Function CacheInvalidateHeapTuple

src/backend/utils/cache/inval.c:1204–1337

* CacheInvalidateHeapTuple * Register the given tuple for invalidation at end of command * (ie, current command is creating or outdating this tuple). * Also, detect whether a relcache invalidation is implied. * * For an insert or delete, tuple is the target tuple and newtuple is NULL. * For an update, we are called just once, with tuple being the old tuple * version and newtuple the new

 * effort during an update.
 */
void
CacheInvalidateHeapTuple(Relation relation,
						 HeapTuple tuple,
						 HeapTuple newtuple)
{
	Oid			tupleRelId;
	Oid			databaseId;
	Oid			relationId;

	/* Do nothing during bootstrap */
	if (IsBootstrapProcessingMode())
		return;

	/*
	 * We only need to worry about invalidation for tuples that are in system
	 * catalogs; user-relation tuples are never in catcaches and can't affect
	 * the relcache either.
	 */
	if (!IsCatalogRelation(relation))
		return;

	/*
	 * IsCatalogRelation() will return true for TOAST tables of system
	 * catalogs, but we don't care about those, either.
	 */
	if (IsToastRelation(relation))
		return;

	/*
	 * If we're not prepared to queue invalidation messages for this
	 * subtransaction level, get ready now.
	 */
	PrepareInvalidationState();

	/*
	 * First let the catcache do its thing
	 */
	tupleRelId = RelationGetRelid(relation);
	if (RelationInvalidatesSnapshotsOnly(tupleRelId))
	{
		databaseId = IsSharedRelation(tupleRelId) ? InvalidOid : MyDatabaseId;
		RegisterSnapshotInvalidation(databaseId, tupleRelId);
	}
	else
		PrepareToInvalidateCacheTuple(relation, tuple, newtuple,
									  RegisterCatcacheInvalidation);

	/*
	 * Now, is this tuple one of the primary definers of a relcache entry? See
	 * comments in file header for deeper explanation.
	 *
	 * Note we ignore newtuple here; we assume an update cannot move a tuple
	 * from being part of one relcache entry to being part of another.
	 */
	if (tupleRelId == RelationRelationId)
	{
		Form_pg_class classtup = (Form_pg_class) GETSTRUCT(tuple);