On 3/8/18 6:57 AM, bauss wrote:
On Thursday, 8 March 2018 at 06:49:52 UTC, Nick Sabalausky (Abscissa)
wrote:
On 03/07/2018 02:32 PM, bauss wrote:
Wait why has it been updated to array() ? So it's not a real range
anymore? Or was it always represented as an array behind the scenes?
I just feel like allocating it into an additional array is a waste of
memory? But if it was always like that I guess it doesn't matter.
query() returns an input range. You can only access one element at a
time (as its read from the network) and you don't know how many there
are ahead of time, BUT it avoids allocating a whole array to store
everything.
In addition to query(), there used to also be a querySet(). The
querySet() would allocate an array and read ALL the results into it so
you could get random-access. But that's exactly what you already get
when you call array() on an input range (such as the input range
returned by query), so querySet was deemed redundant and eliminated.
So if you had code that *did* need an array allocated to store all the
results, then "querySet()" has been replaced with "query().array". But
like you said, if you don't really need the array, then there's no
need to call array() and waste the memory.
However idk what I changed, but the issue stopped for me.
However I still have this issue:
https://github.com/mysql-d/mysql-native/issues/153
(Currently trying to see if I can make a minimal example, but it's
kinda hard to make a minimal example since it's from my Diamond MVC
(vibe.d) library and it isn't used until deep nesting of the
application.
Anyway before I report anything else I could easily be doing
something wrong. There hasn't exactly been any good examples on how
to use it with vibe.d so it has pretty much been a trial and error
thing for me.
Using mysql-native with vibe.d isn't any different from using it
without vibe.d.
It's recommended to use MySQLPool to make a Connection rather than
doing "new Connection" directly simply because connecting is faster
that way (though "new Connection" will still work).
But aside from that, there is absolutely nothing different about
mysql-native whether you're using vibe.d or not.
So basically I keep an associative array of connection pools based on
connection strings like below:
private static __gshared MySQLPool[string] _pools;
And then I retrieve a connection with the function below.
Perhaps I'm not supposed to make a new pool every time, but there is
someway to retrieve a pool already? Maybe that's what I'm doing wrong?
private static shared globalPoolLock = new Object;
private Connection getMySqlConnection(string connectionString)
{
auto pool = _pools.get(connectionString, null);
if (!pool)
{
synchronized (globalPoolLock)
{
pool = new MySQLPool(connectionString);
_pools[connectionString] = pool;
}
}
return pool.lockConnection();
}
After I retrieve the connection then it's basically like the code I
showed you, but that seem to be correct, yes?
Does your application need to support multiple connection strings
while it's running? That's pretty rare unless you're making something
like phpMyAdmin (and even then, I'd probably do it a little
differently). Normally you'd just make one connection pool:
MySQLPool pool;
Then "new" that once with your connection string when you start up,
and you're good.
I guess I can imagine some potential use-cases that get more
complicated than that, but that's really up to your own project's needs.
> However I still have this issue:
>
> https://github.com/mysql-d/mysql-native/issues/153
>
> (Currently trying to see if I can make a minimal example, but
it's kinda
> hard to make a minimal example since it's from my Diamond MVC
(vibe.d)
> library and it isn't used until deep nesting of the
application.
I'm only guessing here, but I wonder if that might be because you seem
to be trying to share pools and connections across threads. I don't
know whether vibe is designed to share TCP connections across threads
or not. I'd say, try ripping out all that
shared/__gshared/synchronized stuff and see how that works.
But if you can't store the pools anywhere, how are you supposed to use
them with vibe.d?
Creating a new pool for every thread seems expensive and dosn't that
defeat the purpose of using pools in the first place?
I mean a 1000 people could connect to a website and potentially that
could create a thousand threads (It probably won't, BUT it could.) and
thus it can't be afforded to create a pool per request.
Well, vibe.d shouldn't be doing that. It creates fibers per request, not
threads, no?
I would expect no more than one thread per core to be created, and you
can afford that many pools (I'd create them at program/thread startup in
any case).
The point of a pool is to avoid some costly setup. In my case, I'm not
even closing the connection because I feel the "cost" of allocating a
connection from the heap isn't worth worrying about. But I also limit
the pool so it's only going to allow X concurrent Db connections per thread.
-Steve
