[HACKERS] converting datum to numeric
Hi, I've got a couple of questions. I was using numeric_out like this: DatumGetCString(DirectFunctionCall1(numeric_out, d)); Why do I have to use DirectFunctionCall1 instead of calling numeric_out? I was suggested to use numeric_send instead of numeric_out, however when changing the function names in the above example, the whole expression returns 8. Always 8. I check with: char *x = DatumGetCString(DirectFunctionCall1(numeric_send, d)); PLy_elog(NOTICE, x). And my main question: is there any documentation about those internal functions, which use and when etc? thanks Szymon
Re: [HACKERS] converting datum to numeric
Hello 2013/6/25 Szymon Guz mabew...@gmail.com: Hi, I've got a couple of questions. I was using numeric_out like this: DatumGetCString(DirectFunctionCall1(numeric_out, d)); Why do I have to use DirectFunctionCall1 instead of calling numeric_out? numeric_out functions doesn't use C calling convention - it use own convention for support NULL values and some other informations. DirectFunctionCall1 is simple function that transform C like call to PostgreSQL call. You can do it directly, but you have to prepare necessary structures. I was suggested to use numeric_send instead of numeric_out, however when changing the function names in the above example, the whole expression returns 8. Always 8. I check with: char *x = DatumGetCString(DirectFunctionCall1(numeric_send, d)); PLy_elog(NOTICE, x). send functions are used for binary protocol - so it is nonsense. And my main question: is there any documentation about those internal functions, which use and when etc? source code :( and http://www.postgresql.org/docs/9.2/static/xfunc-c.html src/backend/utils/atd/* is very useful and contains lot of materials for study some examples of usage you can find in contrib examples http://www.postgresql.org/docs/9.2/static/extend.html Regards Pavel thanks Szymon -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] converting datum to numeric
On 25 June 2013 08:51, Pavel Stehule pavel.steh...@gmail.com wrote: Hello 2013/6/25 Szymon Guz mabew...@gmail.com: Hi, I've got a couple of questions. I was using numeric_out like this: DatumGetCString(DirectFunctionCall1(numeric_out, d)); Why do I have to use DirectFunctionCall1 instead of calling numeric_out? numeric_out functions doesn't use C calling convention - it use own convention for support NULL values and some other informations. DirectFunctionCall1 is simple function that transform C like call to PostgreSQL call. You can do it directly, but you have to prepare necessary structures. I was suggested to use numeric_send instead of numeric_out, however when changing the function names in the above example, the whole expression returns 8. Always 8. I check with: char *x = DatumGetCString(DirectFunctionCall1(numeric_send, d)); PLy_elog(NOTICE, x). send functions are used for binary protocol - so it is nonsense. Hi, thanks for the information. So I will leave speeding it up for this moment. thanks, Szymon
