mysql-native: preview2

[Suliman via Digitalmars-d-announce]

On Thursday, 2 February 2017 at 14:08:19 UTC, Steven 
Schveighoffer wrote:
> On 2/2/17 1:50 AM, Suliman wrote:
>> On Thursday, 2 February 2017 at 05:28:10 UTC, Nick Sabalausky 
>> wrote:
>>> Made a couple more long-needed changes while I'm at it:
>>>
>>> https://github.com/Abscissa/mysql-native-experimental
>>> Tag: v0.2.0-preview2
>>>
>>> - For better clarity, renamed `mysql.db.MysqlDB` to
>>> `mysql.pool.MySqlPool`.
>>>
>>> - Package mysql.connection no longer acts as a package.d, 
>>> publicly
>>> importing other modules. To import all of mysql-native, use 
>>> `import
>>> mysql;`
>>
>> Thanks! Could you explain about pool. I googled about it, and 
>> still
>> can't understand when it up new connections?
>>
>> How can I imagine what connection is? Because without it hard 
>> to
>> understand what difference between connections with and 
>> without pool.
>>
>> Am I right understand that if I use pool I can create 
>> connection
>> instance one time in DB class constructor end every new 
>> connection will
>> be created on demand?
>
> Just to answer some of this, because I had questions about the 
> pool as well.
>
> The ConnectionPool is a mechanism to allow a limited resource 
> (or a resource you want to limit, depending how you look at it) 
> to be pooled for use. It's basically a free-list. It also 
> abstracts away the details of opening a connection (i.e. server 
> ip, username, password). It's nice because it makes opening a 
> connection cleaner and straightforward.
>
> The resulting connection can only be used in one fiber at a 
> time, and the connection pool itself can only be used in one 
> thread ever (there is no sharing of connection pools between 
> threads). The resulting connection struct is reference counted, 
> so it automatically releases back to the pool when it goes out 
> of scope.
>
> One issue I had with MysqlDB (now MySqlPool) is that it doesn't 
> allow you to actually put a limit on the connections. In other 
> words, you can't say "only allow 50 simultaneous connections". 
> The effect is that you save the connection initialization, but 
> you can't put a hard cap on connections used in your thread. If 
> you have 10,000 fibers running at once, then you may get 10,000 
> connections to the database that are left open. If each of 
> those is a socket, you are consuming a lot of resources during 
> down times.
>
> Not to mention that the allocation of the 10,000th connection 
> has to first go on a linear search through the 9,999 other 
> connections to find an open one (this seems like it could be 
> solved better with a linked-list freelist?).
>
> See here: https://github.com/mysql-d/mysql-native/issues/74
>
> BTW, I solved this by copying MysqlDB into my local project and 
> adding the appropriate parameter to the constructor :)
>
> -Steve

Do you mean that every new fiber open new connection? And when 
fiber is yield it's return connection to the pool?

Could you explain real case if rangification of ResultSet

http://semitwist.com/mysql-native-docs/v0.2.0-preview1/mysql/result/ResultSet.html

Does it's mean that I can write
foreach(x;result.empty) ? Or how to use it?