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Re: Implementing SQL/PSM for PG 8.2 - debugger

From: "Jonah H(dot) Harris" <jharris(at)tvi(dot)edu>
To: Dave Cramer <pg(at)fastcrypt(dot)com>
Cc: Pavel Stehule <stehule(at)kix(dot)fsv(dot)cvut(dot)cz>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Neil Conway <neilc(at)samurai(dot)com>,Jan Wieck <JanWieck(at)Yahoo(dot)com>,Denis Lussier <denis(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Implementing SQL/PSM for PG 8.2 - debugger
Date: 2005-06-28 21:58:52
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers

I lean with you and Tom.  While running it over the same libpq protocol 
would be helpful in some ways, it would have a lot of drawbacks and 
would really change the function of libpq.  I think a separate debugging 
protocol is in order.

Also, as far as bytecode comments go, let's separate them from this 
thread.  I have a pretty sweet hand-written stack-based VM that 
understands PL/SQL, but it's kinda old and written using PCCTS 1.33 (a 
recursive descent parser).  It has compilation, decompilation, and full 
debugging capabilities.  Unfortunately, PCCTS is no longer maintained as 
Terrence Parr (the originator) has since moved to ANTLR.  ANTLR 
currently does not generate C code although I have done some starting 
work on it (ANTLR currently generates Python, Java, or C++).  I don't 
suggest we really reuse one of the current VMs as it would require a lot 
more support and coordination.  Let's take the bytecode discussion off 
this thread and move it to another.  There is certainly a good and bad 
side to using bytecode and I would be glad to discuss it in another thread.

Dave Cramer wrote:

> Pavel,
> I am in agreement with Tom here, we should use a separate port, and  
> protocol specifically designed for this.
> My understanding is that this protocol would be synchronous, and be  
> used for transferring state information, variables, etc back and forth
> whereas the existing protocol would still be used to transfer data  
> back and forth
> Dave
> On 28-Jun-05, at 10:36 AM, Pavel Stehule wrote:
>> On Tue, 28 Jun 2005, Tom Lane wrote:
>>> Pavel Stehule <stehule(at)kix(dot)fsv(dot)cvut(dot)cz> writes:
>>>>> What do you think you need for enhanced protocol ?
>>>> What I need? Some like synchronous elog(NOTICE,''), which can  
>>>> return some
>>>> user's interaction, if it's possible. I didn't find how I do it with
>>>> current set of messages. But my knowleadges of protocol are minimal.
>>> It'd probably be smarter to manage the debugging across a separate
>>> connection, so that you could carry out debugging without requiring
>>> sophisticated support for it inside the client program.  If it's
>>> single-connection then it will be essentially impractical to debug
>>> except from a few specialized clients such as pgadmin; which will
>>> make it hard to investigate behaviors that are only seen under load
>>> from a client app.
>> I don't think it. Debug process halt query process in bouth variants -
>> remote | protocol. Remote debugging has one advance. I can monitor any
>> living plpgsql process, but I have to connect to some special port,  
>> and it
>> can be problem. Protocol debugging can be supported libpq, and all  
>> clients
>> libpq can debug. But is problem if PostgreSQL support bouth variants?
>> btw: debuging have to be only for some users,
>>     GRANT DEBUG ON LANGUAGE plpgsql TO ..
>> For me, is better variant if I can debug plpgsql code in psql console.
>> Without spec application. I don't speak so spec application don't  
>> have to
>> exists (from my view, ofcourse).
>> Maybe:
>>     set debug_mode to true; -- if 't' then func stmt has src
>>     reset function myfce(integer, integer); -- need recompilation
>>     create breakpoint on myfce(integer, integer) line 1;
>>     select myfce(10,10);
>>     dbg> \l .. list current line
>>          \c .. continue
>>          \n .. next stmt
>>              \L .. show src
>>          \s .. show stack
>>          \b .. switch breakpoint
>>              \q .. quit function
>>              select myvar+10 .. any sql expression
>>          variable .. print variable
>>         \c
>>     myfce
>>         -----
>>          10
>> that's all. Maybe I have big fantasy :).
>> Regards
>> Pavel
>> + small argument: if psql support debug mode, I don't need leave my  
>> emacs
>> postgresql mode.
>>> I don't know exactly how to cause such a connection to get set up,
>>> especially remotely.  But we should try to think of a way.
>>>             regards, tom lane
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