Function plpgsql_build_recfield

src/pl/plpgsql/src/pl_comp.c:2063–2096

* Build a RECFIELD datum for the named field of the specified record variable * * If there's already such a datum, just return it; we don't need duplicates. */

 * If there's already such a datum, just return it; we don't need duplicates.
 */
PLpgSQL_recfield *
plpgsql_build_recfield(PLpgSQL_rec *rec, const char *fldname)
{
	PLpgSQL_recfield *recfield;
	int			i;

	/* search for an existing datum referencing this field */
	i = rec->firstfield;
	while (i >= 0)
	{
		PLpgSQL_recfield *fld = (PLpgSQL_recfield *) plpgsql_Datums[i];

		Assert(fld->dtype == PLPGSQL_DTYPE_RECFIELD &&
			   fld->recparentno == rec->dno);
		if (strcmp(fld->fieldname, fldname) == 0)
			return fld;
		i = fld->nextfield;
	}

	/* nope, so make a new one */
	recfield = palloc0(sizeof(PLpgSQL_recfield));
	recfield->dtype = PLPGSQL_DTYPE_RECFIELD;
	recfield->fieldname = pstrdup(fldname);
	recfield->recparentno = rec->dno;
	recfield->rectupledescid = INVALID_TUPLEDESC_IDENTIFIER;

	plpgsql_adddatum((PLpgSQL_datum *) recfield);

	/* now we can link it into the parent's chain */
	recfield->nextfield = rec->firstfield;
	rec->firstfield = recfield->dno;

	return recfield;
}

/*
 * plpgsql_build_datatype