Re: [HACKERS] How to refer to resource files from UDFs written in C

2017-06-09 Thread Supun Nakandala
On Fri, Jun 9, 2017 at 3:05 AM, Heikki Linnakangas  wrote:

> On 06/09/2017 08:56 AM, Supun Nakandala wrote:
>
>> Hi hackers,
>>
>> I am trying to extend PostgreSQL by adding UDT and UDF for a custom use
>> case and I am using C language extensions to do that.
>>
>> However, I have a requirement of reading a text file from one of the C
>> functions. The compiled *.so files are placed in the "pg_config
>> --pkglibdir" directory and tried copying my text files there but it didn't
>> work. I found that, when these shared libs are loaded they are run from a
>> different working directory. In this case, what is the best way to refer
>> to
>> my text files from the C code other than giving the absolute path which
>> can
>> change from system to system.
>>
>
> All backend processes run with the data directory as the current
> directory. So you can put the files into the data directory, probably best
> to have a subdirectory there to avoid confusing them with PostgreSQL's own
> files. Or you could have a config option, to set an absolute path.
>
> - Heikki
>
>
Thank you everyone for your quick replies. I ended up copying the files to
the data directory and referring using relative path.


Re: [HACKERS] How to refer to resource files from UDFs written in C

2017-06-09 Thread Tom Lane
Supun Nakandala  writes:
> However, I have a requirement of reading a text file from one of the C
> functions. The compiled *.so files are placed in the "pg_config
> --pkglibdir" directory and tried copying my text files there but it didn't
> work. I found that, when these shared libs are loaded they are run from a
> different working directory. In this case, what is the best way to refer to
> my text files from the C code other than giving the absolute path which can
> change from system to system.

You probably want to use get_share_path, or one of its sibling functions
in src/port/path.c.  Then your files go with the PG installation tree,
whereever it is.  There are different functions that are appropriate for
different types of files.

regards, tom lane


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Re: [HACKERS] How to refer to resource files from UDFs written in C

2017-06-09 Thread Heikki Linnakangas

On 06/09/2017 08:56 AM, Supun Nakandala wrote:

Hi hackers,

I am trying to extend PostgreSQL by adding UDT and UDF for a custom use
case and I am using C language extensions to do that.

However, I have a requirement of reading a text file from one of the C
functions. The compiled *.so files are placed in the "pg_config
--pkglibdir" directory and tried copying my text files there but it didn't
work. I found that, when these shared libs are loaded they are run from a
different working directory. In this case, what is the best way to refer to
my text files from the C code other than giving the absolute path which can
change from system to system.


All backend processes run with the data directory as the current 
directory. So you can put the files into the data directory, probably 
best to have a subdirectory there to avoid confusing them with 
PostgreSQL's own files. Or you could have a config option, to set an 
absolute path.


- Heikki



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[HACKERS] How to refer to resource files from UDFs written in C

2017-06-08 Thread Supun Nakandala
Hi hackers,

I am trying to extend PostgreSQL by adding UDT and UDF for a custom use
case and I am using C language extensions to do that.

However, I have a requirement of reading a text file from one of the C
functions. The compiled *.so files are placed in the "pg_config
--pkglibdir" directory and tried copying my text files there but it didn't
work. I found that, when these shared libs are loaded they are run from a
different working directory. In this case, what is the best way to refer to
my text files from the C code other than giving the absolute path which can
change from system to system.

Thank you.
Supun