Hello Alexander,
Thank for these news.
1) without pragma, lots of
sql_lex.h(732): error C4099: 'LEX': type name first seen using 'struct' now
seen using 'class'
2) Transform select : I' m new on Mariadb, but doing this kind of
transformation on other sgbd that I know (oracle, sqlserver, Sybase, db2) is a
performance killer ('or' operator is always complex for optimizer and to use
indexes).
For our application (who has more than 21000 stored procedures), some functions
needs attention :
a) substr (return null instead '' and if pos=0 act like if pos=1. On Mariadb,
if pos=0 , result is '')
MariaDB [(none)]> select substr('abcd',0,3);
+--------------------+
| substr('abcd',0,3) |
+--------------------+
| |
+--------------------+
Oracle:
SQL> select substr('abcd',0,3) from dual;
SUB
---
abc
b) ltrim and rtrim : return null instead ''
c) instr : return null instead 1 if searched string is ''
d) length : return null instead 0 if searched string is ''
4) Sorry, I didn't find operator || in documentation.
But there is a problem : on Oracle, concat string with null does not return
null.
MariaDB [(none)]> select 'a'||null||'b';
+----------------+
| 'a'||null||'b' |
+----------------+
| NULL |
+----------------+
Oracle:
SQL> select 'a'||null||'b' from dual;
'A
--
ab
Do you have any idea when the "GOTO" instruction will be implemented?
Best regards,
Jérôme.
-----Message d'origine-----
De : Alexander Barkov [mailto:b...@mariadb.org]
Envoyé : mardi 20 décembre 2016 03:40
À : jerome brauge; MariaDB Developers
Objet : Re: MDEV-10142 - bb-10.2-compatibility
Hello Jerome,
On 12/19/2016 05:16 PM, jerome brauge wrote:
> Hello,
> To build this branch on windows (Visual Studio Express 2015), I have to add
> "#pragma warning( disable : 4099 )" in sql_lex.h.
> But I don't know if it's the right solution.
What happened without #pragma?
>
> I have some questions:
> - I read the comment of Michael Widenius on subtask MDEV-10574.
> I think that it's important to change behavior of string functions whose
> returns a string (like rtrim, ltrim, substring, concat, ...) to return null
> instead of ''.
> Without this, we have to use UDF instead native functions and it's never
> good from a performance point of view.
> Have you made a decision ?
The current plan is to do these transformations:
1. Transform Insert
- insert values ("") -> insert values (null)
2. Transform Select
- where v=x => (v <> "" and V=X)
- where v is null => (v="" or v is null)
We didn't plan to change functions yet. Thanks for bringing this up.
We'll discuss this.
>
> - On Oracle, we can easily disable/enable triggers. I found an old request
> for this on jira : MDEV-7579. As you already manage order_action now, perhaps
> you can simply use negative orders to indicate disabled triggers.
Thanks. We'll also discuss this.
I'll let you know a few days later.
>
> - do you have planning to implement operator || to concat strings ?
This feature is available since early MySQL versions, just to make sure to set
sql_mode:
> MariaDB [test]> SET sql_mode=ORACLE;
> Query OK, 0 rows affected (0.00 sec)
>
> MariaDB [test]> SELECT 'a'||'b';
> +----------+
> | 'a'||'b' |
> +----------+
> | ab |
> +----------+
> 1 row in set (0.00 sec)
>
> Best regards,
> J. Brauge
>
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