Function table_scan_sample_next_tuple

src/include/access/tableam.h:2309–2323

* Fetch the next sample tuple into `slot` and return true if a visible tuple * was found, false otherwise. table_scan_sample_next_block() needs to * previously have selected a block (i.e. returned true), and no previous * table_scan_sample_next_tuple() for the same block may have returned false. * * This will call the TsmRoutine's NextSampleTuple() callback. */

 * This will call the TsmRoutine's NextSampleTuple() callback.
 */
static inline bool
table_scan_sample_next_tuple(TableScanDesc scan,
							 struct SampleScanState *scanstate,
							 TupleTableSlot *slot)
{
	/*
	 * We don't expect direct calls to table_scan_sample_next_tuple with valid
	 * CheckXidAlive for catalog or regular tables.  See detailed comments in
	 * xact.c where these variables are declared.
	 */
	if (unlikely(TransactionIdIsValid(CheckXidAlive) && !bsysscan))
		elog(ERROR, "unexpected table_scan_sample_next_tuple call during logical decoding");
	return scan->rs_rd->rd_tableam->scan_sample_next_tuple(scan, scanstate,
														   slot);
}


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