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Diffstat (limited to 'src/backend/utils/adt/datum.c')
-rw-r--r--src/backend/utils/adt/datum.c56
1 files changed, 37 insertions, 19 deletions
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index 7c0dbeeb49c..0a751ff1dff 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/datum.c,v 1.23 2002/06/20 20:29:37 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/datum.c,v 1.24 2002/08/24 15:00:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -19,15 +19,19 @@
* Datum itself (i.e. no pointers involved!). In this case the
* length of the type is always greater than zero and not more than
* "sizeof(Datum)"
- * B) if a type is not "byVal" and it has a fixed length, then
- * the "Datum" always contain a pointer to a stream of bytes.
- * The number of significant bytes are always equal to the length of the
- * type.
- * C) if a type is not "byVal" and is of variable length (i.e. it has
- * length == -1) then "Datum" always points to a "struct varlena".
+ *
+ * B) if a type is not "byVal" and it has a fixed length (typlen > 0),
+ * then the "Datum" always contains a pointer to a stream of bytes.
+ * The number of significant bytes are always equal to the typlen.
+ *
+ * C) if a type is not "byVal" and has typlen == -1,
+ * then the "Datum" always points to a "struct varlena".
* This varlena structure has information about the actual length of this
* particular instance of the type and about its value.
*
+ * D) if a type is not "byVal" and has typlen == -2,
+ * then the "Datum" always points to a null-terminated C string.
+ *
* Note that we do not treat "toasted" datums specially; therefore what
* will be copied or compared is the compressed data or toast reference.
*/
@@ -36,17 +40,15 @@
#include "utils/datum.h"
+
/*-------------------------------------------------------------------------
* datumGetSize
*
* Find the "real" size of a datum, given the datum value,
- * whether it is a "by value", and its length.
+ * whether it is a "by value", and the declared type length.
*
- * To cut a long story short, usually the real size is equal to the
- * type length, with the exception of variable length types which have
- * a length equal to -1. In this case, we have to look at the value of
- * the datum itself (which is a pointer to a 'varlena' struct) to find
- * its size.
+ * This is essentially an out-of-line version of the att_addlength()
+ * macro in access/tupmacs.h. We do a tad more error checking though.
*-------------------------------------------------------------------------
*/
Size
@@ -62,19 +64,33 @@ datumGetSize(Datum value, bool typByVal, int typLen)
}
else
{
- if (typLen == -1)
+ if (typLen > 0)
+ {
+ /* Fixed-length pass-by-ref type */
+ size = (Size) typLen;
+ }
+ else if (typLen == -1)
{
- /* Assume it is a varlena datatype */
+ /* It is a varlena datatype */
struct varlena *s = (struct varlena *) DatumGetPointer(value);
if (!PointerIsValid(s))
elog(ERROR, "datumGetSize: Invalid Datum Pointer");
- size = (Size) VARSIZE(s);
+ size = (Size) VARATT_SIZE(s);
+ }
+ else if (typLen == -2)
+ {
+ /* It is a cstring datatype */
+ char *s = (char *) DatumGetPointer(value);
+
+ if (!PointerIsValid(s))
+ elog(ERROR, "datumGetSize: Invalid Datum Pointer");
+ size = (Size) (strlen(s) + 1);
}
else
{
- /* Fixed-length pass-by-ref type */
- size = (Size) typLen;
+ elog(ERROR, "datumGetSize: Invalid typLen %d", typLen);
+ size = 0; /* keep compiler quiet */
}
}
@@ -159,7 +175,9 @@ datumIsEqual(Datum value1, Datum value2, bool typByVal, int typLen)
/*
* just compare the two datums. NOTE: just comparing "len" bytes
* will not do the work, because we do not know how these bytes
- * are aligned inside the "Datum".
+ * are aligned inside the "Datum". We assume instead that any
+ * given datatype is consistent about how it fills extraneous
+ * bits in the Datum.
*/
res = (value1 == value2);
}