Fix for bug #11896 "Partial locking in case of recursive trigger definitions".

If we are in stored function or trigger we should ensure that we won't change
table that is already used by calling statement (this can damage table or
easily cause infinite loops). Particularly this means that recursive triggers
should be disallowed.

mysql-test/r/sp-error.result

@@ -299,6 +299,36 @@ lock tables t1 read, mysql.proc read|
 unlock tables|
 lock tables mysql.proc write|
 unlock tables|
+drop function if exists f1|
+create function f1(i int) returns int
+begin
+insert into t1 (val) values (i);
+return 0;
+end|
+select val, f1(val) from t1|
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select val, f1(val) from t1 as tab|
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select * from t1|
+val	x
+42	3.1
+19	1.2
+update t1 set val= f1(val)|
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select * from t1|
+val	x
+42	3.1
+19	1.2
+select f1(17)|
+f1(17)
+0
+select * from t1|
+val	x
+42	3.1
+19	1.2
+17	NULL
+delete from t1 where val= 17|
+drop function f1|
 create procedure bug1965()
 begin
 declare c cursor for select val from t1 order by valname;

mysql-test/r/trigger.result

@@ -664,3 +664,44 @@ end|
 update t1 set data = 1;
 update t1 set data = 2;
 drop table t1;
+create table t1 (f1 integer);
+create table t2 (f2 integer);
+create trigger t1_ai after insert on t1
+for each row insert into t2 values (new.f1+1);
+create trigger t2_ai after insert on t2
+for each row insert into t1 values (new.f2+1);
+insert into t1 values (1);
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select * from t1;
+f1
+1
+select * from t2;
+f2
+2
+drop trigger t1_ai;
+drop trigger t2_ai;
+create trigger t1_bu before update on t1
+for each row insert into t1 values (2);
+update t1 set f1= 10;
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select * from t1;
+f1
+1
+drop trigger t1_bu;
+create trigger t1_bu before update on t1
+for each row delete from t1 where f1=new.f1;
+update t1 set f1= 10;
+ERROR HY000: Can't update table 't1' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
+select * from t1;
+f1
+1
+drop trigger t1_bu;
+create trigger t1_bi before insert on t1
+for each row set new.f1=(select sum(f1) from t1);
+insert into t1 values (3);
+select * from t1;
+f1
+1
+1
+drop trigger t1_bi;
+drop tables t1, t2;

mysql-test/t/sp-error.test

@@ -409,6 +409,35 @@ lock tables mysql.proc write|
 unlock tables|
 
 
+#
+# Check that in functions we don't allow to update tables which
+# are used by statements which invoke these functions.
+#
+--disable_warnings
+drop function if exists f1|
+--enable_warnings
+create function f1(i int) returns int
+begin
+  insert into t1 (val) values (i);
+  return 0;
+end|
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+select val, f1(val) from t1|
+# Table alias should not matter
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+select val, f1(val) from t1 as tab|
+select * from t1|
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+update t1 set val= f1(val)|
+select * from t1|
+# But this should be OK
+select f1(17)|
+select * from t1|
+# Cleanup
+delete from t1 where val= 17|
+drop function f1|
+
+
 #
 # BUG#1965
 #

mysql-test/t/trigger.test

@@ -685,3 +685,39 @@ update t1 set data = 2;
 
 connection default;
 drop table t1;
+
+# Test for bug #11896 "Partial locking in case of recursive trigger
+# definitions". Recursion in triggers should not be allowed.
+# We also should not allow to change tables which are used in
+# statements invoking this trigger.
+create table t1 (f1 integer);
+create table t2 (f2 integer);
+create trigger t1_ai after insert on t1
+  for each row insert into t2 values (new.f1+1);
+create trigger t2_ai after insert on t2
+  for each row insert into t1 values (new.f2+1);
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+insert into t1 values (1);
+select * from t1;
+select * from t2;
+drop trigger t1_ai;
+drop trigger t2_ai;
+create trigger t1_bu before update on t1
+  for each row insert into t1 values (2);
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+update t1 set f1= 10;
+select * from t1;
+drop trigger t1_bu;
+create trigger t1_bu before update on t1
+  for each row delete from t1 where f1=new.f1;
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+update t1 set f1= 10;
+select * from t1;
+drop trigger t1_bu;
+# This should work tough
+create trigger t1_bi before insert on t1
+  for each row set new.f1=(select sum(f1) from t1);
+insert into t1 values (3);
+select * from t1;
+drop trigger t1_bi;
+drop tables t1, t2;

sql/share/errmsg.txt

@@ -5395,3 +5395,5 @@ ER_TOO_BIG_DISPLAYWIDTH 42000 S1009
 	eng "Display width out of range for column '%-.64s' (max = %d)"
 ER_XAER_DUPID XAE08
         eng "XAER_DUPID: The XID already exists"
+ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+        eng "Can't update table '%-.64s' in stored function/trigger because it is already used by statement which invoked this stored function/trigger."

sql/sql_base.cc

@@ -1046,11 +1046,28 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   {						// Using table locks
     TABLE *best_table= 0;
     int best_distance= INT_MIN;
+    bool check_if_used= thd->prelocked_mode &&
+                        ((int) table_list->lock_type >=
+                         (int) TL_WRITE_ALLOW_WRITE);
     for (table=thd->open_tables; table ; table=table->next)
     {
       if (table->s->key_length == key_length &&
-          !memcmp(table->s->table_cache_key, key, key_length) &&
-          !my_strcasecmp(system_charset_info, table->alias, alias) &&
+          !memcmp(table->s->table_cache_key, key, key_length))
+      {
+        if (check_if_used && table->query_id &&
+            table->query_id != thd->query_id)
+        {
+          /*
+            If we are in stored function or trigger we should ensure that
+            we won't change table that is already used by calling statement.
+            So if we are opening table for writing, we should check that it
+            is not already open by some calling stamement.
+          */
+          my_error(ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG, MYF(0),
+                   table->s->table_name);
+          DBUG_RETURN(0);
+        }
+        if (!my_strcasecmp(system_charset_info, table->alias, alias) &&
             table->query_id != thd->query_id && /* skip tables already used */
             !(thd->prelocked_mode && table->query_id))
         {
@@ -1061,8 +1078,8 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
             or has the best suitable lock. In case there is no locked
             table that has an equal or higher lock than requested,
             we us the closest matching lock to be able to produce an error
-          message about wrong lock mode on the table. The best_table is changed
-          if bd < 0 <= d or bd < d < 0 or 0 <= d < bd.
+            message about wrong lock mode on the table. The best_table
+            is changed if bd < 0 <= d or bd < d < 0 or 0 <= d < bd.
 
             distance <  0 - No suitable lock found
             distance >  0 - we have lock mode higher then we require
@@ -1073,11 +1090,20 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
           {
             best_distance= distance;
             best_table= table;
-          if (best_distance == 0)               // Found perfect lock
+            if (best_distance == 0 && !check_if_used)
+            {
+              /*
+                If we have found perfect match and we don't need to check that
+                table is not used by one of calling statements (assuming that
+                we are inside of function or trigger) we can finish iterating
+                through open tables list.
+              */
               break;
             }
           }
         }
+      }
+    }
     if (best_table)
     {
       table= best_table;