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Add comments describing interface to heap_getattr().

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Bryan Henderson 1996-12-09 01:22:17 +00:00
parent 6cfb12e0cf
commit b36e3042e7
1 changed files with 30 additions and 21 deletions
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51
src/backend/access/common/heaptuple.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.17 1996/12/04 03:05:55 bryanh Exp $
* $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.18 1996/12/09 01:22:17 bryanh Exp $
*
* NOTES
* The old interface functions have been converted to macros
@ -658,52 +658,61 @@ fastgetattr(HeapTuple tup,
}
/* ----------------
* heap_getattr
* heap_getattr
*
* returns an attribute from a heap tuple. uses
* ----------------
*/
* Find a particular field in a row represented as a heap tuple.
* We return a pointer into that heap tuple, which points to the
* first byte of the value of the field in question.
*
* If the field in question has a NULL value, we return a null
* pointer and return <*isnull> == true. Otherwise, we return
* <*isnull> == false.
*
* <tup> is the pointer to the heap tuple. <attnum> is the attribute
* number of the column (field) caller wants. <tupleDesc> is a
* pointer to the structure describing the row and all its fields.
* ---------------- */
char *
heap_getattr(HeapTuple tup,
Buffer b,
int attnum,
TupleDesc tupleDesc,
bool *isnull)
Buffer b,
int attnum,
TupleDesc tupleDesc,
bool *isnull)
{
bool localIsNull;
bool localIsNull;
/* ----------------
* sanity checks
* sanity checks
* ----------------
*/
Assert(tup != NULL);
if (! PointerIsValid(isnull))
isnull = &localIsNull;
isnull = &localIsNull;
if (attnum > (int) tup->t_natts) {
*isnull = true;
return ((char *) NULL);
*isnull = true;
return ((char *) NULL);
}
/* ----------------
* take care of user defined attributes
* take care of user defined attributes
* ----------------
*/
if (attnum > 0) {
char *datum;
datum = fastgetattr(tup, attnum, tupleDesc, isnull);
return (datum);
char *datum;
datum = fastgetattr(tup, attnum, tupleDesc, isnull);
return (datum);
}
/* ----------------
* take care of system attributes
* take care of system attributes
* ----------------
*/
*isnull = false;
return
heap_getsysattr(tup, b, attnum);
heap_getsysattr(tup, b, attnum);
}
/* ----------------