Re: [Ruby-DBI-devel] methods disappearing in ruby-mysql-2.4.2a

[Michael N. <uu...@rz...>]

On Mon, May 13, 2002 at 11:35:54AM -0700, Brad Hilton wrote:
> On Sun, 2002-05-12 at 21:20, Sean Chittenden wrote:
> > > Right now the could looks like:
> > > 
> > > @res_handle.free if @res_handle
> > > 
> > > Perhaps that needs to be changed to:
> > > 
> > > @res_handle.free if (@res_handle and @res_handle.is_a? MysqlRes)
> > > 
> > > I don't know...
> > 
> > I'm a PostgreSQL guy myself.  Could you test the above change and see
> > if it works for you?  You seem to have done the diagnosis correctly
> > and I think it should work.  -sc
> 
> Actually, I think a better solution than my previous one is to set
> query_with_result = true in Mysql.rb line 313 in execute().  It is
> obvious that the code expects query_with_result to be set to true in
> that instance, and there are many places in the code that assume
> @res_handle is a MysqlRes object, so I believe this would be the best
> solution.
> 
> Attached is a sample script which exposes the problem, as well as a
> patch to fix the bug.

This will not completely fix the bug, I fear. 

When executing statements concurrently, it could happen that method #do
sets query_with_result=false, then #execute interrupts and sets 
query_with_result=true ....

The solution is to use a Mutex, which prevents parallel execution of 
methods #do and #execute.

The following patch fixes it (checked into -current):

----- patch ------


5c5
< # Version : 0.3.1
---
> # Version : 0.3.2
24a25
> require "thread"   # for Mutex
30c31
< VERSION          = "0.3.1"
---
> VERSION          = "0.3.2"
148a150,154
>   def initialize(handle, attr)
>     super
>     @mutex = Mutex.new 
>   end
> 
208d213
< 
210d214
<     @handle.query_with_result = false
212,213c216,220
<     @handle.query(sql)
<     @handle.affected_rows
---
>     @mutex.synchronize { 
>       @handle.query_with_result = false
>       @handle.query(sql)
>       @handle.affected_rows     # return value
>     }
220c227
<     Statement.new(self, @handle, statement)
---
>     Statement.new(self, @handle, statement, @mutex)
297c304
<   def initialize(parent, handle, statement)
---
>   def initialize(parent, handle, statement, mutex)
300c307
<     @parent, @handle = parent, handle
---
>     @parent, @handle, @mutex = parent, handle, mutex
303d309
<     @handle.query_with_result = true # automatically switches store_result on 
313,315c319,325
<     @res_handle = @handle.query(@prep_stmt.bind(@params))
<     @current_row = 0
<     @rows = @handle.affected_rows
---
>     sql = @prep_stmt.bind(@params)
>     @mutex.synchronize {
>       @handle.query_with_result = true
>       @res_handle = @handle.query(sql)
>       @current_row = 0
>       @rows = @handle.affected_rows
>     }








-- 
Michael Neumann  ***  eMail uu...@rz...