Consolidate VACUUM xid cutoff logic.

Push the logic for determining whether or not a VACUUM operation will be
aggressive down into vacuum_set_xid_limits().  This makes the function's
signature significantly simpler, and seems clearer overall.

Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzkymFbz6D_vL+jmqSn_5q1wsFvFrE+37yLgL_Rkfd6Gzg@mail.gmail.com

Author: petergeoghegan

src/backend/access/heap/vacuumlazy.c

@@ -323,8 +323,6 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
 				minmulti_updated;
 	BlockNumber orig_rel_pages;
 	char	  **indnames = NULL;
-	TransactionId xidFullScanLimit;
-	MultiXactId mxactFullScanLimit;
 	BlockNumber new_rel_pages;
 	BlockNumber new_rel_allvisible;
 	double		new_live_tuples;
@@ -352,24 +350,24 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
 	pgstat_progress_start_command(PROGRESS_COMMAND_VACUUM,
 								  RelationGetRelid(rel));
 
-	vacuum_set_xid_limits(rel,
-						  params->freeze_min_age,
-						  params->freeze_table_age,
-						  params->multixact_freeze_min_age,
-						  params->multixact_freeze_table_age,
-						  &OldestXmin, &FreezeLimit, &xidFullScanLimit,
-						  &MultiXactCutoff, &mxactFullScanLimit);
-
 	/*
-	 * We request an aggressive scan if the table's frozen Xid is now older
-	 * than or equal to the requested Xid full-table scan limit; or if the
-	 * table's minimum MultiXactId is older than or equal to the requested
-	 * mxid full-table scan limit; or if DISABLE_PAGE_SKIPPING was specified.
+	 * Get OldestXmin cutoff, which is used to determine which deleted tuples
+	 * are considered DEAD, not just RECENTLY_DEAD.  Also get related cutoffs
+	 * used to determine which XIDs/MultiXactIds will be frozen.
+	 *
+	 * If this is an aggressive VACUUM, then we're strictly required to freeze
+	 * any and all XIDs from before FreezeLimit, so that we will be able to
+	 * safely advance relfrozenxid up to FreezeLimit below (we must be able to
+	 * advance relminmxid up to MultiXactCutoff, too).
 	 */
-	aggressive = TransactionIdPrecedesOrEquals(rel->rd_rel->relfrozenxid,
-											   xidFullScanLimit);
-	aggressive |= MultiXactIdPrecedesOrEquals(rel->rd_rel->relminmxid,
-											  mxactFullScanLimit);
+	aggressive = vacuum_set_xid_limits(rel,
+									   params->freeze_min_age,
+									   params->freeze_table_age,
+									   params->multixact_freeze_min_age,
+									   params->multixact_freeze_table_age,
+									   &OldestXmin, &FreezeLimit,
+									   &MultiXactCutoff);
+
 	skipwithvm = true;
 	if (params->options & VACOPT_DISABLE_PAGE_SKIPPING)
 	{

src/backend/commands/cluster.c

@@ -857,8 +857,7 @@ copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose,
 	 * not to be aggressive about this.
 	 */
 	vacuum_set_xid_limits(OldHeap, 0, 0, 0, 0,
-						  &OldestXmin, &FreezeXid, NULL, &MultiXactCutoff,
-						  NULL);
+						  &OldestXmin, &FreezeXid, &MultiXactCutoff);
 
 	/*
 	 * FreezeXid will become the table's new relfrozenxid, and that mustn't go

src/backend/commands/vacuum.c

@@ -943,34 +943,26 @@ get_all_vacuum_rels(int options)
  * Input parameters are the target relation, applicable freeze age settings.
  *
  * The output parameters are:
- * - oldestXmin is the cutoff value used to distinguish whether tuples are
- *	 DEAD or RECENTLY_DEAD (see HeapTupleSatisfiesVacuum).
+ * - oldestXmin is the Xid below which tuples deleted by any xact (that
+ *   committed) should be considered DEAD, not just RECENTLY_DEAD.
  * - freezeLimit is the Xid below which all Xids are replaced by
  *	 FrozenTransactionId during vacuum.
- * - xidFullScanLimit (computed from freeze_table_age parameter)
- *	 represents a minimum Xid value; a table whose relfrozenxid is older than
- *	 this will have a full-table vacuum applied to it, to freeze tuples across
- *	 the whole table.  Vacuuming a table younger than this value can use a
- *	 partial scan.
- * - multiXactCutoff is the value below which all MultiXactIds are removed from
- *	 Xmax.
- * - mxactFullScanLimit is a value against which a table's relminmxid value is
- *	 compared to produce a full-table vacuum, as with xidFullScanLimit.
+ * - multiXactCutoff is the value below which all MultiXactIds are removed
+ *   from Xmax.
  *
- * xidFullScanLimit and mxactFullScanLimit can be passed as NULL if caller is
- * not interested.
+ * Return value indicates if vacuumlazy.c caller should make its VACUUM
+ * operation aggressive.  An aggressive VACUUM must advance relfrozenxid up to
+ * FreezeLimit, and relminmxid up to multiXactCutoff.
  */
-void
+bool
 vacuum_set_xid_limits(Relation rel,
 					  int freeze_min_age,
 					  int freeze_table_age,
 					  int multixact_freeze_min_age,
 					  int multixact_freeze_table_age,
 					  TransactionId *oldestXmin,
 					  TransactionId *freezeLimit,
-					  TransactionId *xidFullScanLimit,
-					  MultiXactId *multiXactCutoff,
-					  MultiXactId *mxactFullScanLimit)
+					  MultiXactId *multiXactCutoff)
 {
 	int			freezemin;
 	int			mxid_freezemin;
@@ -980,6 +972,7 @@ vacuum_set_xid_limits(Relation rel,
 	MultiXactId oldestMxact;
 	MultiXactId mxactLimit;
 	MultiXactId safeMxactLimit;
+	int			freezetable;
 
 	/*
 	 * We can always ignore processes running lazy vacuum.  This is because we
@@ -1097,64 +1090,60 @@ vacuum_set_xid_limits(Relation rel,
 
 	*multiXactCutoff = mxactLimit;
 
-	if (xidFullScanLimit != NULL)
-	{
-		int			freezetable;
-
-		Assert(mxactFullScanLimit != NULL);
-
-		/*
-		 * Determine the table freeze age to use: as specified by the caller,
-		 * or vacuum_freeze_table_age, but in any case not more than
-		 * autovacuum_freeze_max_age * 0.95, so that if you have e.g nightly
-		 * VACUUM schedule, the nightly VACUUM gets a chance to freeze tuples
-		 * before anti-wraparound autovacuum is launched.
-		 */
-		freezetable = freeze_table_age;
-		if (freezetable < 0)
-			freezetable = vacuum_freeze_table_age;
-		freezetable = Min(freezetable, autovacuum_freeze_max_age * 0.95);
-		Assert(freezetable >= 0);
-
-		/*
-		 * Compute XID limit causing a full-table vacuum, being careful not to
-		 * generate a "permanent" XID.
-		 */
-		limit = ReadNextTransactionId() - freezetable;
-		if (!TransactionIdIsNormal(limit))
-			limit = FirstNormalTransactionId;
+	/*
+	 * Done setting output parameters; just need to figure out if caller needs
+	 * to do an aggressive VACUUM or not.
+	 *
+	 * Determine the table freeze age to use: as specified by the caller, or
+	 * vacuum_freeze_table_age, but in any case not more than
+	 * autovacuum_freeze_max_age * 0.95, so that if you have e.g nightly
+	 * VACUUM schedule, the nightly VACUUM gets a chance to freeze tuples
+	 * before anti-wraparound autovacuum is launched.
+	 */
+	freezetable = freeze_table_age;
+	if (freezetable < 0)
+		freezetable = vacuum_freeze_table_age;
+	freezetable = Min(freezetable, autovacuum_freeze_max_age * 0.95);
+	Assert(freezetable >= 0);
 
-		*xidFullScanLimit = limit;
+	/*
+	 * Compute XID limit causing an aggressive vacuum, being careful not to
+	 * generate a "permanent" XID
+	 */
+	limit = ReadNextTransactionId() - freezetable;
+	if (!TransactionIdIsNormal(limit))
+		limit = FirstNormalTransactionId;
+	if (TransactionIdPrecedesOrEquals(rel->rd_rel->relfrozenxid,
+									  limit))
+		return true;
 
-		/*
-		 * Similar to the above, determine the table freeze age to use for
-		 * multixacts: as specified by the caller, or
-		 * vacuum_multixact_freeze_table_age, but in any case not more than
-		 * autovacuum_multixact_freeze_table_age * 0.95, so that if you have
-		 * e.g. nightly VACUUM schedule, the nightly VACUUM gets a chance to
-		 * freeze multixacts before anti-wraparound autovacuum is launched.
-		 */
-		freezetable = multixact_freeze_table_age;
-		if (freezetable < 0)
-			freezetable = vacuum_multixact_freeze_table_age;
-		freezetable = Min(freezetable,
-						  effective_multixact_freeze_max_age * 0.95);
-		Assert(freezetable >= 0);
+	/*
+	 * Similar to the above, determine the table freeze age to use for
+	 * multixacts: as specified by the caller, or
+	 * vacuum_multixact_freeze_table_age, but in any case not more than
+	 * autovacuum_multixact_freeze_table_age * 0.95, so that if you have e.g.
+	 * nightly VACUUM schedule, the nightly VACUUM gets a chance to freeze
+	 * multixacts before anti-wraparound autovacuum is launched.
+	 */
+	freezetable = multixact_freeze_table_age;
+	if (freezetable < 0)
+		freezetable = vacuum_multixact_freeze_table_age;
+	freezetable = Min(freezetable,
+					  effective_multixact_freeze_max_age * 0.95);
+	Assert(freezetable >= 0);
 
-		/*
-		 * Compute MultiXact limit causing a full-table vacuum, being careful
-		 * to generate a valid MultiXact value.
-		 */
-		mxactLimit = ReadNextMultiXactId() - freezetable;
-		if (mxactLimit < FirstMultiXactId)
-			mxactLimit = FirstMultiXactId;
+	/*
+	 * Compute MultiXact limit causing an aggressive vacuum, being careful to
+	 * generate a valid MultiXact value
+	 */
+	mxactLimit = ReadNextMultiXactId() - freezetable;
+	if (mxactLimit < FirstMultiXactId)
+		mxactLimit = FirstMultiXactId;
+	if (MultiXactIdPrecedesOrEquals(rel->rd_rel->relminmxid,
+									mxactLimit))
+		return true;
 
-		*mxactFullScanLimit = mxactLimit;
-	}
-	else
-	{
-		Assert(mxactFullScanLimit == NULL);
-	}
+	return false;
 }
 
 /*

src/include/commands/vacuum.h

@@ -286,15 +286,13 @@ extern void vac_update_relstats(Relation relation,
 								bool *frozenxid_updated,
 								bool *minmulti_updated,
 								bool in_outer_xact);
-extern void vacuum_set_xid_limits(Relation rel,
+extern bool vacuum_set_xid_limits(Relation rel,
 								  int freeze_min_age, int freeze_table_age,
 								  int multixact_freeze_min_age,
 								  int multixact_freeze_table_age,
 								  TransactionId *oldestXmin,
 								  TransactionId *freezeLimit,
-								  TransactionId *xidFullScanLimit,
-								  MultiXactId *multiXactCutoff,
-								  MultiXactId *mxactFullScanLimit);
+								  MultiXactId *multiXactCutoff);
 extern bool vacuum_xid_failsafe_check(TransactionId relfrozenxid,
 									  MultiXactId relminmxid);
 extern void vac_update_datfrozenxid(void);