	PRIMARY
+key	PRIMARY
+key_len	4
+ref	t2.a
+rows	1
+Extra	Using where
+id	2
+select_type	DERIVED
+table	NULL
+type	NULL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	No tables used
+id	3
+select_type	UNION
+table	NULL
+type	NULL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	No tables used
+id	NULL
+select_type	UNION RESULT
+table	<union2,3>
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	
+#
+# Demonstrate that the reported SELECT statement
+# no longer produces warnings.
+#
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+select 2 as a, 2 as b) as t2 for update;
+1
+commit;
+# 
+# Demonstrate that due to lack of inter-sweep "reset" function,
+# we keep some non-matching records locked, even though we know
+# we could unlock them.
+# To do that, show that if there is only one distinct value
+# for a in t2 (a=2), we will keep record (2,null) in t1 locked.
+# But if we add another value for "a" to t2, say 6,
+# join_read_key cache will be pruned at least once, 
+# and thus record (2, null) in t1 will get unlocked.
+#
+begin;
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+select 2 as a, 2 as b) as t2 for update;
+1
+#
+# Switching to connection con1
+# We should be able to delete all records from t1 except (2, null),
+# since they were not locked.
+begin;
+# Delete in series of 3 records so that full scan
+# is not used and we're not blocked on record (2,null)
+delete from t1 where a in (1,3,4);
+delete from t1 where a in (5,6,7);
+delete from t1 where a in (8,9,10);
+delete from t1 where a in (11,12,13);
+delete from t1 where a in (14,15,16);
+delete from t1 where a in (17,18);
+delete from t1 where a in (19,20);
+# 
+# Record (2, null) is locked. This is actually unnecessary, 
+# because the previous select returned no rows. 
+# Just demonstrate the effect.
+#
+delete from t1;
+ERROR HY000: Lock wait timeout exceeded; try restarting transaction
+rollback;
+#
+# Switching to connection default
+#
+# Show that the original contents of t1 is intact:
+select * from t1;
+a	b
+1	1
+2	NULL
+3	1
+4	1
+5	1
+6	1
+7	1
+8	1
+9	1
+10	1
+11	1
+12	1
+13	1
+14	1
+15	1
+16	1
+17	1
+18	1
+19	1
+20	1
+commit;
+#
+# Have a one more record in t2 to show that 
+# if join_read_key cache is purned, the current
+# row under the cursor is unlocked (provided, this row didn't 
+# match the partial WHERE clause, of course).
+# Sic: the result of this test dependent on the order of retrieval
+# of records --echo # from the derived table, if !
+# We use DELETE to disable the JOIN CACHE. This DELETE modifies no
+# records. It also should leave no InnoDB row locks.
+#
+begin;
+delete t1.* from t1 natural join (select 2 as a, 2 as b union all
+select 0 as a, 0 as b) as t2;
+# Demonstrate that nothing was deleted form t1
+select * from t1;
+a	b
+1	1
+2	NULL
+3	1
+4	1
+5	1
+6	1
+7	1
+8	1
+9	1
+10	1
+11	1
+12	1
+13	1
+14	1
+15	1
+16	1
+17	1
+18	1
+19	1
+20	1
+#
+# Switching to connection con1
+begin;
+# Since there is another distinct record in the derived table
+# the previous matching record in t1 -- (2,null) -- was unlocked.
+delete from t1;
+# We will need the contents of the table again.
+rollback;
+select * from t1;
+a	b
+1	1
+2	NULL
+3	1
+4	1
+5	1
+6	1
+7	1
+8	1
+9	1
+10	1
+11	1
+12	1
+13	1
+14	1
+15	1
+16	1
+17	1
+18	1
+19	1
+20	1
+commit;
+#
+# Switching to connection default
+rollback;
+begin;
+#
+# Before this patch, we could wrongly unlock a record
+# that was cached and later used in a join. Demonstrate that
+# this is no longer the case.
+# Sic: this test is also order-dependent (i.e. the
+# the bug would show up only if the first record in the union
+# is retreived and processed first.
+#
+# Verify that JT_EQ_REF is used.
+explain
+select 1 from t1 natural join (select 3 as a, 2 as b union all
+select 3 as a, 1 as b) as t2 for update;
+id	1
+select_type	PRIMARY
+table	<derived2>
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	2
+Extra	
+id	1
+select_type	PRIMARY
+table	t1
+type	eq_ref
+possible_keys	PRIMARY
+key	PRIMARY
+key_len	4
+ref	t2.a
+rows	1
+Extra	Using where
+id	2
+select_type	DERIVED
+table	NULL
+type	NULL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	No tables used
+id	3
+select_type	UNION
+table	NULL
+type	NULL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	No tables used
+id	NULL
+select_type	UNION RESULT
+table	<union2,3>
+type	ALL
+possible_keys	NULL
+key	NULL
+key_len	NULL
+ref	NULL
+rows	NULL
+Extra	
+# Lock the record.
+select 1 from t1 natural join (select 3 as a, 2 as b union all
+select 3 as a, 1 as b) as t2 for update;
+1
+1
+# Switching to connection con1
+#
+# We should not be able to delete record (3,1) from t1,
+# (previously it was possible).
+#
+delete from t1 where a=3;
+ERROR HY000: Lock wait timeout exceeded; try restarting transaction
+# Switching to connection default
+commit;
+set @@session.tx_isolation=default;
+drop table t1;
+#
 # End of 5.1 tests
 #

=== modified file 'mysql-test/t/disabled.def'
--- a/mysql-test/t/disabled.def	2009-11-06 15:19:24 +0000
+++ b/mysql-test/t/disabled.def	2009-11-06 16:15:09 +0000
@@ -13,3 +13,5 @@ kill                     : Bug#37780 200
 query_cache_28249        : Bug#43861 2009-03-25 main.query_cache_28249 fails sporadically
 partition_innodb_builtin : Bug#32430 2009-09-25 mattiasj Waiting for push of Innodb
changes
 partition_innodb_plugin  : Bug#32430 2009-09-25 mattiasj Waiting for push of Innodb
changes
+innodb-autoinc           : Bug#48482 2009-11-02 svoj innodb-autoinc.test fails with
results difference
+rpl_killed_ddl           : Bug#45520: rpl_killed_ddl fails sporadically in pb2

=== modified file 'mysql-test/t/innodb_lock_wait_timeout_1.test'
--- a/mysql-test/t/innodb_lock_wait_timeout_1.test	2009-10-28 14:49:56 +0000
+++ b/mysql-test/t/innodb_lock_wait_timeout_1.test	2009-11-03 17:45:52 +0000
@@ -71,5 +71,160 @@ set autocommit=default;
 drop table t1;
 
 --echo #
+--echo # Bug#41756 Strange error messages about locks from InnoDB
+--echo #
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+--echo # In the default transaction isolation mode, and/or with
+--echo # innodb_locks_unsafe_for_binlog=OFF, handler::unlock_row()
+--echo # in InnoDB does nothing.
+--echo # Thus in order to reproduce the condition that led to the
+--echo # warning, one needs to relax isolation by either
+--echo # setting a weaker tx_isolation value, or by turning on
+--echo # the unsafe replication switch.
+--echo # For testing purposes, choose to tweak the isolation level,
+--echo # since it's settable at runtime, unlike
+--echo # innodb_locks_unsafe_for_binlog, which is
+--echo # only a command-line switch.
+--echo #
+set @@session.tx_isolation="read-committed";
+
+--echo # Prepare data. We need a table with a unique index,
+--echo # for join_read_key to be used. The other column
+--echo # allows to control what passes WHERE clause filter.
+create table t1 (a int primary key, b int) engine=innodb;
+--echo # Let's make sure t1 has sufficient amount of rows
+--echo # to exclude JT_ALL access method when reading it,
+--echo # i.e. make sure that JT_EQ_REF(a) is always preferred.
+insert into t1 values (1,1), (2,null), (3,1), (4,1),
+                      (5,1), (6,1), (7,1), (8,1), (9,1), (10,1),
+                      (11,1), (12,1), (13,1), (14,1), (15,1),
+                      (16,1), (17,1), (18,1), (19,1), (20,1);
+--echo #
+--echo # Demonstrate that for the SELECT statement
+--echo # used later in the test JT_EQ_REF access method is used.
+--echo #
+--vertical_results
+explain
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+                               select 2 as a, 2 as b) as t2 for update;
+--horizontal_results
+--echo #
+--echo # Demonstrate that the reported SELECT statement
+--echo # no longer produces warnings.
+--echo #
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+                               select 2 as a, 2 as b) as t2 for update;
+commit;
+--echo # 
+--echo # Demonstrate that due to lack of inter-sweep "reset" function,
+--echo # we keep some non-matching records locked, even though we know
+--echo # we could unlock them.
+--echo # To do that, show that if there is only one distinct value
+--echo # for a in t2 (a=2), we will keep record (2,null) in t1 locked.
+--echo # But if we add another value for "a" to t2, say 6,
+--echo # join_read_key cache will be pruned at least once, 
+--echo # and thus record (2, null) in t1 will get unlocked.
+--echo #
+begin;
+select 1 from t1 natural join (select 2 as a, 1 as b union all
+                               select 2 as a, 2 as b) as t2 for update;
+connect (con1,localhost,root,,);
+--echo #
+--echo # Switching to connection con1
+connection con1;
+--echo # We should be able to delete all records from t1 except (2, null),
+--echo # since they were not locked.
+begin;
+--echo # Delete in series of 3 records so that full scan
+--echo # is not used and we're not blocked on record (2,null)
+delete from t1 where a in (1,3,4);
+delete from t1 where a in (5,6,7);
+delete from t1 where a in (8,9,10);
+delete from t1 where a in (11,12,13);
+delete from t1 where a in (14,15,16);
+delete from t1 where a in (17,18);
+delete from t1 where a in (19,20);
+--echo # 
+--echo # Record (2, null) is locked. This is actually unnecessary, 
+--echo # because the previous select returned no rows. 
+--echo # Just demonstrate the effect.
+--echo #
+--error ER_LOCK_WAIT_TIMEOUT
+delete from t1;
+rollback;
+--echo #
+--echo # Switching to connection default
+connection default;
+--echo #
+--echo # Show that the original contents of t1 is intact:
+select * from t1;
+commit;
+--echo #
+--echo # Have a one more record in t2 to show that 
+--echo # if join_read_key cache is purned, the current
+--echo # row under the cursor is unlocked (provided, this row didn't 
+--echo # match the partial WHERE clause, of course).
+--echo # Sic: the result of this test dependent on the order of retrieval
+--echo # of records --echo # from the derived table, if !
+--echo # We use DELETE to disable the JOIN CACHE. This DELETE modifies no
+--echo # records. It also should leave no InnoDB row locks.
+--echo #
+begin;
+delete t1.* from t1 natural join (select 2 as a, 2 as b union all
+                                  select 0 as a, 0 as b) as t2;
+--echo # Demonstrate that nothing was deleted form t1
+select * from t1;
+--echo #
+--echo # Switching to connection con1
+connection con1;
+begin;
+--echo # Since there is another distinct record in the derived table
+--echo # the previous matching record in t1 -- (2,null) -- was unlocked.
+delete from t1;
+--echo # We will need the contents of the table again.
+rollback;
+select * from t1;
+commit;
+--echo #
+--echo # Switching to connection default
+connection default;
+rollback;
+begin;
+--echo #
+--echo # Before this patch, we could wrongly unlock a record
+--echo # that was cached and later used in a join. Demonstrate that
+--echo # this is no longer the case.
+--echo # Sic: this test is also order-dependent (i.e. the
+--echo # the bug would show up only if the first record in the union
+--echo # is retreived and processed first.
+--echo #
+--echo # Verify that JT_EQ_REF is used.
+--vertical_results
+explain
+select 1 from t1 natural join (select 3 as a, 2 as b union all
+                               select 3 as a, 1 as b) as t2 for update;
+--horizontal_results
+--echo # Lock the record.
+select 1 from t1 natural join (select 3 as a, 2 as b union all
+                               select 3 as a, 1 as b) as t2 for update;
+--echo # Switching to connection con1
+connection con1;
+--echo #
+--echo # We should not be able to delete record (3,1) from t1,
+--echo # (previously it was possible).
+--echo #
+--error ER_LOCK_WAIT_TIMEOUT
+delete from t1 where a=3;
+--echo # Switching to connection default
+connection default;
+commit;
+
+disconnect con1;
+set @@session.tx_isolation=default;
+drop table t1;
+
+--echo #
 --echo # End of 5.1 tests
 --echo #

=== modified file 'sql/item_subselect.cc'
--- a/sql/item_subselect.cc	2009-11-06 14:20:27 +0000
+++ b/sql/item_subselect.cc	2009-11-06 16:13:33 +0000
@@ -1956,6 +1956,7 @@ int subselect_single_select_engine::exec
               tab->read_record.record= tab->table->record[0];
               tab->read_record.thd= join->thd;
               tab->read_record.ref_length= tab->table->file->ref_length;
+              tab->read_record.unlock_row= rr_unlock_row;
               *(last_changed_tab++)= tab;
               break;
             }

=== modified file 'sql/records.cc'
--- a/sql/records.cc	2009-11-06 14:20:27 +0000
+++ b/sql/records.cc	2009-11-06 16:13:33 +0000
@@ -67,6 +67,7 @@ void init_read_record_idx(READ_RECORD *i
   info->file=  table->file;
   info->record= table->record[0];
   info->print_error= print_error;
+  info->unlock_row= rr_unlock_row;
 
   table->status=0;			/* And it's always found */
   if (!table->file->inited)
@@ -192,6 +193,7 @@ void init_read_record(READ_RECORD *info,
   }
   info->select=select;
   info->print_error=print_error;
+  info->unlock_row= rr_unlock_row;
   info->ignore_not_found_rows= 0;
   table->status=0;			/* And it's always found */
 

=== modified file 'sql/records.h'
--- a/sql/records.h	2009-10-16 15:58:26 +0000
+++ b/sql/records.h	2009-11-06 16:13:33 +0000
@@ -43,11 +43,13 @@ class SQL_SELECT;
 struct READ_RECORD
 {
   typedef int (*Read_func)(READ_RECORD*);
+  typedef void (*Unlock_row_func)(st_join_table *);
   typedef int (*Setup_func)(struct st_join_table*);
 
   TABLE *table;                                 /* Head-form */
   handler *file;
   TABLE **forms;                                /* head and ref forms */
+  Unlock_row_func unlock_row;
   Read_func read_record;
   THD *thd;
   SQL_SELECT *select;
@@ -72,4 +74,6 @@ void init_read_record_idx(READ_RECORD *i
                           bool print_error, uint idx);
 void end_read_record(READ_RECORD *info);
 
+void rr_unlock_row(st_join_table *tab);
+
 #endif /* SQL_RECORDS_H */

=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2009-11-06 15:28:25 +0000
+++ b/sql/sql_select.cc	2009-11-06 16:15:09 +0000
@@ -150,6 +150,7 @@ static int join_read_const_table(JOIN_TA
 static int join_read_system(JOIN_TAB *tab);
 static int join_read_const(JOIN_TAB *tab);
 static int join_read_key(JOIN_TAB *tab);
+static void join_read_key_unlock_row(st_join_table *tab);
 static int join_read_always_key(JOIN_TAB *tab);
 static int join_read_last_key(JOIN_TAB *tab);
 static int join_no_more_records(READ_RECORD *info);
@@ -5736,7 +5737,9 @@ static bool create_ref_for_key(JOIN *joi
   }
   j->ref.key_buff2=j->ref.key_buff+ALIGN_SIZE(length);
   j->ref.key_err=1;
+  j->ref.has_record= FALSE;
   j->ref.null_rejecting= 0;
+  j->ref.use_count= 0;
   keyuse=org_keyuse;
 
   store_key **ref_key= j->ref.key_copy;
@@ -6569,6 +6572,20 @@ make_join_select(JOIN *join,SQL_SELECT *
   DBUG_RETURN(0);
 }
 
+
+/**
+  The default implementation of unlock-row method of READ_RECORD,
+  used in all access methods.
+*/
+
+void rr_unlock_row(st_join_table *tab)
+{
+  READ_RECORD *info= &tab->read_record;
+  info->file->unlock_row();
+}
+
+
+
 static void
 make_join_readinfo(JOIN *join, ulonglong options)
 {
@@ -6584,6 +6601,7 @@ make_join_readinfo(JOIN *join, ulonglong
     TABLE *table=tab->table;
     tab->read_record.table= table;
     tab->read_record.file=table->file;
+    tab->read_record.unlock_row= rr_unlock_row;
     tab->next_select=sub_select;		/* normal select */
 
     /*
@@ -6629,6 +6647,7 @@ make_join_readinfo(JOIN *join, ulonglong
       delete tab->quick;
       tab->quick=0;
       tab->read_first_record= join_read_key;
+      tab->read_record.unlock_row= join_read_key_unlock_row;
       tab->read_record.read_record= join_no_more_records;
       if (table->covering_keys.is_set(tab->ref.key) &&
 	  !table->no_keyread)
@@ -11472,7 +11491,7 @@ evaluate_join_record(JOIN *join, JOIN_TA
     else
     {
       join->thd->warning_info->inc_current_row_for_warning();
-      join_tab->read_record.file->unlock_row();
+      join_tab->read_record.unlock_row(join_tab);
     }
   }
   else
@@ -11483,7 +11502,7 @@ evaluate_join_record(JOIN *join, JOIN_TA
     */
     join->examined_rows++;
     join->thd->warning_info->inc_current_row_for_warning();
-    join_tab->read_record.file->unlock_row();
+    join_tab->read_record.unlock_row(join_tab);
   }
   return NESTED_LOOP_OK;
 }
@@ -11843,18 +11862,55 @@ join_read_key(JOIN_TAB *tab)
       table->status=STATUS_NOT_FOUND;
       return -1;
     }
+    /*
+      Moving away from the current record. Unlock the row
+      in the handler if it did not match the partial WHERE.
+    */
+    if (tab->ref.has_record && tab->ref.use_count == 0)
+    {
+      tab->read_record.file->unlock_row();
+      tab->ref.has_record= FALSE;
+    }
     error=table->file->index_read_map(table->record[0],
                                       tab->ref.key_buff,
                                       make_prev_keypart_map(tab->ref.key_parts),
                                       HA_READ_KEY_EXACT);
     if (error && error != HA_ERR_KEY_NOT_FOUND && error !=
HA_ERR_END_OF_FILE)
       return report_error(table, error);
+
+    if (! error)
+    {
+      tab->ref.has_record= TRUE;
+      tab->ref.use_count= 1;
+    }
+  }
+  else if (table->status == 0)
+  {
+    DBUG_ASSERT(tab->ref.has_record);
+    tab->ref.use_count++;
   }
   table->null_row=0;
   return table->status ? -1 : 0;
 }
 
 
+/**
+  Since join_read_key may buffer a record, do not unlock
+  it if it was not used in this invocation of join_read_key().
+  Only count locks, thus remembering if the record was left unused,
+  and unlock already when pruning the current value of
+  TABLE_REF buffer.
+  @sa join_read_key()
+*/
+
+static void
+join_read_key_unlock_row(st_join_table *tab)
+{
+  DBUG_ASSERT(tab->ref.use_count);
+  if (tab->ref.use_count)
+    tab->ref.use_count--;
+}
+
 /*
   ref access method implementation: "read_first" function
 

=== modified file 'sql/sql_select.h'
--- a/sql/sql_select.h	2009-11-06 14:20:27 +0000
+++ b/sql/sql_select.h	2009-11-06 16:13:33 +0000
@@ -61,6 +61,8 @@ class store_key;
 typedef struct st_table_ref
 {
   bool		key_err;
+  /** True if something was read into buffer in join_read_key.  */
+  bool          has_record;
   uint          key_parts;                ///< num of ...
   uint          key_length;               ///< length of key_buff
   int           key;                      ///< key no
@@ -88,6 +90,11 @@ typedef struct st_table_ref
   table_map	depend_map;		  ///< Table depends on these tables.
   /* null byte position in the key_buf. Used for REF_OR_NULL optimization */
   uchar          *null_ref_key;
+  /*
+    The number of times the record associated with this key was used
+    in the join.
+  */
+  ha_rows       use_count;
 } TABLE_REF;
 
 


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