Week 04 Lectures (25)

PostgreSQL Attribute Values (cont)

Attribute values can be extracted as Datum from HeapTuples

Datum heap_getattr(
      HeapTuple tup,     // tuple (in memory)
      int attnum,        // which attribute
      TupleDesc tupDesc, // field descriptors
      bool *isnull       // flag to record NULL
)

isnull is set to true if value of field is NULL

attnum can be negative ... to access system attributes (e.g. OID)

For details, see include/access/htup_details.h