Getting char * from timestamp in a composite type
Hi,
I need to extract a text string representation of a timestamp from a
user-defined row type; e.g., from the composite type ('1980-01-01
12:00:00', 'Random Comment'), I'd like to extract the C string
1980-01-01 12:00:00 in my user-defined C function.
As I understand it, I should be able to do something like (assuming
"time" is the attribute name):
bool isNull;
HeapTupleHeader t = DatumGetHeapTupleHeader(row);
Datum var = GetAttributeByName( row, "time", & isNull );
// Check for null
char * ret = DatumGetCString( DirectFunctionCall1(textout, var ) );
However, the code above (and every other variant I've tried) invariable
segmentation faults the postmaster. so obviously I am doing something
wrong. Can someone explain (or point to an example that works) of how to
do this?
Regards,
Michael A.
On Wed, Dec 19, 2007 at 04:40:38PM +0100, Michael Akinde wrote:
As I understand it, I should be able to do something like (assuming
"time" is the attribute name):bool isNull;
HeapTupleHeader t = DatumGetHeapTupleHeader(row);
Datum var = GetAttributeByName( row, "time", & isNull );
// Check for null
char * ret = DatumGetCString( DirectFunctionCall1(textout, var ) );
That's not going to work. textout wants a text datum. Try calling
timestamp_out instead...
Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
Show quoted text
Those who make peaceful revolution impossible will make violent revolution inevitable.
-- John F Kennedy
Martijn van Oosterhout wrote:
On Wed, Dec 19, 2007 at 04:40:38PM +0100, Michael Akinde wrote:
As I understand it, I should be able to do something like (assuming
"time" is the attribute name):bool isNull;
HeapTupleHeader t = DatumGetHeapTupleHeader(row);
Datum var = GetAttributeByName( row, "time", & isNull );
// Check for null
char * ret = DatumGetCString( DirectFunctionCall1(textout, var ) );That's not going to work. textout wants a text datum. Try calling
timestamp_out instead..
Sigh... it's always the idiot bugs that are the hardest to see. Thanks a
lot.
Regards,
Michael A.
Michael Akinde <michael.akinde@met.no> writes:
bool isNull;
HeapTupleHeader t = DatumGetHeapTupleHeader(row);
Datum var = GetAttributeByName( row, "time", & isNull );
// Check for null
char * ret = DatumGetCString( DirectFunctionCall1(textout, var ) );That's not going to work. textout wants a text datum. Try calling
timestamp_out instead..Sigh... it's always the idiot bugs that are the hardest to see. Thanks a
lot.
The other problem is that you're passing row not t to
GetAttributeByName. If you don't have your compiler configured to bleat
about type mismatches like that, your days of C programming will be
bleak and painful.
regards, tom lane
Thanks, though that was an error caused by my attempt to copy-paste some
readable example of code from the source file.
Matching the correct _out functions in the DirectFunctionCall fixed the
segmentation fault problems I was seeing.
Regards,
Michael A.
Tom Lane wrote:
Show quoted text
Michael Akinde <michael.akinde@met.no> writes:
bool isNull;
HeapTupleHeader t = DatumGetHeapTupleHeader(row);
Datum var = GetAttributeByName( row, "time", & isNull );
// Check for null
char * ret = DatumGetCString( DirectFunctionCall1(textout, var ) );That's not going to work. textout wants a text datum. Try calling
timestamp_out instead..Sigh... it's always the idiot bugs that are the hardest to see. Thanks a
lot.The other problem is that you're passing row not t to
GetAttributeByName. If you don't have your compiler configured to bleat
about type mismatches like that, your days of C programming will be
bleak and painful.regards, tom lane