[SailfishDevel] SQLite linking

[Slava Monich]

On 06/03/17 10:49, Martin Kampas wrote:
> Hi Rinigus,
>
> Did you consider this recommendation?
>
> "To simplify matters, SQLite is also available as a pre-packaged 
> amalgamation source code file: sqlite3.c. The amalgamation is a single 
> file of ANSI-C code that implements the entire SQLite library. The 
> amalgamation is much easier to deal with. Everything is contained 
> within a single code file, so it is easy to drop into the source tree 
> of a larger C or C++ program. [...] /For these reasons, the 
> amalgamation source file ("sqlite3.c") is recommended for all 
> applications/."[1]
>
> What are the reasons that prevent you from using the upstream 
> recommended approach? Are they worth your time and effort?
>

I was always amused by this recommendation. Note that they carefully say 
"it is easy to drop into the source tree of a LARGER C or C++ program". 
Even they do understand that it's ridiculous to drop 200k lines of 
obscure code into a poor little program that just happened to be in need 
of some database access.

But yeah, if you have written a few million lines of code, adding 200k 
more is not such a big deal. Still, I would personally prefer to use the 
system library for the sake of performance, future updates, bug fixes 
and system-specific tweaks.

Here's a good example - by default sqlite3.c is using up to 2MB+500KB of 
memory for some sort of cache, meaning that every app that has some use 
of sqlite would consume at least 2.5MB of heap. That code will never 
deallocate anything until the buffer fills up, it's that bad. It was 
quite noticeable on the heap usage graph. We have reduced that to 
500KB+125KB and things got better:

https://git.merproject.org/mer-core/sqlite/commit/f132f16b

However, it obviously doesn't affect the apps which have that default 
2.5MB limit compiled in. Those will happily continue eating up memory.

I would encourage the developers to use the system sqlite library.

Cheers,
-Slava
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