Writing and Reading bytea

We need insert rows to a catalog table that would store partitions info:

CATALOG(pg_partition,2336) BKI_WITHOUT_OIDS
{   Oid         partrelid;      /* partition table Oid */   Oid         parentrelid;    /* Parent table Oid */   int2
    parttype;       /* Type of partition, list, hash, range */   int2        partkey;        /* partition key */   Oid
      keytype;        /* type of partition key */   int2        keyorder;       /* order of the key in multi-key
partitions*/   bytea       minval;   bytea       maxval;             /* min and max for range partition */   bytea
listval;   int2        hashval;            /* hash value */
 
} FormData_pg_partition;



The following code is used to write bytea:   ...   min_ba = (bytea *) palloc(len+VARHDRSZ);   memcpy(VARDATA(min_ba),
&b_min,len);   SET_VARSIZE(min_ba, len+VARHDRSZ);   values[Anum_pg_partition_minval        -1]= (Datum)min_ba ;
 
...   Relation r = heap_open(PartitionRelationId, RowExclusiveLock);  TupleDesc tupDesc = r->rd_att;   HeapTuple tup =
heap_form_tuple(tupDesc,values, nulls);   simple_heap_insert(r, tup);   CatalogUpdateIndexes(r, tup);   heap_close(r,
RowExclusiveLock);

We can see the correct bytes in the pg_partition table after exectuing
the above code. However, retrieving the bytea datatypes seems
problematic.
The following code didn't work:
....   pg_partrel = heap_open(PartitionRelationId, AccessShareLock);   pg_partscan = systable_beginscan(pg_partrel,
PartitionParentIndexId,true,                               SnapshotNow, 1, &skey);   while
(HeapTupleIsValid(pg_parttup=systable_getnext(pg_partscan)))   {       Form_pg_partition pg_part = (Form_pg_partition)
GETSTRUCT(pg_parttup);      Datum attr = heap_getattr(tuple, pg_part->partkey, rel->rd_att, &isnull)       Datum
min_part_attr= (Datum) (&pg_part->minval);       Datum max_part_attr = (Datum) (&pg_part->maxval); ......
 

}

max_part_attr is not poining to right mem location.  After doing some
investgation, we found since minval extends to 10 bytes (instead of 5
bytes occupied by struct varlena), max_part_attr value is not correct.
We also tried doing a hack:
max_ part_attr = (Datum)
(((void*)(&pg_part->minval))+VARSIZE_ANY(&pg_part->minval));

but still we are facing problems.

Any pointers in this respect will be helpful.

Thanks,
Amit
Persistent Systems