Re: Question to Lua and Postgres (and ConTeXt)

[Hans Hagen <pragma@wxs.nl>]

On 12/20/2017 8:12 PM, Tomas Hala wrote:
> Hi all,
> 
> I installed the module (I'm at CentOS 6.6) by yum install luasql-postgres, ok. Then I used:
> 
> lua	myscript.lua
> /usr/bin/lua	myscript.lua
> /usr/local/bin/lua myscript.lua
> 
> I discovered that it is version dependent: lua (=/usr/local/bin/lua) does not operate, it is 5.3, whereas /usr/bin/lua works ok, it is 5.1.
> At the command line, it is not a problem to choose another lua interpreter than the default one is.
> But if I use the same lua script within the ConTeXt, I came across the same problem because the default version in ConTeXt is 5.2.
> 
> First, I thought about the way how to change version of lua inside the current version of ConTeXt  (is it possible?)
> but the same behaviour appeared when I tryed older versions (TL 2010, 2011, 2012) containing lua v5.1 by the default.
> It seems that file postgres.so which is the main important is not visible for ConTeXt.
> 
> Neither
> 	 package.path = '/usr/lib/lua/5.1/luasql;',
> not copying the postgres.so to the current directory did not help.
> 
> I have any clue how to fix it. Have you any ideas?

I never used postgres (it's on my todo list to have a look at it, as we 
also ship mysql and sqlite support in context where we don't depend on 
libraries).

The current Luatex is 5.2 so you can forget about 5.1 then. Beginnning 
next year we will switch the garden version of luatex to use lua 5.3 but 
for tex live we will wait till after the 2018 code freeze (we might 
provide an extra luatex53 for testing so that one can take a year to 
update). We might provide a compile switch for 5.2 after we move 
forward. The context code is already 5.3 ready (that is: for as far as 
we can see and have tested) and i run luatex with 5.3 .. so, you can:

(1) wait till we move the 53 related code into experimental (this might 
happen around the turn of the year
(2) decide to delay 5.3 till we release a beta based on experimental
(3) find some 52 suitable code (and keep in mind then that we will move 
to 53)

For those who are curious about why we don't simply switch: there is a 
fundamental low level change in lua (number system) that in some usage 
can have consequences. Our (luigi and i) experiences are:

(1) one has to adapt code, but it's often clear when; one also have to 
realize that luajittex is a hybrid 5.1/5.2 and some day maybe 5.3

(2) we have done quite some testing to figure out a dramatic 
(showstopping) slowdown in number to string conversion but in the end 
managed to get around it

(3) we measure some 5-10 overal speed improvement on average context 
usage (upto some 10% on lua runs but we spend only 50% time in lua, so 
th egap between luatex and luajittex becomes smaller) as tex has a lot 
of integer manipulations

In retrospect on the one hand it was easier than we thought but we spent 
quite some time on it anyway (and of course we then wonder if it's worth 
the time and trouble as it never pays off).

> Thanks in advance,
> 
> Tomáš
> 
> %%%%%%%%
> 
> ! LuaTeX error <main ctx instance>:3: module 'luasql.postgres' not found:
> 	no field package.preload['luasql.postgres']
> 	no file './luasql/postgres.so'
> 	no file '/usr/local/lib/lua/5.1/luasql/postgres.so'
> 	no file '/usr/local/lib/lua/5.1/loadall.so'
> 	no file './luasql.so'
> 	no file '/usr/local/lib/lua/5.1/luasql.so'
> 	no file '/usr/local/lib/lua/5.1/loadall.so'
> stack traceback:
> 	[C]: in function 'require'
> 	<main ctx instance>:3: in main chunk.
> 
> %%%%%%%%
> 
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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