What is recommended way to initialize and keep prepared statements in go Lang

[shrin...@gmail.com]

Hi Team ,

I am new in go lang ,I want to know is there any recommended way in go lang to create prepare statement in go lang on application start and pass it to multiple http handler so that query can be done inside those http handlers.

[Marcin Romaszewicz]

Do you mean a SQL prepared statement?

Check out the database/sql package. The database connection abstraction has a Prepare function which creates a statement. Keep in mind, that based on your level of concurrency, the statement will be re-prepared in each new connection that's opened up on your behalf. So, what you need to do is keep a persistent instance of sql.DB, which will try to maintain your prepared statements for you.

On Sat, Apr 13, 2019 at 10:58 AM <shrin...@gmail.com> wrote:

Hi Team ,

I am new in go lang ,I want to know is there any recommended way in go lang to create prepare statement in go lang on application start and pass it to multiple http handler so that query can be done inside those http handlers.

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[Shrinath agarwal]

Hi Marcin,

I know about Prepare function supported by sql package .My initial question was what is better way to pass multiple prepare statements on different http handlers .

ex: we can construct struct like this 

type Database struct {

    db *sql.DB

    someStmt *sql.Stmt

    // etc.

}

but since we have multiple prepare statements this struct will keep on increasing so my question was is there any better way provided in golang like in java (where we can initialize prepare statement in class constructor and use that )

--

Thanks and Regards,

 

Shri Nath Agarwal

Mobile 9482060723

[Marcin Romaszewicz]

In Go, you can simply create a CreateDatabase() function which initializes your prepared statements, in lieu of the constructor.

When doing a SQL query, you must use the correct prepared statement for it, so whether you have an array of them, or each is its own field, each handler would have to use the correct Statement. Is this different in Java somehow, does it automatically use the correct prepared statement or something?

-- Marcin

[er...@tibco.com]

On Sunday, April 14, 2019 at 3:17:46 AM UTC-7, Shrinath agarwal wrote:

Hi Marcin,

I know about Prepare function supported by sql package .My initial question was what is better way to pass multiple prepare statements on different http handlers .

ex: we can construct struct like this 

type Database struct {

    db *sql.DB

    someStmt *sql.Stmt

    // etc.

}

but since we have multiple prepare statements this struct will keep on increasing so my question was is there any better way provided in golang like in java (where we can initialize prepare statement in class constructor and use that )

On the one hand, this seems like a neat approach, having all the prepared statements in a struct. On the other hand, the compiler isn't really giving you any extra help, unless you do more work. By which I mean, instead of using a generic statement, create methods with the exact set of parameters, and wrap the call to execute the underlying prepared statement. That way, the compiler helps ensure that all the parameters to the statement are correct.

That might be an interesting approach. If the application won't benefit from that, however, this also seems like it might be optimizing the design for the wrong characteristics. The approach described prevents lazy loading - instead requiring preparing all statements when the application starts the connection...

As best I understand it, the better database drivers will cache all the prepared statements for you already. Which means it is safe to call Prepare() in the function where you need it. If the database has seen the Prepare() call before, and hasn't dropped it from its cache, it will simply use an already prepared version of the statement. Also, there's a distinction between calling Prepare() on the database, vs. calling Prepare() on a transaction. The result of Prepare() on the transaction is valid for the scope of the transaction, and shouldn't be called after the end of the transaction. Also, I suspect that Prepare() statements are not the bottleneck of the application, but whether or not they are, test before assuming!

Just to illustrate my point about different design characteristics, alternate approaches:

• A struct that has a "Prepare()" method that takes a label for what is to be prepared, rather than a statement. That way, if statements are already prepared, the Prepare() method can just look them up.
• Create an interface for the existing use of the DB object, and implement caching of Prepare() results yourself. (Do a performance check first, to see if this even matters!)

Difficult to tell which is the right approach, without further understanding of the requirements.

Eric.

 

On Sun, Apr 14, 2019 at 7:59 AM Marcin Romaszewicz <mar...@gmail.com> wrote:

Do you mean a SQL prepared statement?

Check out the database/sql package. The database connection abstraction has a Prepare function which creates a statement. Keep in mind, that based on your level of concurrency, the statement will be re-prepared in each new connection that's opened up on your behalf. So, what you need to do is keep a persistent instance of sql.DB, which will try to maintain your prepared statements for you.

On Sat, Apr 13, 2019 at 10:58 AM <shrin...@gmail.com> wrote:

Hi Team ,

I am new in go lang ,I want to know is there any recommended way in go lang to create prepare statement in go lang on application start and pass it to multiple http handler so that query can be done inside those http handlers.

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[Ross Light]

(+cc golang-nuts, +bcc go-cloud)

go-cloud is for the discussion of the Go CDK. This sounds like a more general Go question, so redirecting you over to golang-nuts.

-Ross

On Mon, Apr 15, 2019 at 12:52 PM Shrinath agarwal <shrin...@gmail.com> wrote:

Hi Team ,I am new in Go lang .I am trying to learn now-days ,I want to know is there any recommended way to initialize prepared statements and keep passing them in multiple http handler so that it can get used in those handlers .

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[roger peppe]

The way I've been doing this recently is to write two methods for each statement, one to prepare it and one to use it.

That way the SQL code sits next to the Exec or Query statement that uses it, making it easier to understand what's going on.

Here's some example code showing the way we've been structuring this. It would normally be split across several files (I've left comments where I'd split it).

https://play.golang.org/p/fh9b7loZkLJ

It's a little tedious to do this, but eliminates a few common sources of errors, and ends up quite readable IMHO.

Hope this helps,

  rog.

On Sat, 13 Apr 2019 at 18:58, <shrin...@gmail.com> wrote:

Hi Team ,

I am new in go lang ,I want to know is there any recommended way in go lang to create prepare statement in go lang on application start and pass it to multiple http handler so that query can be done inside those http handlers.

--
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