Re: fix_PGSTAT_NUM_TABENTRIES_macro patch - Mailing list pgsql-hackers

A quick grep through the code reveals lots of examples,
so I'll just paste the first ones I notice.  There are
references to sizeof(Oid), sizeof(uint32), sizeof(bool),
and sizeof(uint8) that clearly refer to fields in structs that
the macros refer to implicitly, but there is no way for the
compiler to detect if you change the struct but not the
macro.

I see these as similar to what I was talking about in
src/include/pgstat.h.


Mark Dilger


src/include/pg_attribute.h:
------------------------------

#define ATTRIBUTE_FIXED_PART_SIZE \
    (offsetof(FormData_pg_attribute,attcollation) + sizeof(Oid))


src/include/access/tuptoaster.h:
-------------------------------------

#define MaximumBytesPerTuple(tuplesPerPage) \
    MAXALIGN_DOWN((BLCKSZ - \
                   MAXALIGN(SizeOfPageHeaderData + (tuplesPerPage) * sizeof(ItemIdData))) \
                  / (tuplesPerPage))

#define TOAST_MAX_CHUNK_SIZE    \
    (EXTERN_TUPLE_MAX_SIZE -                            \
     MAXALIGN(offsetof(HeapTupleHeaderData, t_bits)) -  \
     sizeof(Oid) -                                      \
     sizeof(int32) -                                    \
     VARHDRSZ)

src/include/access/htup.h:
------------------------------

#define HeapTupleHeaderGetOid(tup) \
( \
    ((tup)->t_infomask & HEAP_HASOID) ? \
        *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
    : \
        InvalidOid \
)

#define HeapTupleHeaderSetOid(tup, oid) \
do { \
    Assert((tup)->t_infomask & HEAP_HASOID); \
    *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) = (oid); \
} while (0)

#define MINIMAL_TUPLE_OFFSET \
    ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
#define MINIMAL_TUPLE_PADDING \
    ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
#define MINIMAL_TUPLE_DATA_OFFSET \
    offsetof(MinimalTupleData, t_infomask2)

#define SizeOfHeapDelete    (offsetof(xl_heap_delete, all_visible_cleared) + sizeof(bool))

#define SizeOfHeapHeader    (offsetof(xl_heap_header, t_hoff) + sizeof(uint8))