Обсуждение: [GENERAL] Executing regex in C code

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[GENERAL] Executing regex in C code

От
Gabriel Furstenheim Milerud
Дата:
Hi,
I'm trying to execute the equivalent to '~' with regexp from within C code. According to pg_operator this operator for type text corresponds to textregexeq:

  DATA(insert OID = 641 ( "~" PGNSP PGUID b f f 25 25 16 0 642 textregexeq regexeqsel regexeqjoinsel ));
  DESCR("matches regular expression, case-sensitive");

I've tried to execute it from the C code:

  text * s = cstring_to_text("aa");
  text * p = cstring_to_text("a");
  return DatumGetBool(DirectFunctionCall2(textregexeq, PointerGetDatum(s), PointerGetDatum(p)));

But I'm getting an error with collate:

ERROR:  could not determine which collation to use for regular expression
HINT:  Use the COLLATE clause to set the collation explicitly.
Any hints on how to proceed? Of course if I do select 'aa'~'a'; from psql it works like a charm.

Thanks in advance.

Re: [GENERAL] Executing regex in C code

От
Tom Lane
Дата:
Gabriel Furstenheim Milerud <furstenheim@gmail.com> writes:
> I'm trying to execute the equivalent to '~' with regexp from within C code.

>   text * s = cstring_to_text("aa");
>   text * p = cstring_to_text("a");
>   return DatumGetBool(DirectFunctionCall2(textregexeq, PointerGetDatum(s),
> PointerGetDatum(p)));

> But I'm getting an error with collate:
> ERROR:  could not determine which collation to use for regular expression
> HINT:  Use the COLLATE clause to set the collation explicitly.

Yes, you need to use DirectFunctionCall2Coll() if you're trying to invoke
a collation-aware function.  It's probably good enough to pass
DEFAULT_COLLATION_OID, although if you're inside a SQL function of
your own, passing down whatever collation was passed to you would
be a better plan.

            regards, tom lane

Re: [GENERAL] Executing regex in C code

От
Gabriel Furstenheim Milerud
Дата:
Thanks a lot,
That did the trick

Best regards

On 30 July 2017 at 18:26, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Gabriel Furstenheim Milerud <furstenheim@gmail.com> writes:
> I'm trying to execute the equivalent to '~' with regexp from within C code.

>   text * s = cstring_to_text("aa");
>   text * p = cstring_to_text("a");
>   return DatumGetBool(DirectFunctionCall2(textregexeq, PointerGetDatum(s),
> PointerGetDatum(p)));

> But I'm getting an error with collate:
> ERROR:  could not determine which collation to use for regular expression
> HINT:  Use the COLLATE clause to set the collation explicitly.

Yes, you need to use DirectFunctionCall2Coll() if you're trying to invoke
a collation-aware function.  It's probably good enough to pass
DEFAULT_COLLATION_OID, although if you're inside a SQL function of
your own, passing down whatever collation was passed to you would
be a better plan.

                        regards, tom lane