/* Typedef for callback function for table_index_build_scan */
typedef void (*IndexBuildCallback) (Relation index,
ItemPointer tid,
Datum
*values,
bool
*isnull,
bool
tupleIsAlive,
void
*state);
When we build an index on an existed heap table, so pg will read the tuple one
by one and give the tuple’s hepatid as this ItemPointer, is that right?