diff options
Diffstat (limited to 'src/backend/utils/adt/datum.c')
-rw-r--r-- | src/backend/utils/adt/datum.c | 56 |
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); } |