On 8/23/15, Abilio Marques <abiliojr at gmail.com> wrote:
>
> 1. sqlite3 CLI doesn't seem to "load" the .so easily... The generated so is
> called "lua.ext". If I run "*.load lua.ext*" it claims that there is no .so
> available. I went into renaming the file to lua.so, and ran *.load lua.so*
> ... Got: *Error: Shared object "lua.so.so <http://lua.so.so>" not found,
> required by "sqlite3"* ... then tried with *.load lua* ... I guessed that
> would work... but got *Error: Shared object "lua.so" not found, required by
> "sqlite3*", even when the file was present at that directory... But then I
> ran *.load ./lua.so* , and even *.load ./lua* ... both loaded without
> problems... Is that the correct behavior?
Yes. You each have to specify a pathname or else the library must be
on LD_LIBRARY_PATH. I think this is a security restriction. Maybe
somebody else can shed more light on the matter.
>
> 2. Which is the convention for the file extension of a loadable module? .so
> and .dll?, or is there any other name used regularly among sqlite3 users?
.so for linux. .dylib for mac. .dll for windows.
You can just do ".load ./lua" without the suffix and SQLite will
supply the correct suffix for your platform.
>
> 3. Lua can return arrays. Also, Lua can return multiple values. Tried to
> take advantage of those facts, but while reading the SQLite API
> documentation, found no function where I could map multiple values as the
> return of a function. Am I wrong? For example:
>
> select * from table t where fieldA in (lua('return 1,2,3'));
>
> Could be a useful feat in real scripts with real code.
>
Regular SQL functions always return scalars in SQLite.
See https://www.sqlite.org/src/artifact/b8fb7befd85b3a9b for an
example of how to implement table-valued functions. This is a new
feature so there is no documentation on it yet. But the example is
well-commented. This capability will be in the next release, so
you'll have to compile from trunk if you want to use it right away -
it is not found in 3.8.11.1.
--
D. Richard Hipp
drh at sqlite.org
