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Because MariaDB does not accept a constant virtual column (other DBMS's do) I was obliged to write the noconst UDF as:
/***********************************************************************/ /* Returns its argument saying it is not a constant. */ /***********************************************************************/ my_bool noconst_init(UDF_INIT *initid, UDF_ARGS *args, char *message) { if (args->arg_count != 1 || args->arg_type[0] != STRING_RESULT) { strcpy(message, "noconst unique argument must be a string"); return true; } // endif arg initid->const_item = false; // The trick! return false; } // end of noconst_init char *noconst(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *res_length, char *, char *) { return args->args[0]; } // end of noconst
Now, creating the table t1, inserting one line to it and displaying it does work:
MariaDB [test]> create table t1 (
-> n int key not null auto_increment,
-> msg char(20) as (noconst('Hello World')) virtual);
Query OK, 0 rows affected (0.06 sec)
MariaDB [test]> insert into t1() values();
Query OK, 1 row affected (0.01 sec)
MariaDB [test]> select * from t1;
+---+-------------+
| n | msg |
+---+-------------+
| 1 | Hello World |
+---+-------------+
1 row in set (0.00 sec)
However, later on when stopping the server a crash occurs in the function:
void udf_handler::cleanup()
{
if (!not_original)
{
if (initialized)
{
if (u_d->func_deinit != NULL)
{
Udf_func_deinit deinit= u_d->func_deinit;
(*deinit)(&initid);
}
free_udf(u_d);
initialized= FALSE;
}
if (buffers) // Because of bug in ecc
delete [] buffers;
buffers= 0;
}
}
See the attach udf_crash.log.
The same kind of crash occurs with different other UDF's.
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Done.
Stack trace from 5.5 commit 29ac245dd04c5416d57a90b0ab3c4d08cbc4d723
#3 <signal handler called> #4 0x00000000008500ae in udf_handler::cleanup (this=0x7f11c2875968) at 5.5/sql/item_func.cc:3454 #5 0x00000000008514e0 in Item_udf_func::cleanup (this=0x7f11c28758a0) at 5.5/sql/item_func.cc:3766 #6 0x00000000006073a1 in Item::delete_self (this=0x7f11c28758a0) at 5.5/sql/item.h:1434 #7 0x000000000060162f in Query_arena::free_items (this=0x7f11c2874bf8) at 5.5/sql/sql_class.cc:3164 #8 0x00000000006fcf32 in closefrm (table=0x7f11c2828e60, free_share=true) at 5.5/sql/table.cc:2773 #9 0x00000000005d4378 in intern_close_table (table=0x7f11c2828e60) at 5.5/sql/sql_base.cc:929 #10 0x00000000005d43e5 in free_cache_entry (table=0x7f11c2828e60) at 5.5/sql/sql_base.cc:952 #11 0x00000000005d4763 in close_cached_tables (thd=0x0, tables=0x0, wait_for_refresh=false, timeout=31536000) at 5.5/sql/sql_base.cc:1059 #12 0x00000000005d3111 in table_def_start_shutdown () at 5.5/sql/sql_base.cc:410 #13 0x0000000000586faf in clean_up (print_message=true) at 5.5/sql/mysqld.cc:1822 #14 0x0000000000586d9e in unireg_end () at 5.5/sql/mysqld.cc:1735 #15 0x0000000000586cc0 in kill_server (sig_ptr=0x0) at 5.5/sql/mysqld.cc:1663 #16 0x0000000000586cdd in kill_server_thread (arg=0x7f11ed3b9e98) at 5.5/sql/mysqld.cc:1686 #17 0x00007f11ecfaab50 in start_thread (arg=<optimized out>) at pthread_create.c:304 #18 0x00007f11eb26095d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
That's a surprise it works at all, documentation says UDFs are not allowed for virtual columns.
Olivier Bertrand,
Could you please attach the whole c file with your UDF function? It will be faster than me creating missing parts.