Re: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
Personally I would start from the database and generate code to match the schema. Like others pointed out it's fairly difficult to go the other way.
RE: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
Hello John-
Thanks for your comments. Could you please provide some details on how
you have generated XML from custom data-structure and how you propose to
do this for SQL schema as well.
Any code examples would really help.
Rajan
>-Original Message-
>From: John Stanton [mailto:[EMAIL PROTECTED]
>Sent: Monday, October 17, 2005 7:40 AM
>To: sqlite-users@sqlite.org
>Subject: Re: [sqlite] Question about automatic schema creation from
custom
>data-strucutre for persistence storage
>
>I addressed this some time back in a C program which dynamically
>generates XML. Generating SQL would be an option.
>
>By building a table with a keyname for each data element and a pointer
>to a data item the output structure can be assembled. As a wise person
>once told me "There is no problem in CS which cannot be solved by yet
>another level of indirection".
>
>In my case I also added a function pointer so that callbacks could be
>used. With XML the table is actually a transformation of the DTD so
>that the result is guaranteed to be "well formed". If the table were
>compiled from the data structure then a similar integrity could be
assured.
>
>This method would require a few lines of code, but you would only need
>to do it once as opposed to writing code for each data structure.
>JS
>
>Dan Kennedy wrote:
>> As far as I know C++ has no introspection capability so the answer
>> is probably no. Unless you want to parse your header file yourself,
>> or something like that.
>>
>> With Java or another high-level programming language that supports
>> introspection it would be possible I think.
>>
>>
>> "Rajan, Vivek K" <[EMAIL PROTECTED]> wrote:
>> Hello-
>>
>>
>>
>> Has anyone had experience with automatically creating schema from a
>> custom data-structure for persistence storage using SQLite? So, in my
>> C/C++ program I have the following type of data-structure:
>>
>>
>>
>> struct _trace {
>>
>> std::string name;
>>
>> std::string prop;
>>
>> std:string object;
>>
>> int a;
>>
>> double b;
>>
>> };
>>
>>
>>
>> std::vector _myPath;
>>
>>
>> Now, let's say I want to write and read _myPath data-structure
>> (persistence) in SQLite database.
>>
>>
>>
>> My questions:
>>
>> - Is there a mechanism to dynamically create a schema on-the-fly from
>> the data-structure?
>>
>> - Essentially a capability to store any custom data-structure into
>> SQLite data-base by automatic creation of schema for the
data-structure
>>
>>
>>
>> Rajan
>>
>>
>>
>>
>>
>>
>>
>> -
>> Yahoo! Music Unlimited - Access over 1 million songs. Try it free.
RE: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
I my experience, the best approach is to create a description of your data
in a form that is good for being parsed and feeding into a code generator.
C structures are not good for this, they are good for being compiled into
executable code.
I would create a data description, and use it to generate the SQL and the C
structures. The data description could be whatever you find convenient: I
use XML, but anything will do so long as it is expressive enough for you and
you can parse it.
I use a code generation tool called Cog (http://nedbatchelder.com/code/cog)
to generate the code itself.
--Ned.
http://nedbatchelder.com
-Original Message-
From: John Stanton [mailto:[EMAIL PROTECTED]
Sent: Monday, 17 October, 2005 10:40 AM
To: sqlite-users@sqlite.org
Subject: Re: [sqlite] Question about automatic schema creation from custom
data-strucutre for persistence storage
I addressed this some time back in a C program which dynamically
generates XML. Generating SQL would be an option.
By building a table with a keyname for each data element and a pointer
to a data item the output structure can be assembled. As a wise person
once told me "There is no problem in CS which cannot be solved by yet
another level of indirection".
In my case I also added a function pointer so that callbacks could be
used. With XML the table is actually a transformation of the DTD so
that the result is guaranteed to be "well formed". If the table were
compiled from the data structure then a similar integrity could be assured.
This method would require a few lines of code, but you would only need
to do it once as opposed to writing code for each data structure.
JS
Dan Kennedy wrote:
> As far as I know C++ has no introspection capability so the answer
> is probably no. Unless you want to parse your header file yourself,
> or something like that.
>
> With Java or another high-level programming language that supports
> introspection it would be possible I think.
>
>
> "Rajan, Vivek K" <[EMAIL PROTECTED]> wrote:
> Hello-
>
>
>
> Has anyone had experience with automatically creating schema from a
> custom data-structure for persistence storage using SQLite? So, in my
> C/C++ program I have the following type of data-structure:
>
>
>
> struct _trace {
>
> std::string name;
>
> std::string prop;
>
> std:string object;
>
> int a;
>
> double b;
>
> };
>
>
>
> std::vector _myPath;
>
>
> Now, let's say I want to write and read _myPath data-structure
> (persistence) in SQLite database.
>
>
>
> My questions:
>
> - Is there a mechanism to dynamically create a schema on-the-fly from
> the data-structure?
>
> - Essentially a capability to store any custom data-structure into
> SQLite data-base by automatic creation of schema for the data-structure
>
>
>
> Rajan
>
>
>
>
>
>
>
> -
> Yahoo! Music Unlimited - Access over 1 million songs. Try it free.
Re: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
I addressed this some time back in a C program which dynamically
generates XML. Generating SQL would be an option.
By building a table with a keyname for each data element and a pointer
to a data item the output structure can be assembled. As a wise person
once told me "There is no problem in CS which cannot be solved by yet
another level of indirection".
In my case I also added a function pointer so that callbacks could be
used. With XML the table is actually a transformation of the DTD so
that the result is guaranteed to be "well formed". If the table were
compiled from the data structure then a similar integrity could be assured.
This method would require a few lines of code, but you would only need
to do it once as opposed to writing code for each data structure.
JS
Dan Kennedy wrote:
As far as I know C++ has no introspection capability so the answer
is probably no. Unless you want to parse your header file yourself,
or something like that.
With Java or another high-level programming language that supports
introspection it would be possible I think.
"Rajan, Vivek K" <[EMAIL PROTECTED]> wrote:
Hello-
Has anyone had experience with automatically creating schema from a
custom data-structure for persistence storage using SQLite? So, in my
C/C++ program I have the following type of data-structure:
struct _trace {
std::string name;
std::string prop;
std:string object;
int a;
double b;
};
std::vector _myPath;
Now, let's say I want to write and read _myPath data-structure
(persistence) in SQLite database.
My questions:
- Is there a mechanism to dynamically create a schema on-the-fly from
the data-structure?
- Essentially a capability to store any custom data-structure into
SQLite data-base by automatic creation of schema for the data-structure
Rajan
-
Yahoo! Music Unlimited - Access over 1 million songs. Try it free.
Re: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
.Net has a tool (xsd.exe) that can convert C# structure to XML schema.
I don't know whether it can help you.
- Original Message -
From: "Dan Kennedy" <[EMAIL PROTECTED]>
To: <sqlite-users@sqlite.org>
Sent: Monday, October 17, 2005 4:50 PM
Subject: Re: [sqlite] Question about automatic schema creation from custom
data-strucutre for persistence storage
> As far as I know C++ has no introspection capability so the answer
> is probably no. Unless you want to parse your header file yourself,
> or something like that.
>
> With Java or another high-level programming language that supports
> introspection it would be possible I think.
>
>
> "Rajan, Vivek K" <[EMAIL PROTECTED]> wrote:
> Hello-
>
>
>
> Has anyone had experience with automatically creating schema from a
> custom data-structure for persistence storage using SQLite? So, in my
> C/C++ program I have the following type of data-structure:
>
>
>
> struct _trace {
>
> std::string name;
>
> std::string prop;
>
> std:string object;
>
> int a;
>
> double b;
>
> };
>
>
>
> std::vector _myPath;
>
>
> Now, let's say I want to write and read _myPath data-structure
> (persistence) in SQLite database.
>
>
>
> My questions:
>
> - Is there a mechanism to dynamically create a schema on-the-fly from
> the data-structure?
>
> - Essentially a capability to store any custom data-structure into
> SQLite data-base by automatic creation of schema for the data-structure
>
>
>
> Rajan
>
>
>
>
>
>
>
> -
> Yahoo! Music Unlimited - Access over 1 million songs. Try it free.
Re: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
As far as I know C++ has no introspection capability so the answer
is probably no. Unless you want to parse your header file yourself,
or something like that.
With Java or another high-level programming language that supports
introspection it would be possible I think.
"Rajan, Vivek K" <[EMAIL PROTECTED]> wrote:
Hello-
Has anyone had experience with automatically creating schema from a
custom data-structure for persistence storage using SQLite? So, in my
C/C++ program I have the following type of data-structure:
struct _trace {
std::string name;
std::string prop;
std:string object;
int a;
double b;
};
std::vector _myPath;
Now, let's say I want to write and read _myPath data-structure
(persistence) in SQLite database.
My questions:
- Is there a mechanism to dynamically create a schema on-the-fly from
the data-structure?
- Essentially a capability to store any custom data-structure into
SQLite data-base by automatic creation of schema for the data-structure
Rajan
-
Yahoo! Music Unlimited - Access over 1 million songs. Try it free.
Re: [sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
Rajan, Vivek K wrote: > - Is there a mechanism to dynamically create a schema on-the-fly from >the data-structure? > > - Essentially a capability to store any custom data-structure into >SQLite data-base by automatic creation of schema for the data-structure > > I don't know about creating a schema from a data structure, but I have some experience going in the other direction, including automatic generation of SQL queries. I'm using this on a very large point of sale system at the moment (although sadly neither with SQLite or C). In going from schema to code the most important thing is that you need a certain degree of consistency in your code. For each table that you want to generate objects for, it's highly recommended that you have a single unique primary key, and that key is system-assigned. This lends itself well to Boyce-Codd normal form, where the computer and the user have a different idea of what the primary key is, and the user's key has a uniqueness constraint upon it. I understand that this doesn't fly well with some DBAs. I'm not a sophisticated enough designer to understand their objections, but the design works well enough for my purposes. Clay Dowling
[sqlite] Question about automatic schema creation from custom data-strucutre for persistence storage
Hello-
Has anyone had experience with automatically creating schema from a
custom data-structure for persistence storage using SQLite? So, in my
C/C++ program I have the following type of data-structure:
struct _trace {
std::string name;
std::string prop;
std:stringobject;
int a;
doubleb;
};
std::vector _myPath;
Now, let's say I want to write and read _myPath data-structure
(persistence) in SQLite database.
My questions:
- Is there a mechanism to dynamically create a schema on-the-fly from
the data-structure?
- Essentially a capability to store any custom data-structure into
SQLite data-base by automatic creation of schema for the data-structure
Rajan
